PBDJ 11-5Y - SYS

Transcription

PBDJ 11-5Y - SYS

CREATING WEB APPS FOR MOBILE DEVICES
pg. 4
U.S. $15.00 (CANADA $16.00)
FEBRUARY 2005 - Volume: 12 Issue: 2
www.sys-con.com/pbdj
From the Editor
Eating Your Own
Dog Food
The res u l ts o f t h e la t es t p o ll b y
N o v a l y s o n P o w e r B u i l d e r u s e a re in.
The res ults are g o o d .
by Bruce Armstrong pg. 3
Industry Announcements
by Bruce Armstrong pg. 34
D a t a Wi n d o w.NET is a nom ine e in
pg.22
t h e 2 0 0 5 . N E T D e v e l o p e r ’s J o u r n a l
R e a d e r s ’ C h o i c e Aw a r d s i n t h e
l i b r a r i e s a n d c o n t r o l s c a t e g o r y.
pg.14
•••
Relavis Corporation has selected the
iAnywhere P y l o n A p p l i c a t i o n S e r v e r
to power its soon-to-be re l e a s e d
eSales Mobile application.
•••
Mobile Apps: Unwired Accelerator
in Action Not just mobility development
Berndt Hamboeck
4
S yb a s e re p o r t e d t o t a l l i c en s e
revenues i ncre a s e d 7 % f o r
the four th quar te r e nd e d
December 31, 2004.
•••
Sybase announced the availability
Techniques: About Surrogate
and Natural Keys
When are they approriate in a data model?
Mike Nicewarner
10
of its re l a t i o n a l d a t a b a s e
management system, Sybase
Adaptive Ser ver Enterprise for
L i n u x o n I B M ’s e S e r v e r
OpenPower systems.
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Feature: Taking PowerBuilder’s
PBDOM Out for a Spin
Book Excerpt: EAServer
Problem Analysis & Troubleshooting
Part art, part science PART I
Dropdown Filtering: Dynamic Web
Page Content… Without refreshing the page
Arthur Hefti
14
Jim O’Neil
18
Rahul Jain
28
FROM THE EDITOR
EDITORIAL ADVISORY BOARD
Eating Your Own Dog Food
BRUCE ARMSTRONG, MICHAEL BARLOTTA, ANDY BLUM,
KOUROS GORGANI, BAHADIR KARUV, PhD,
BERNIE METZGER, JOHN OLSON, SEAN RHODY, IAN THAIN
EDITOR-IN-CHIEF:
EXECUTIVE EDITOR:
ASSISTANT EDITOR:
ONLINE EDITOR:
CONTRIBUTING EDITOR:
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RESEARCH EDITOR:
BRUCE ARMSTRONG
NANCY VALENTINE
SETA PAPAZIAN
MARTIN WEZDECKI
JOHN OLSON
BRUCE ARMSTRONG
RICHARD BROOKS
BAHADIR KARUV, PhD
WRITERS IN THIS ISSUE
BRUCE ARMSTRONG, BERNDT HAMBOECK, ARTHUR HEFTI,
RAHUL JAIN, MIKE NICEWARNER, JIM O’NEIL
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BRUCE ARMSTRONG
ou might remember from my TechWave 2004 notes, “eating your own
dog food” is my favorite means of
describing a company using its own products in its public interface to their customers
(e.g., their Web site). If a company expects
their customers to put faith in the utility
and stability of the product, they should be
showing that same confidence in the product themselves.
Y
I also mentioned in last month’s editorial that the Audiovox SMT5600 I’m now
using and the Motorola MPX220 both use
the mini-SD card rather than a standardsized SD memory card. If you’re as unfamiliar as I was with the mini-SD card at that
time, you may not realize that the mini-SD
card comes with an adapter that will allow
it to work in a standard SD slot. Pretty slick.
PowerBuilder Use Survey Results
Well, we have another excellent example
of Sybase doing that. Are you familiar with
the search engine on Sybase? No, not that
search engine! That was the old one that
ran slowly and gave you useless results.
Sybase recently replaced that with a search
engine built on EAServer accessing data
stored in Adaptive Server Enterprise
(which, incidentally, is the same technology
combination I used for the newsgroup
search engine on teamsybase.com, but I
digress…). The end result is search results
that come back quickly and are actually
highly relevant. Perhaps Sybase could sell
the solution to Microsoft’s MSDN site,
which could certainly use it.
SmartPhone Review
The folks at eWeek just did a review of the
Motorola MPX220 that I was so hot for a while
back (they also reviewed one Palm and one
BlackBerry device). One interesting note from
their review was the following: “We’d love to
see smartphone hardware and software vendors license SureType from RIM for inclusion
in their products – the technology represents
one of the best new ideas in mobile device
input that we’ve seen in some time.”
As I indicated in my last comments on
the smartphone platform, the key hurdle is
user input. It sounds like BlackBerry has
come up with an advance in that area. Most
phones use the same letter-to-number key
assignments as a house phone, which
requires anywhere from two to four key
presses to obtain a single correct letter. The
BlackBerry keyboard uses a standard
QWERTY typewriter layout, with only one
or two letters assigned to each key, making
it much easier for the predictive software to
guess which letter you are trying to type.
The results of the latest poll by Novalys on
PowerBuilder use are in. The results are good.
A lot of people are still using PowerBuilder
and intend to continue doing so for some
time. An increasing number are using PowerBuilder to do new development work, rather
than simply maintaining existing applications. The number of developers on a particular project has increased over previous years.
What I found particularly interesting is
that the majority of people are using
PowerBuilder versions 8 and 9. Only slightly
over 1% of the respondents indicated they
were using version 10. Perhaps Unicode
support was not as important as was first
thought. Hopefully, version 11 will offer
some more compelling reasons to migrate.
Note that half the respondents indicated
they will upgrade in the next year, so that
may indicate people moving to version 10,
just not that quickly.
Web Services Changes
The W3C and OASIS have a number of
new standards for Web services. The one of
particular interest to PowerBuilder developers will be XOP (XML-binary Optimized
Packaging), a standard means of transmitting binary data via XML. The others –
MTOM (Message Transformation Optimization Mechanism) and RRSHB
(Resource Representation SOAP Header
Block) – are more under-the-cover implementations to improve performance.
Unfortunately, the other key headache for
Web services developers is security, and
those bodies are only starting to develop a
common consensus on a new standard in
that area.
~continued on page 8~
[email protected]
AUTHOR BIO
Bruce Armstrong is a senior programmer with Integrated Data Services (www.get-integrated.com). A member of TeamSybase,
he has been using PowerBuilder since version 1.0.B. He was a contributing author to SYS-CON’s PowerBuilder 4.0
Secrets of the Masters and the editor of SAMs’ PowerBuilder 9: Advanced Client/Server Development.
www.SYS-CON.COM/pbdj/
PBDJ volume12 issue 2
3
MOBILE APPS
Unwired Accelerator in Action
WRITTEN BY
BERNDT
HAMBOECK
Not just mobility development
ybase doesn’t just offer PocketBuilder for mobile development.
Last month, we talked about Afaria
and Unwired Accelerator, what they’re
good for and how they might be used.
This month we’ll take a closer look at
Unwired Accelerator, install it and build
a simple example with it. No coding will
be required.
S
Introduction
For those who missed the last issue, I
will recap what Sybase Unwired Accelerator is:
• First off, it’s a rapid mobilization
solution. When Sybase says, “What
used to take months, now takes
hours,” it happens to be true.
• It’s got RAD tools to accelerate mobilizing Web applications, intranets,
portals, databases, XML and Web
services.
• It supports connected access from
BlackBerrys,
PocketPCs,
WAPenabled phones, laptops and tablets.
• It supports disconnected access
from BlackBerrys and when used
with M-Business Anywhere, another
Sybase product, disconnected access
from PocketPCs, Palm devices and
tablets.
• It’s a superset of Sybase Enterprise
Portal (and contains EP-Information
Edition and all the Mobile capabilities).
• You’ll get the big picture and what’s
possible with Unwired Accelerator in
Figure 1.
tem32\drivers\etc\hosts file called
demo.sybase.com.
Start the portal and sample databases by using the startdb.bat file. Pick up
the Tomcat server by using starttomcat.bat.
Now open your browser and go to
the URL: http://demo.sybase.com:
4040/onepage/index.html
You should see a login window. Log
in with the user name masuper and the
password m8super, and click the Login
button. What you see are the default
entries for the Mobile Web Studio
account with administrative privileges.
Once we’re logged into the Mobile Web
Studio, we can start developing our
application. There are several options
on the left side (see Figure 2):
1. The Build menu includes:
• Applications – create, edit, delete
and manage applications and their
content. They are dynamic and
reusable components (also called
portlets) that capture and deliver
any information we want to define to
our end users for using the portal or
a wireless device. The data might be
any source like Web content from
another web site, XML feeds, database query results, JavaServer Pages
or data from a corporate SAP system.
• Templates – define the organization
of applications with more than one
element, where applications are
located, background HTML code
and so on. You can apply the templates you create to applications.
Templates help applications display
on specific device types. You can
assign a different template for each
device type for a given application.
• Catalogs – here we create userdefined hierarchies of content to display in an application. When our
portal users choose to add a portlet
in the Portal Interface, they can
browse through the catalog and add
portlets of their choosing to their
personal pages and page groups.
• Pages – here we create, edit, delete
and manage the Portal Interface
pages on which the applications display.
• Page Groups – this is the place to
create, edit, delete and manage page
groups to group and organize Portal
Interface application pages.
• Composite Apps – create virtual Web
applications using several existing
applications.
2. Automate menu objects on the Auto-
Installing and Starting
AUTHOR BIO
Berndt Hamboeck is a
senior consultant for
BHITCON (www.bhit
con.net). He’s a CSI,
SCAPC8, EASAC, and
SCJP2 and started his
Sybase development
using PB5.
4
To get an evaluation copy go to
eshop.sybase.com and pick Unwired
Accelerator 6.5 with Windows 2000 as
the platform (feel free to use the Linux
version, but my step-by-step description uses the Windows version). The
download is about 80MB. The install is
pretty simple, just unzip the file and
add an entry to your WinNT\sys-
FIGURE 1 | UA in action
©2003 Sybase, Inc. All rights reserved. All trademarks are the property of their respective owners.
4GL RAD Tools
HE SAYS J2EE.
SHE SAYS .NET.
YOU SAY POWERBUILDER
PowerBuilder ® 9.0 gives you the power
and flexibility to create applications for
the platform of your choice in today’s
heterogeneous environments. You’ll find
new RAD JavaServer TM Pages, tools for
Web Services, third-party application
server support and more. Get the power
you need to develop and integrate
new Web, n-tier and rich-client apps.
Technical details are waiting for you
now at sybase.com/powerbuilder.
INFORMATION LIQUIDITY.
SYBASE INTEGRATION TECHNOLOGIES.
E V E R Y T H I N G W O R K S B E T T E R W H E N E V E R Y T H I N G W O R K S T O G E T H E R .TM
FIGURE 2 |
Mobile Web
Studio menu
mate menu include:
• Agents – they allow us to schedule or
externally trigger the automatic processing (for example by SMS or email) of a portlet’s content.
• Adapters – they’re needed if we want
to write a portlet’s content to a file,
an e-mail message or a database
table. When the agent is triggered,
the adapter interface would write the
associated portlet’s content to wherever we want (maybe into a database).
• Servers – agents have to run on agent
servers. During the installation, the
default agent server is created by the
portal. All agents run on the default
agent server unless we assign them to
a different agent server – look in tomcat\webapps\onepage\config\global.properties.xml for the property
AgentServerID, another interesting
file if you want to reconfigure the
portal to use your own brands, styles
or messages (styles.xml, css.css and
messages.xml).
3. The Manage menu includes:
• Users/Roles – edit users and manage
the resource with which they’re associated. Create, edit and manage the
roles, and assign roles to users.
• Personalization – create and manage
keys that let users personalize applications.
• M-Business – deploy applications to
M-Business Server groups, channels
and users, and perform the M-Business Anywhere administration tasks
specifically required by Mobile Web
Studio.
Building an Application
Now it’s time to start to write a simple application that users can see from
a mobile device. We’re going to build it
from an existing Web application (try
http://<your machineneame>:4040/
custview/Search.jsp and enter any
username and password combination
to log in to the sample app included in
Unwired Accelerator).
The steps for creating the mobile
application using Web Studio include:
• Create the application with a Web element using the Application Builder
wizard, save it and give it a name,
access privileges and additional configuration details. We will also approve
it to make it available for the public.
• Add the application to a page and
add this page to an existing page
group so our mobile users can call
the page using, say, Pocket Internet
Explorer.
6
CREATE A WEB ELEMENT USING THE APPLICATION BUILDER
Action Result
1. Select Applications in the left
pane, select New under Application Manager Status, and click
the New button to launch Application Builder. Click Add to create
a Web Element.
Enter the URL of the included
web application and login using
any username and password. Now
enter one of the three company
names as search cryteria:
Wells Fargo
Oracle
Morgan Stanley
And click the Find button. Then
click next in the upper right corner.
Result
You see the New Web Element window including the search
result of the included Web application. When we move the
mouse over the table with the data it changes so that we
see that it is the right place to click it.
2. Place the cursor over any site
entry in the table, and click the
mouse.
The screen refreshes showing
various presentation styles. Just
take the first one by clicking the
select button on the left and the
next button on the right upper
corner and a second time the next
button to skip the split config
window.
Click “Records contain labels.”
The “Labels are displayed in
Record” option displays. Accept
the default 1 for the row.
3. Click Next. The Filter window displays.
On the Filter window, define a
filter rule that only fields 1–3 are
displayed:
Under Add Filter Rule, select
“Include fields” from the dropdown list.
Select “number” from the number/label drop-down list.
Enter 1-3 in the value.
Click Add.
Fields 1, 2, and 3 are highlighted in the Preview section,
and the new rule
appears under the
Current Filter
Rules section. Feel
free to add a second rule for
example to
change the label
by using “edit
record” from the
drop-down list
and label as field.
4. Click Next. The parameter definition window displays. Again click
Next to bypass the window. The
Window Preview window displays.
In Element Name, enter customerSites as the Web element name
and click Next and Finish. This
brings us back to the Application
builder. Click Save and enter customerSites for the name.
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After clicking the Finish button we
can close the Application builder and
we’re back in the Web Studio. Now it’s
time to set the status from “New” to
Approved on our newly created customerSites Application. This is done
with a right-click on the customerSites
application in the detail pane. Select
Approval Status and Approved.
After closing the page builder we’re
back in the Web Studio again, where we
again set the status from “New” to
Approved on the created customersites
page. The last and final step is to add
the page to the existing DefaultPageGroup. This pagegroup is pre-defined
and available to all mobile users when
they connect to the mobile portal.
Testing the application
Unwired Accelerator provides browser access to the mobile device interface.
Just point another browser window to
http://demo.sybase.com:4040/onepag
e/mpindex.jsp.
You won’t have an account when
you’re running Unwired Accelerator for
the first time, but the global.properties.xml property, MB.AutoRegistration,
determines how user accounts are handled when Unwired Accelerator and MBusiness Anywhere are integrated.
If MB.AutoRegistration is set to true,
which is the default, the user automatically joins the M-Business Anywhere
server with the user name and password entered. Feel free to pick whatever you want. I’m using mobile/mobile
as my user/password combination.
After creating the user on the desktop,
use your mobile device (I used my
PocketPC with ActiveSync) to browse to
the mobile portal (using Pocket Internet Explorer with the URL http://<your
machinname>:4040/onepage/mpindex.jsp).
You should be prompted for your
username and password, and after log-
ADD THE APPLICATION TO A PAGE
Action Result
1. Select Pages in the left pane,
select New under Page Manager
Status, and click the New button
to launch Page Builder. Switch to
Full Layout by clicking the layout
button. Click the add button and
you see the search window popping up. Simply click the search
button and choose the customerSites application and click the add
button and click the save button
and give it the name customersites, add the role everybody so
that all people are able to access
the page.
Result
FIGURE 3 | The mobile pages in action
ging in, you will see the default page for
the mobile users. Now choose the customersite page from the dropdown
and, voilà, you’ll see the created page
on your device.
Conclusion
Sybase Unwired Accelerator is an
interesting tool if you want to create
Web applications for mobile devices.
Most of the pages needed can be created by changing a few properties. In this
simple example we used only a few of
the available options. We didn’t touch
the continuous capture feature, which
lets you capture a set of Web pages from
a remote site and define how to extract
the content for display, an impressive
feature. Another feature is the built-in
transaction support, a must for mobile
enterprise applications. Lastly, we didn’t
get into M-Business Anywhere, which
would let us work with a Web-based
mobile application offline. Sybase is
impressive when it comes to mobile
development. Worth getting a demo. ▼
[email protected]
~continued from page 3~
Eating Your Own Dog Food
Blue Marble
If you’re into Geographical Information
Systems, you might want to take a look at
Blue Marble. They just announced a free
evaluation version of their toolkit that “will
allow developers to embed sophisticated
image reprojection and tiling in their applications in a matter of minutes with just a
few function calls.”
Microsoft MVP Program…
Rumors that Microsoft was going to do
8
away with their MVP program (essentially
the equivalent of TeamSybase) have been put
to rest. Actually, their program is just a bit
bigger. There are 30 TeamSybase members,
and there are something like 2,600 Microsoft
MVPs. Part of what was haunting the MVP
program is their recent rapid growth: three
years ago there were only 600 MVPs.
The MVP program was patterned after
TeamSybase (actually TeamPowersoft at the
time). Microsoft hosted a meeting with a
number of TeamPowersoft members shortly
before they launched their program. Can’t
take too much credit though, TeamSybase
was patterned after Borland’s TeamB, which
has been around quite a bit longer. One big
difference with the MVP program is that the
memberships are only good for one year;
you have to keep being reselected. TeamSybase (and TeamB) membership is continuous provided you continue to meet program
requirements. For a glimpse of the early days
of the MVP program, you might check out
the following article on one of the first MVP
summits: www.noveltheory.com/techpapers/mvp.htm.
Resource
• My PBDJ blog: http://bruce.pbdjmagazine.com
TECHNIQUES
About Surrogate and
Natural Keys
WRITTEN BY
MIKE
NICEWARNER
When are they appropriate in a data model?
he purpose of this article is to discuss and describe the terms “Surrogate Key” and “Natural Key,” and
explain when they are appropriate to use
in a data model. Furthermore, the concepts of “Intelligence” and “Generated”
will be applied to both types of keys.
T
The goal is for the reader to understand the plusses and minuses of all
forms of identifying records uniquely
in a database system. The reader is also
challenged to think critically about the
business situation before adopting any
given identification methodology.
Terms Defined
AUTHOR BIO
Mike Nicewarner has
been doing data
modeling since the
early 1990s for a
number of insurance,
manufacturing and
finance companies. He
has taught and written
papers about data
modeling tools and
techniques. When it
comes to modeling
tools, he strives to
improve the state-ofthe-art for everyone
involved.
10
SURROGATE KEY
A surrogate key is a column or
columns that are not defined by business requirements, but are added to a
table simply to identify records
uniquely. For example, a business
might define a set of related attributes
that it wants to keep track of. In that list
there may be a number of items that
could be considered unique (candidate
keys), but none appear to be stable
enough to be the primary identifier for
the set of attributes. The data analyst
might suggest an additional attribute
in the form of an Entity Name plus the
text “Identifier.” For instance, for an
entity called “Survey,” this would be
“Survey Identifier.” There is no business purpose or meaning for this new
attribute, and therefore the resulting
table column would be more resistant
to business changes.
NATURAL KEY
A natural key is a column or
columns that a business chooses to
uniquely identify records. The data
analyst allows them because they are
considered stable enough to be the
primary identifier. For instance, an
existing business process might define
a Product Code that uniquely identi-
fies equipment in a company. By
selecting this as the equipment’s primary key, the business accepts the
resulting database structures more
readily.
INTELLIGENT KEY
An intelligent key derives its name
from the intelligence behind the values
assigned to the columns in the key. For
instance, a Product Code may be a 10character field (defined as CHAR(10) in
the DBMS). This can be mapped as follows: the first two characters are the
business unit, the next two indicate the
month of manufacture, the next three
is a product-type code, the last three is
a sequence number. This specific case
could also be called a concatenated key
since it’s actually a combination of four
separate fields in one single field.
GENERATED KEY
A generated key has no intelligence
to the contents, and is typically
assigned a value by the computer
through some internal mechanism like
a sequential or random number generator or some other method. The point
is that the business doesn’t care about
the value assigned to any given key,
just that a unique value is assigned that
can be referred to by dependent tables.
For example, an Invoice Number might
be defined as a 10-digit number, and
assigned values sequentially, beginning at some starting point and incrementing by one for each new record
added to the Invoice table.
The Keys in Use
In most databases, relationships
between tables are handled in two primary ways, and both can be found.
First is the single-column key. In this
method, each table is assigned a single
primary key column, all foreign keys
are also single-column, and all referential integrity is on pairs of columns.
The second method has the child table
inherit the primary key column(s) from
the parent as part of its own primary
key because it’s a dependent of the parent table. In this case, the key column
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of the child table is not sufficient to
identify the records uniquely, so it
needs both the parent primary key and
the child table primary key.
Single-column primary keys are well
suited to surrogate keys, since the surrogate key has no business meaning
and is stable by itself. They are typically system-generated. Child tables also
have a single unique primary key column. The reference from the child to
the parent is on the single parent column and carried as a mandatory foreign key column in the child. A child of
the child would also have its own
unique primary key column, and
would have a single-column foreign
key to the child table.
Dependent table configurations are
suitable for natural keys. The parent
table has whatever columns are chosen to identify the record uniquely as
its primary key. The child table’s primary key is composed of the parent
primary key plus a column from the
child that makes each record unique.
Since natural keys are defined by the
business, there’s a good chance that at
least one of them will be an intelligent
key.
It’s extremely rare to see just singlecolumn primary keys in a database, or
for all tables to depend on their parents for parts of their primary keys.
Rather, some deference is usually
given to a judicious mix of single- and
multi-column primary keys. For
instance, associative tables typically
have their primary key defined as the
combination of the primary keys of
the parent tables, which may themselves be single-column primary key
tables.
Strengths & Weaknesses
A design that favors single-column
surrogate primary keys will have very
efficient joins between tables, since
most of them will be single-column
joins. Tables will also be narrower than
their natural key cousins, meaning less
deadweight. However, getting from a
deeply
nested
great-great-greatgrandchild table to the ultimate parent
table may take some serious navigation. Read that as complex queries.
Relational database engines are optimized for these kinds of queries, and
the overall reduction in table deadweight tends to offset the complexity
of the queries.
The natural key structure is, simply
enough, more natural for the developer
and the super-user accessing the tables
through their favorite query tool to
deal with. Child tables make sense
12
“My sympathy to
anyone who has
had to make
•
massive changes
throughout a DB2
•
subsystem because
of an intelligent
key that was
anything but”
•
intuitively, since the primary key
columns can be used to discover the
lineage.
Unfortunately, this comes at a fairly
steep price. If any key is intelligent, it’s
going to be almost everywhere, and any
business change will be devastating.
Take the case of a data-type change
because the Product Code described
above has maxed out the three-digit
sequence code. The business started
using letters after it passed 999, and now
even that’s not enough. It wants to make
the last part of the Product Code five digits, increasing the Product Code from
CHAR(10) to CHAR(12). Every table that
uses that Product Code as part of the primary key will have to be structurally
changed. Many databases won’t let you
make that change casually, and typically
require that the data be unloaded, the
table dropped and rebuilt, then the data
reloaded. In large database systems, this
could be a monumental undertaking.
Best Practices
So, what’s the best thing to do? Well,
that depends, of course. There is no
absolute mandate that says there’s only
one way to manage keys. However, to
minimize the impact of future business
changes, there are a few rules of thumb
with a good track record.
• Make every attempt in the initial
design to find an absolutely stable
primary identifier. Press the business
to be honest and say upfront whether
there’s any possibility that the natural
key they recognize will ever change in
•
value or data-type. Be ready with
arguments to support using surrogate keys. They are inherently stable,
perform well in joins, have referential
integrity, and provide simple joins
from table to table.
Establish a maximum limit for nested
dependent tables. One published
guide claims that five levels of dependent tables is a red flag. Re-evaluate
the tables and consider introducing
surrogate keys somewhere along the
line.
If using single-column primary keys,
remember that deeply nested tables
may need a direct foreign key link to
a great-grandparent table. It can provide a shortcut up the chain if the
application and data access tendencies require it. NOTE: This introduces
problems, and violates at least second normal form. However some
denormalization can be tolerated
because database engines aren’t perfect, and complex joins might perform poorly.
Don’t automatically assume that multiple natural keys are bad. Many situations such as Invoice and Invoice
Detail and Order and Order Detail
tables are obvious places to use the
business-understood Line Number as
the Detail table primary key, combined with the parent table primary
key. Trying to force a surrogate key on
the Detail tables would be cumbersome and a relatively poor performer.
As already stated, associative tables
typically use the combined keys of
the parent tables as the primary key.
However, if the associative table is
itself a parent of a lot of other tables,
be ready to come up with a singlecolumn primary key for it.
Disclaimer and Notes
Your experience may vary. If you disagree, great. Please send your feedback
on what I’ve said to the email address
below. I’m always willing to learn and,
heck, I might have left out some important details. My hat’s off to every DBA
who has to maintain a database he
inherited with the kind of Product
Code-from-hell I described. I actually
went through that ordeal in one of the
companies I worked for. My sympathy
to anyone who has had to make massive changes throughout a DB2 subsystem because of an intelligent key that
was anything but. ▼
This article has been reprinted with permission
from www.datamodel.org.
[email protected]
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E V E R Y T H I N G W O R K S B E T T E R W H E N E V E R Y T H I N G W O R K S T O G E T H E R.
Written by Arthur Hefti
o you think, “Why bother using PBDOM?” Well, you can use PDOM
to manipulate elements in an XML document. That means you can
move elements in a document or from one document to another. You
can add elements to a document or delete them from a document. And,
with a little coding, you can import nested XML data into a DataWindow.
S
With the XML capabilities in the DataWindow introduced with
Sybase’s PowerBuilder 9, it’s possible to import and export data very
fast and easily. You might have glanced at the PBDOM definition in
the PowerBuilder help and figured it looked hard to handle but, fear
not, I’ll introduce you to PBDOM and give you some code samples.
Importing & Exporting with DataWindows
Starting with PowerBuilder 9, the DataWindow can import and
export data in XML. This powerful feature lets you exchange large
amounts of data very fast. Importing and exporting is templatebased. You can define several templates for one DataWindow. With
the DataWindow painter, you assign a template for importing and one
for exporting the data. At run-time, it’s possible to change the template using the code. Figure 1 shows the definition of a template in the
DataWindow painter used for export.
Loading data from the EAS Demo DB and saving it with the defined
template generates the XML data in Listing 1.
PDOM Use
PBDOM stands for PowerBuilder Document Object Model. It’s similar to the World Wide Web Consortium’s DOM API and the Java-based
document object model for XML files JDOM. You can find a comparison of these three models in the PowerBuilder Help (PowerBuilder
Extension Reference/PowerBuilder Document Object Model/PBDOM
objects). Technically, PBDOM is implemented as a PBNI (PowerBuilder Native Interface) extension that makes use of the
Apache/Xerces DLL.
14
PBDOM Classes
All PBDOM classes (except PBDOM_Builder and PBDOM_Exception) are inherited from PBDOM_Object.
• PBDOM_Builder is used to create a PBDOM_Document from data
sources like files, strings or DataStores.
• PBDOM_Exception extends the PowerBuilder exception class and
is used for exception handling.
• PBDOM_Object represents any node in an XML node tree and
serves as a base class for the different node types.
• PBDOM_Document is the representation of the XML DOM document. It accesses document-level elements.
• PBDOM_Element represents an XML element and accesses its
attributes, children and text.
• PBDOM_Attribute is the representation of an XML attribute and
accesses its values and namespace information.
• PBDOM_Text represents a DOM text node in a XML document.
• PBDOM_Processinginstruction are the XML document’s processing instructions.
When looking at Listing 1, the saved XML data from the DataWindow, you can see some of the described types. The class
PBDOM_Document references all the data including the XML header.
The PBDOM_Processinginstruction object references the data in the
XML header (e.g., version).
[Processing instructions are used to send instructions to the application that is reading the XML. They begin with "<?" and contain a
target (e.g., "xml-stylesheet") that indicates which application should
be reading the instruction, followed by data for that application and
finally a closing "?>". Technically, the XML Declaration is not a Processing Instruction, although it is often referred to as such and does
has a similar format. – Editor.]
The items CUSTOMERS, CUSTOMER, FIRSTNAME etc. are
PBDOM_Elements. The ID in the CUSTOMER tag is a
PBDOM_Attribute and PBDOM_Text references the values in the tags
like Michaels or Devlin.
A namespace in a document is used to distinguish between elements and attributes with the same name but belonging to different
items. The element CUSTOMER and the element COMPANY could
both have a child element named NAME. References to the element
NAME would be ambiguous without a namespace. The solution with
the prefix, the document, could look like this:
<cust:NAME>Doe<cust:NAME>
<comp:NAME>Sample LLC<comp:NAME>
You will find more details about namespaces on the W3C web site
and many examples and answers on the XML Namespace FAQ at
http://www.rpbourret.com/xml/NamespacesFAQ.htm.
Before you can start working with PBDOM, you have to add
PBDOM100.PBD to the library list. In PowerBuilder’s application
search path the following files should be accessible: PBDOM100.DLL,
PBXerces100.DLL and xerces-c_2_1_0.dll. You have to deploy these
four files with your application. For PowerBuilder 9 choose the
appropriate PBD and DLLs, whereas the Xerces DLL is the same as for
PowerBuilder 10.
Creating an XML Document
An XML document can be created from scratch or from an existing
file, string or DataStore. In Listing 2 the XML output from Listing 1 is
used to generate an XML DOM document. Only minimal error handling is implemented in this listing. The BuildFromFile method from
the PBDOM_Builder class reads and parses the XML Document. The
method returns a reference to the PBDOM_Document.
The next few lines of code lines show some details about the first
level of the document. The method GetContent from the
PDBOM_Document returns an array of objects in the document. In
our sample, the method will return an array of two elements. The first
element is of type PBDOM_Processinginstructions, the second of
type PBDOM_Element and references the element CUSTOMERS.
Calling the method GetRootElement returns the root element of the
document, which is also CUSTOMERS.
To visualize a XML document in PowerBuilder you can use a TreeView. Listing 3 shows a recursive function that takes an array of
PBDOM_Objects and displays it in a TreeView. The function loops
through all elements of the array. Depending on the type of element
different information besides the object name is displayed. In the
case of a PBDOM_Element, the function loops over all the attributes
of this element and creates name/value pairs of each. The name of
the PBDOM_Object plus the display information is added to the TreeView. Should the PBDOM_Object have children, the same function is
called with an array of these children and the handle of the inserted
TreeView item.
array. The function then loops over the attributes and – as soon as the
attribute with the name to search for is found – the value is checked.
When the value matches, the element is returned. If there is no match
and the element has children, the method calls itself passing that element.
[There are W3C standard methods for searching XML documents
known as XPath and XQuery. However, at least when this article was
written, PBDOM does not support XPath or XQuery type operations.
– Editor]
After the appropriate element is found, I add a sales order header
(see Listing 5). At first I create a sales order with CREATE
PBDOM_Element. Then I set the name of this instance to SALESORDER with the method SetName. The SetName method validates the
name (e.g., for spaces in the element name). I then add an attribute
with the name ID and the value 111. For the sales order, I need an
order date and region. I create them, set their name and put the value
into it with SetText. After all these elements are prepared, I put them
together with the method AddContent, which checks the data for
structure (e.g., no loops in a tree) and consistency of namespace to
ensure there is only one root element. To catch the run-time errors, I
put a TRY…CATCH statement around the call.
To demonstrate some additional data manipulation, I also remove
the customer with ID equals 104. The search for that customer is
done using the same method shown in Listing 4. To remove that element the method Detach is used:
lpbdom_Found.Detach()
After the manipulation is done, the XML document can be saved
with the method SaveDocument of the PBDOM_Document. Unfortunately, as of this writing, there was no method to save it to a string or
blob. Instead, you must save the XML to a temporary file and then
read it back into a string or blob, as applicable.
Conclusion
The PDBOM interface is a powerful way to manipulate complex
Manipulating the XML Document
The big advantage with PBDOM is the possibility of manipulating
a single node in a document.
For the following example, I’ll add some information for customer
ID 102.
Using the default EAServer Demo DB, I’ll add an order to the customer. Listing 4 shows how we search for the customer with an ID of
102. The function is recursive and loops through all the elements and
attributes until the element with the required attribute value is
found.
Note that the search is case-sensitive.
Starting with the first element, its content is loaded into an array.
The method loops over the items of this array. If the item is of type
PBDOM_Element the name of it – returned with the method GetName – is compared with the name to search for (CUSTOMER in our
example). When an element with the name to search for is found, the
method GetAttributes loads all the attributes of this element into an
FIGURE 1 | Defining an XML Template
FIGURE 2 | The PBDOM Object Hierarchy
15
XML documents. There are various usages possible. We can use it to
customize style sheets for an application. Another possible use
would be in an EAServer component to manipulate XML before
returning it to the client. This article has provided you with a base to
start from. For additional information, refer to chapter 14 of Application Techniques in the PowerBuilder. In addition, you can also
download other examples at the CodeXchange site of the Sybase
Developer Network. ▼
Listing 1: Saved XML Data
<?xml version="1.0" encoding="UTF-16LE" &
standalone="no"?>
<CUSTOMERS>
<CUSTOMER ID="101">
<FIRSTNAME>Michaels</FIRSTNAME>
<LASTNAME>Devlin</LASTNAME>
<ADDRESS>3114 Pioneer
Avenue</ADDRESS>
<CITY>Rutherford</CITY>
<STATE>NJ</STATE>
<ZIP>07070</ZIP>
<PHONE>2015558966</PHONE>
<COMPANY>The Power Group</COMPANY>
</CUSTOMER>
<CUSTOMER ID="102">
<FIRSTNAME>Beth</FIRSTNAME>
..
</CUSTOMER>
</CUSTOMERS>
Listing 2: Loading a XML Document
PBDOM_Builder
lpbdom_Builder
PBDOM_Document lpbdom_Doc
PBDOM_Object
lpbdom_Obj[]
PBDOM_Element
lpbdom_Root
integer
li_Counter, li_Max
string
ls_Text
// Create PBDOM Builder
lpbdom_Builder = CREATE PBDOM_BUILDER
TRY
// Import File and generate XML
Document
lpbdom_Doc = &
lpbdom_Builder.BuildFromFile(
“XMLOUT.XML” )
CATCH (PBDOM_Exception lpbdom_Except)
// Error Handling goes here,
MessageBox( "PBDOM_Exception", &
lpbdom_Except.GetExceptionCode())
RETURN
END TRY
// Get 1st Level data
lpbdom_Doc.GetContent( lpbdom_Obj )
li_Max = UpperBound( lpbdom_Obj )
FOR li_Counter = 1 TO li_Max
ls_Text = ls_Text + "~r~n" + &
lpbdom_Obj[li_Counter].GetObject
ClassString()+&
": " + lpbdom_Obj[ li_Counter ].Get
Name()
NEXT
lpbdom_Root = lpbdom_Doc.GetRootElement()
ls_Text = ls_Text + "~r~n" + &
lpbdom_Root.GetObjectClassString() + &
": " + lpbdom_Root.GetName()
DESTROY lpbdom_Builder
Listing 3: Display XML Document in a
TreeView
/* Parameters:
pbdom_object apbdom_Obj[]
long al_Parent
*/
PBDOM_Object
lpbdom_Children[]
PBDOM_Attribute
lpbdom_Attr[]
PBDOM_Element
lpbdom_Element
long
ll_Handle
integer
li_Counter, li_Max, li_Attr
Counter, &
li_AttrMax
string
ls_Disp
li_Max = UpperBound(apbdom_Obj)
// Loop through all elements in the array
16
AUTHOR BIO
Arthur Hefti is CEO of CATsoft Development GmbH in Zurich. He has been a PowerBuilder developer for
10 years and has taught dozens of PowerBuilder training classes. He and his team create custom-made
client/server and web software with PowerBuilder and JBoss using XML, Web Services and encryption
quite frequently.
ls_Disp = ""
// Get tag information depeding on type
of entry
CHOOSE CASE &
apbdom_Obj[li_Counter].GetObject
ClassString()
CASE "pbdom_processinginstruction"
ls_Disp = ": " + &
apbdom_Obj[li_Counter].DYNAMIC
GetData()
CASE "pbdom_text"
ls_Disp = ": " + &
apbdom_Obj[li_Counter].DYNAMIC
GetText()
CASE "pbdom_element"
// An element might have
attributes
lpbdom_Element = apbdom_Obj[
li_Counter]
IF lpbdom_Element.HasAttributes()
THEN
lpbdom_Element. GetAttributes
(lpbdom_Attr)
li_AttrMax = UpperBound
(lpbdom_Attr)
// Loop through all attributes
FOR li_AttrCounter = 1 TO
li_AttrMax
ls_Disp = ls_Disp + &
lpbdom_Attr[li_AttrCounter].GetName()+&
"=" + &
lpbdom_Attr[li_AttrCounter].GetText()+ “ “
NEXT
ls_Disp = ": " + ls_Disp
END IF
CASE ELSE
ls_Disp = ": " + &
apbdom_Obj[li_Counter].GetText()
END CHOOSE
// Display name + additional
information
ls_Disp = apbdom_Obj[li_Counter].
GetName()+&
ls_Disp
ll_Handle=tv_1.InsertItemLast(al_
Parent,ls_Disp,0)
// if object has children call the same
function
IF apbdom_Obj[li_Counter].HasChildren()
THEN
apbdom_Obj[li_Counter].GetContent(lpbdom_
Children)
of_BuildTree(lpbdom_Children,ll_
Handle)
tv_1.ExpandItem(ll_Handle)
END IF
NEXT
RETURN
Listing 4: Searching an Element with
Attribute of certain Value
/* Parameters
By reference pbdom_object apbdom_Found
String as_Element, as_Attribute, as_Value
pbdom_object apbdom_Start
*/
boolean
lb_Found
PBDOM_Object
lpbdom_Obj[]
PBDOM_Attribute
lpbdom_Attrib[]
PBDOM_Element
lpbdom_Ele
string
ls_Attribute
long
ll_Counter, ll_Max
integer
li_Counter, li_Max
apbdom_Start.GetContent(lpbdom_Obj)
ll_Max = UpperBound(lpbdom_Obj)
// Loop over all objects
FOR ll_Counter = 1 TO ll_Max
IF lpbdom_Obj[ll_Counter].
GetObjectClassString() &
= "pbdom_element" THEN
[email protected]
lpbdom_Ele = lpbdom_Obj[ll_Counter]
IF lpbdom_Ele.GetName()=as_Element
THEN
// Get Attributes
lpbdom_Ele.GetAttributes(lpbdom_Attrib)
li_Max = UpperBound(lpbdom_Attrib)
// Loop over all Attributes
ls_Attribute = &
lpbdom_Attrib[li_Counter].
GetName()
IF ls_Attribute = as_Attribute
THEN
IF lpbdom_Ele.GetAttributeValue
(ls_Attribute)&
= as_Value THEN
apbdom_Found = lpbdom_Obj
[ll_Counter]
lb_Found = TRUE
EXIT
END IF
END IF
NEXT
END IF
IF NOT lb_Found AND &
lpbdom_Ele.HasChildren() THEN
lb_Found = &
This.of_FindElementWithAttribute
Value( &
apbdom_Found,as_Element,as
_Attribute,&
as_Value,lpbdom_Ele)
END IF
END IF
IF lb_Found THEN
EXIT
END IF
NEXT
RETURN lb_Found
Listing 5: Adding an Element
PBDOM_Element lpbdom_Customer,
lpbdom_Order, &
lpbdom_OrderDate, lpbdom_OrderRegion
TRY
// Create sales order
lpbdom_Order = CREATE PBDOM_Element
lpbdom_Order.SetName( "SALESORDER" )
lpbdom_Order.SetAttribute( "ID", "111" )
// Create order date
lpbdom_OrderDate = CREATE PBDOM_Element
lpbdom_OrderDate.SetName( "ORDERDATE" )
lpbdom_OrderDate.SetText( "2004-12-31" )
// Create order region
lpbdom_OrderRegion = CREATE PBDOM_
Element
lpbdom_OrderRegion.SetName(
"ORDERREGION" )
lpbdom_OrderRegion.SetText(
"Switzerland" )
// Add elements to sales order
lpbdom_Order.AddContent( lpbdom_
OrderDate )
lpbdom_Order.AddContent( lpbdom_
OrderRegion )
// Add sales order to customer
lpbdom_Customer.AddContent(
lpbdom_Order )
CATCH (PBDOM_Exception lpbdom_Except2)
// Error Handling goes here,
MessageBox( "PBDOM_Exception", &
lpbdom_Except2.GetExceptionCode())
RETURN
END TRY
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volume11
volume12
issue
issue10
2
BOOK EXCERPT
Part Art, Part Science
Part 1
WRITTEN BY JIM
esigning and implementing an n-tier or Internet application is
a complex task, and issues resulting from errors in the runtime
configuration or the application code itself are practically
inevitable. Problem analysis and troubleshooting are part art, part
science. Therefore, although the techniques discussed here can be
helpful, the sheer diversity of client and server environments precludes a single recipe for resolving all issues.
D
We’ll focus on problems that involve PowerBuilder that occur from
the point of connectivity all the way through an EAServer component’s lifecycle, and close with a troubleshooting checklist of potential resolutions to some of the more common error situations.
Client and Server Environment
One of the first techniques for validating both the client and
EAServer environments involves checking the versions and locations
of the PowerBuilder executable modules (DLLs on Microsoft Windows platforms) and Java classes that are loaded at runtime. In terms
of PowerBuilder clients and components, Sybase recommends that
the version of the PowerBuilder Virtual Machine (VM) on the client
machine match that used by EAServer. This is required rather than
recommended when using proprietary techniques such as the blob
format used in DataWindow synchronization (for example, the getFullState and setFullState methods).
Client Requirements
Client requirements for PowerBuilder applications that access
EAServer are no different than those for client/server applications.
Specific requirements are detailed in the “Application Techniques”
18
PBDJ volume12 issue2
O’NEIL
manual accompanying the PowerBuilder product, and include the
PowerBuilder VM (PBVM90.DLL), the DataWindow engine
(PBDWE90.DLL), database interface libraries and the EAServer client
ORB implementation (LIBJCC.DLL).
NOTE: Client applications built using the initial release of PowerBuilder 9.0 require that one additional DLL, LIBJSYBHEAP.DLL, be
deployed. Beginning with the 9.0.1 maintenance release, this DLL is
no longer required because its functionality has been subsumed by
PBVM90.DLL.
All of the PowerBuilder DLLs used for a given client application
must be of the same build.
Although LIBJCC.DLL ships with PowerBuilder, it’s actually an
EAServer module and, as such, isn’t stamped with a specific version
number. Because the implementation is backward-compatible, your
client application should use the LIBJCC.DLL shipped with the most
recent version of EAServer to which it may connect. Several tools are
available to determine what DLLs have actually been loaded by your
client application. The Sysinternals web site (www.sysinternals.com)
has many useful diagnostic tools, including listdlls and ProcessExplorer, that can be used for this. You can even get a list of modules
loaded through the About dialog box in Microsoft Word.
Server Requirements
All versions of EAServer have a serverstart.bat file (or serverstart.sh file on Unix plat¬forms) that contains the core of the environment setup and the actual command to launch the server executable image (jagsrv). In EAServer 4.0 and later, a setenv and
optional user_setenv command file accompany the serverstart
script. When the serverstart script is invoked, it invokes the other
two scripts to set site-specific environment requirements complementing those required by the core EAServer product. The primary
environment variables used by EAServer 4.0 and later are shown in
Table 1.
For most installations, neither the serverstart nor the setenv script
requires modification. A user_setenv script may be required, though,
to supply additional libraries or classes. For example, Informix JDBC
connection caches require that the IBM Informix JDBC driver classes
be located on the CLASSPATH, and Oracle OCI caches on a Windows
2000 server require that the Oracle client software be accessible via
the PATH variable.
CLASSPATH
The CLASSPATH that is established for EAServer can be viewed
directly from the server properties of Jaguar Manager. Keep in mind,
however, that EAServer also uses custom class loaders during its execution, so the absence of a required class on the system CLASSPATH
doesn’t necessarily mean that failure is imminent. However, the presence of a class on the system CLASSPATH can interfere with an identical class loaded by a custom class loader resulting in a Java ClassCastException or ClassNotFoundException. The remedy is to ensure
that all classes required by a component are loaded via custom class
loaders. You do this by including such classes in the java.classes
property of the associated application, web application, servlet,
package, component or even the server itself.
EAServer offers two tracing options to help diagnose class loader
errors.
• Setting the com.sybase.jaguar.server.jvm.verbose property to true
causes the location from which each class is loaded to be recorded in the EAServer log file.
• Setting com.sybase.jaguar.server.classloader.debug to true also
records the class loader used for each class.
Listing 1 is an excerpt from the EAServer log where both these
properties have been set. The trace lines prefaced with JCL: result
from the classloader.debug option, while the others originate with
the jvm.verbose setting. This particular example shows the sequence
used to instantiate the Java Connection Manager ( JCM) service upon
server startup.
BOOTCLASSPATH
Environment Variable Description
JAGUAR
Root directory of EAServer
installation
JAGUAR_HOST_NAME Machine name for default
listeners
JAGUAR_JDKnn
Root JDK directory
(nn = 12, 13, 14)
Root directory of the JDK
JDK_LATEST
being used to launch the
server; assumes the
value of one of the
JAGUAR_JDKnn variables
CLASSPATH
Search path for Java classes
required for server operations
Where Set
setenv
setenv
setenv
serverstart
serverstart for core
classes
user_setenv for sitespecific requirements
classes
classes.
BOOTCLASSPATH
Search path for Java classes
to be bootstrapped before
the built-in JRE classes
PATH (Intel)
LD_LIBRARY_PATH
(Solaris) LIBPATH (AIX)
SHLIB_PATH (HP-UX)
Search path for executable
images (DLLs, shared objects.
and so on), including the
EAServer libraries, and the
JDK libraries
Search path for native functions user_setenv
(in DLLs or shared objects)
invoked by Java classes
BOOTLIBRARYPATH
TABLE 1 | EAServer environment variables
Operating System
Microsoft Windows
(NT, 2000, and XP)
Solaris
HP-UX
AIX
Utility
Command
listdlls (from www. listdlls -r jagsrv.exe
sysinternals.com)
pldd
/usr/proc/bin/pldd pid, where pid is
the process ID of jagsrv determined
by running ps -ef | grep jagsrv
shl_get()
Requires implementing an EAServer
component that invokes shl_get()
genld
genld
The BOOTCLASSPATH is used with JDK 1.2 and later so the system
class loader can load classes before it loads the core Java classes provided in rt.jar. This is required whenever alternative implementations of classes located in rt.jar need to be used. For instance, in
EAServer 4, the EAServer ORB class is org.omg.CORBA.ORB and is
located in easclient.jar. Sun’s rt.jar distribution, however, also
includes this class. To ensure that EAServer uses the Sybase implementation, the serverstart script puts easclient.jar on the BOOTCLASSPATH ahead of rt.jar.
Other classes that need to access classes on the BOOTCLASSPATH
may also need to be added to the BOOTCLASSPATH. A common
example is third-party JDBC drivers used by EAServer connection
caches such as the Oracle Thin JDBC driver. If you include the driver
classes (such as %ORACLE_HOME%/jdbc/lib/classes12.zip) in the
CLASSPATH but not in the BOOTCLASSPATH, you will encounter a
ClassNotFoundException due to class loader conflicts.
platform and functionality.
The value of the Microsoft Windows PATH variable (and its Unix
analogs) used by EAServer can be ascertained via the operating system commands and utilities shown in Table 2. These utilities are particularly useful in ensuring that the correct versions of the PowerBuilder libraries are loaded at runtime.
The listdlls utility has an advantage over the Unix commands
because each DLL version is reported as part of the output. On Unix
platforms, you need to extract the version number from each specific object file using the strings command. For instance, the following
command on HP-UX reports the version of the PowerBuilder VM
implemented by the libpbvm80x.sl file:
PATH
strings libpbvm80x.sl | grep -i “^Version [0-9]”
At a minimum, PowerBuilder 9.0 components running in EAServer
require that the PBVM90 and PBJAG90 modules be available on the
operating system path established for the EAServer process. Generally, most components make use of DataStores and one or more database connections; therefore, the PBDWE module and one or more
database interfaces (PBJDB, PBODB, PBSYJ, PBO90 and so on) are
also needed. The “Application Techniques” manual accompanying
PowerBuilder provides specifics on the binary images required by
TABLE 2 | Commands and utilities for viewing modules loaded by a process
JVMType Switch
When starting EAServer or installing it as a service on a Microsoft
Windows system, the -jvmtype switch can specify that the client,
server or classic Java VM be used (assuming that the JDK version and
operating system support is use). Historically, the Java server VM has
had a reputation for being less stable than the client VM, and
although it’s tuned for application server performance, you may
19
Error Code Representative ErrText
50
Unsupported driver name
57
This connection object is not
connected to a server
92
Required property is missing
Potential Remedy
Set the driver property of the
Connection object to jaguar.
This error can have a number of
causes, as explained further in
this section.
Set the location or userid prop
erty of the Connection object.
TABLE 3 | Error codes resulting from a failed connection attempt
want to use the default client VM if you encounter specific stability
issues. Generally, stability is more of a factor in older releases of the
Java VM and is characterized by rather severe Java VM abort messages
appearing in the EAServer log.
Considerations When Running as a Service
When running EAServer as a service on Microsoft Windows operating systems, the key environment settings are drawn from the registry hive at \\HKEY_LOCAL_MACHINE\ SYSTEM\CurrentControlSet\Services\service-name\Parameters, where service-name is
the name of the EAServer instance provided on the serverstart install command line.
The settings for PATH, CLASSPATH and BOOTCLASSPATH are
stored in the registry when the service is installed. When the service
is actually started, the current values of these environment variables
are appended to the values that were stored in the registry when the
service was created. Because the EAServer process itself sets these
environment variables, a minimal environment that includes the
%JAGUAR%/dll directory in the system PATH must exist for the service to start.
Also note that when installing the service, the CLASSPATH is
extended to include each JAR or ZIP file located in the
%JAGUAR%/java/lib directory. If you start the server as a service,
only the JARs and ZIPs present in that directory when the service was
installed are added to the CLASSPATH. In contrast, when starting the
server via the serverstart batch file, the JARs and ZIPs present in that
directory at the moment the server is started are dynamically added
to the CLASSPATH.
Manager) or an EAServer custom authentication service to verify
user credentials. When using one of these techniques, multiple failed
requests will lock you out of the server because it has interpreted
those requests as a possible attack. Note: The excerpt from the
EAServer log (see Listing 2) where the IP address of the client
attempting access is recorded can be useful in identifying the failed
client or the source of an attempted break-in.
Obviously, if the client fails to connect with the server, the EAServer log won’t contain any error information, so the absence of information itself can be a clue to the cause. As a first step in diagnosing
such cases, ensure that the location property of the Connection
object has the following format:
protocol://server:port
Here, the protocol is either iiop or iiops. Next, match this value to
an entry at the beginning of the server log similar to this:
Dec 23 21:22:08 2002: Listener # 6: Jaguar_iiop: Active: yes
Protocol: ‘IIOP’: ‘phoenix’,9000 Security Profile: ‘*NONE*’
If the Active attribute is set to no, the listener is not operational, as
the following EAServer log entry demonstrates:
Dec 23 21:33:19 2002: SRVLIB Message: 16240/10/0: Net-Library
routine
?net_listen(phoenix 9000) failed in srv__start_listeners Network
error: status = 23 - Net-Lib protocol driver call to register a
listener failed
The most common causes for this behavior are that another server
instance is already running or that some other application has
already claimed use of that port. To verify, use the netstat command
to determine what ports are in use. Listing 3 shows some output of
the netstat command executed on a Solaris machine. Here the presence of ports 8080 and 9000 (both default EAServer ports) in a LISTEN state likely means that an EAServer instance is already running
on that machine.
Tracing Client Connectivity Requests
Connecting to EAServer
Some of the most common and easiest issues to overcome involve
connectivity from a PowerBuilder application or another client to
EAServer. Connectivity issues may occur because of configuration
issues in the client environment, failures on the server side or even
issues involving firewalls and network address translation.
In some cases, the EAServer log file alone might provide little
insight into why you failed to connect to the server. In these situations, you might have to resort to tracing the underlying network
protocol traffic. Using EAServer or Sybase and even third-party tools
there are ways to capture packets to and from EAServer in any of the
three supported communication protocols: IIOP, HTTP, and TDS.
Diagnosing Failed Connections
IIOP Requests
The Connection object is the usual mechanism for establishing a
client connection to EAServer from PowerBuilder. When the connection to server fails, the ConnectToServer method returns one of the
error codes shown in Table 3. That information, along with the contents of the ErrText property of the Connection object, often reveals
the root cause of the failure.
The error code 57 can pop up in a number of scenarios such as a
reference to a nonexistent server, an incorrect communications protocol or an invalid user ID or password. By default, a client attempts
to connect five times with a delay of two seconds between tries;
therefore, an error 57 immediately returned to the client generally
indicates that it found the server but that there was a problem validating the user’s credentials. If the failure results from a timeout, it’s
usually because the location property doesn’t specify a valid operating EAServer. In both cases, an investigation of the EAServer log via
Jaguar Manager or a text editor is in order.
By default, EAServer doesn’t validate any user except for the special administrative user, jagadmin. You need to use operating system
authentication (an EAServer server property configurable via Jaguar
To turn on IIOP tracing from a PowerBuilder client, populate the
options property of the Connection object with the ORBLogIIOP and
ORBLogFile parameters, as demonstrated next. For the ORBLogFile
attribute, make sure that a full path is given and enclosed in quotation marks:
20
ln_connect.options = “ORBLogIIOP=’true’,ORBLogFile=’c:\orb.log’”
Listings 4 and 5 contain excerpts of an IIOP client trace indicating
a failed session initialization. The IIOP putMessage in Listing 4 shows
the request to create a session for user jagadmin using the password
badpwd. The response (see Listing 5) is in the form of an IIOP
getMessage packet that contains a NO_PERMISSION exception
because the wrong password was given.
Detailed analysis of IIOP packets is really beyond our scope here;
however, the chapter entitled “General Inter-ORB Protocol” in The
Common Object Request Broker: Architecture and Specification
(available from www.omg.org) can be used to help interpret these
traces.
You can also enable IIOP tracing on EAServer itself by setting the
com.sybase.jaguar.server.log.iiop server property to true. Many
internal workings of EAServer are handled via inter-component calls
using IIOP — not to mention the fact that a server may be handling
many clients — so IIOP logging causes the EAServer log to grow
quickly. You can reduce the size of the log somewhat by setting the
com.sybase.jaguar.server.log.iiop.ac property to true, which defers
the tracing until the server actually begins accepting requests from
clients.
HTTP Requests
When using PowerBuilder client applications, the primary mode of
communicating with EAServer is via IIOP. PowerBuilder’s GetURL
and PostURL functions, however, offer a mechanism to access
EAServer servlets and JSPs via the HTTP protocol (HTTPS is not supported here). In such a scenario, PowerBuilder accesses EAServer as
a web server, so you can diagnose connectivity issues as you would
when trying to access any web site from a browser client such as
Internet Explorer. The error and return codes are those defined by the
World Wide Web Consortium (W3C) in the HTTP specification available from www.w3c.org.
Three log files associated with EAServer running as a web server
can aid in diagnosing problems with HTTP client requests.
1. The HTTPRequest log provides a one-line summary of every URL
accessed, the IP address of the requesting client, the HTTP return
code and the number of bytes of data returned. This log also contains entries for failed requests such as the ubiquitous 404 Page
Not Found.
The default format for this file is the Common Log Format as
defined by the W3C. Extended log file format (as shown in Listing
6) can also be enabled by setting the
hostaddr
date
time
reqline
status
length
cookie
referer
user-agent
method
uri-stem
http_version
host
port
TABLE 4 | Extended log file format options
its capabilities when compared to IIOP connectivity options, PowerBuilder’s SYC database driver can access components in EAServer via
a TDS port and the technique known as Methods as Stored Procedure
(MASP).
The Ribo utility shipped with the jConnect for JDBC driver and
available by free download from the Sybase web site is a convenient
tool for tracing TDS traffic. We will discuss Ribo in more detail in the
upcoming section on diagnosing database access issues. It’s more
likely that you will use the tool to investigate the interaction of
EAServer connection caches with Sybase databases and gateways.
Instantiating Components
Most component instantiation failures happen because of coding
errors or problems in the server environment. PowerBuilder clients
(or other EAServer components making inter-component calls) usually initiate component instantiation via the Lookup or CreateInstance functions. Both methods are available on the Connection
object for client access and the TransactionServer object for intercomponent calls. The lower-level JaguarORB object can also be used
to access EAServer and instantiate components via the base CosNaming techniques.
Establishing Server Connectivity
“Connectivity issues can arise
because of configuration issues
in the client environment, failures
on the server side or issues
involving firewalls and network
address translation”
com.sybase.jaguar.server.http.elffenable server property to true in
Jaguar Manager.
The additional property com.sybase.jaguar.server.http.elffitems
lets you specify exactly which items are included in the extended
log file format and in what order they appear. The options include
those in Table 4 where the default value for this property is
hostaddr,date,time,reqline,status,length, cookie,referer.
2. The HTTPServlet log includes information about servlet and JSP
execution. This log proves valuable in determining the cause of
HTTP 500 Internal Server Errors because it records Java class
loading errors and JSP compilation failures. You can also set the
com.sybase.jaguar.server.servlet.trace property to true to provide
additional information about servlet initialization and execution.
3. The HTTPError log records HTTP server failures such as socket
errors when writing a response to the client’s HTTP port.
TDS Requests
Tabular Data Stream (TDS) is Sybase’s proprietary protocol for
communicating between Open Client and Open Server applications,
such as Adaptive Server Enterprise. Although it’s rather restrictive in
22
Error 57 can also occur as a return code from the CreateInstance or
Lookup functions on the Connection object and usually indicates a
coding error or failure to handle errors returned from the ConnectToServer method. Because error 57 means there’s no server connection, the EAServer log file won’t contain any information to help diagnose the failure.
When using the JaguarORB object in PowerBuilder to connect to
the server, you first create proxies for various EAServer packages such
as SessionManager and Factory. As a rule, rather than returning error
codes, these methods throw exceptions when there are failures, so
they should be issued in the context of TRY-CATCH blocks in your
PowerScript client code.
Locating Components
Locating a component on EAServer before instantiating it involves
two distinct steps. First, verify that a component with the requested
name exists on one or more EAServers cataloged by the targeted
naming server. If the component is found, the second step is to confirm that the component instance found does indeed implement the
desired interface. The failure of either step results in EAServer reporting one of the following two exceptions:
• omg.org/CosNaming/NamingContext/NotFound
• omg.org/CORBA/OBJECT_NOT_EXIST
Now let’s look a little closer at the processing involved here to get a
better understanding of common points of failure.
Lookup
The first step toward locating a component is verifying that the
named component is accessible to one of the naming server(s) specified in the Connection object’s location property or in the ORBNameServiceURL property supplied when initializing the JaguarORB
object.
When using COSNaming via the JaguarORB object, the component
name is explicitly provided via the NameComponent structure. When
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FIGURE 1 | Client error message occurring from a failed component
lookup
using the PowerBuilder Connection object, the component name is
taken directly from the Lookup function or from the CreateInstance
function, if the optional component name argument is provided.
When you use the one-argument form of the CreateInstance function, PowerBuilder constructs the component name based on the
default package name (specified in the application property of the
Connection object), followed by a / character and then the variable
type of the proxy argument. Although this sounds convenient, we
recommend that you always use the two-argument form of CreateInstance for the following reasons:
• You must always remember to change the application property of
the Connection object when calling components in different
packages. If the application property of the Connection object
isn’t specified, the Connection object will report error code 92 as
shown in Table 17.3.
• If you elected to generate proxies that are prefaced by the package name, the instantiation will fail because the variable type
seen by PowerBuilder (that is, the proxy name) won’t match the
actual component’s name.
Whatever the source of the component name, the naming server
checks its list of bound objects (created at startup or refresh) to see if
any of the object names match. Although the standard naming convention is package/component, if the com.sybase.jaguar.component.bind.naming property is explicitly set, its value is the name by
which the server recognizes the component. The component’s bound
name doesn’t have to resemble the actual package or component
name as installed on the server.
So let’s assume at this point that the requested component was
located on at least one server and continue on to the next step.
Narrow
When using the CreateInstance method, the component is narrowed to a SessionManager::Factory interface only. It assumes that
the corresponding proxy used in the client application includes valid
interface methods implemented by the component. Any impending
failures in this regard are not made manifest until a method is
invoked on the component.
When using the Lookup method, the interface specified must be
the home interface of the requested EJB; otherwise, the actual lookup
will succeed, but the attempt to narrow the component to that interface will fail. The client will still show an error 57 code, which may be
puzzling because the component name itself could be correct.
When using the JaguarORB and the Narrow function of the PowerBuilder CORBAObj object, the interface must also be specified. A
failed Narrow method at runtime may produce no error; however, it
will result in aberrant application behavior. A good programming
practice is to always verify the implementation of an interface via the
is_a function on CORBAObj before attempting to narrow the object
reference to that interface.
Common Causes of Lookup Issues
EAServer doesn’t consider a lookup failure to be an error, so no
information is recorded in the EAServer log for this step. Although
you may see errors in the log when using the CreateInstance function, they are actually recorded when an attempt is made to instantiate the component on the target server (which we’ll discuss in the
next session). Some of the common causes of failure to locate components are:
24
• The package containing the desired component isn’t installed on
the specific EAServer being targeted (or on any of the member
servers in the case of a clustered environment). It’s not enough
for the package to be included in the EAServer repository; it must
be installed in each server instance where it may be needed.
• The package or component name was misspelled as in Figure
17.1. The package and component names aren’t case-sensitive in
this context.
• The bound name of the component is something other than the
default package/component format, which can be verified by
examining the component’s bind.naming property. This property
isn’t case-sensitive either.
• When using Lookup or CosNaming (via the JaguarORB object)
directly, the desired interface name isn’t found, perhaps because
it’s misspelled. In this case, the name of the interface is case-sensitive.
Instantiating Components
A component isn’t instantiated when the CreateInstance or
Lookup is issued. It happens when the first method call is requested
for that instance. The lookup step previously described results in a
list of EAServer profiles (a server and port combination) where the
requested component can be instantiated. In a clustered environment, this list likely includes multiple EAServers. The client ORB
always tries to instantiate a component on the first server in the profile list, assuming that the profile list is already in an order that
appropriately reflects the load-balancing technique selected for that
cluster. If the instantiation fails because of a communication error
(for example, the server has gone down), the request is retried transparently on the next server in the profile list returned by the naming
server.
Because the list of profiles is returned to the client from the naming server, there’s a change in context in the interpretation of the
server locations included in those profiles. This change in context
can cause instantiation failures in two common scenarios:
• When a standalone EAServer or a server in a cluster has an active
localhost listener (such as the loopback address of 127.0.0.1), that
listener is returned to the client application that requests a component along with the list of profiles. If the client ORB attempts to
use that localhost profile to instantiate the component, the
attempt will fail because localhost is now the client machine, not
the EAServer machine hosting the component. In a production
environment, there’s no need for localhost listeners.
• When accessing EAServer through a firewall, the server addresses
in the profile list returned to the client may be unreachable. In an
internal network, the private IP addresses (namely 10.x.x.x,
172.16.x.x and 192.180.x.x as designated by the Internet Assigned
Numbers Authority) are often used to identify machines running
on the corporate intranet. So the EAServer naming servers in that
environment use those internal addresses when creating the list
of profiles that indicate where a requested component can be
instantiated.
If that list of profiles is forwarded to service a request from an
EAServer client outside the firewall, the instantiation will fail because
these private Internet addresses aren’t reachable from the client.
When using firewalls that do network-address translation from publicly accessible IP addresses to private IP addresses, you must configure your clients’ host file to do reverse-address translation or use the
ORBProxyHost and ORBProxyPort parameters when initializing the
client ORB.
Assuming that the server on which the component is to be instantiated is indeed reachable, let’s look at how EAServer loads the component implementation for a PowerBuilder component. Understanding the four main steps of this process, as outlined here, can help
identify the source of the errors if the instantiation fails:
1. EAServer determines the implementation model via the compo-
nent’s com.sybase.jaguar.server.type property. For PowerBuilder components,
this value is always pb.
2. EAServer next determines the PowerBuilder version in which the component
was implemented by examining the com.sybase.jaguar.component.pb.version
property. If the property isn’t specified, the component is assumed to have
been built using PowerBuilder 7.
3. If it hasn’t been loaded already, EAServer initializes the PowerBuilder VM.
Each component instance is allocated a unique session in the one instance of
the PowerBuilder VM hosted by the EAServer process.
4. Finally, the PowerBuilder VM determines what PBDs to load for the component by consulting the com.sybase.jaguar.component.pb.cookie and
com.sybase.jaguar.component.pb.librarylist properties. The library list can
contain two kinds of entries:
• PBDs or PBLs prefaced by a $ are loaded from an EAServer repository subdirectory of that component named Cn, where n is the value of the
pb.cookie property (and increases for each deployment from PowerBuilder).
• PBDs or PBLs with explicit or relative paths not prefaced by the $ are located according to normal pathing rules for the host operating system. To use
this approach, you must manually change the librarylist property in Jaguar
Manager; furthermore, if you redeploy the component from PowerBuilder
later, your changes will be overwritten.
When these steps fail, it’s usually a problem in the EAServer configuration. The
error in the EAServer log will provide insight into the actual cause of the failure.
The client application, on the other hand, will experience the generic
CORBA::OBJECT_NOT_EXIST or CORBA::TRANSACTION_ROLLEDBACK exceptions.
Invoking Component Methods
Assuming that everything has been error-free so far, the next step is the actual
method invocation. Although the success of the method execution depends
largely on whether the developer correctly implemented it, there are at least two
circumstances in which a method invocation might fail before it even gets into
the PowerBuilder component’s code.
Failed invocations can occur in the development cycle when obsolete proxy
objects are used. Whenever you modify the component interface on EAServer,
you must be sure to regenerate the proxies for those interfaces on PowerBuilder.
The PowerBuilder proxies are merely remote wrappers for the component’s functionality that the client application currently thinks is available. Any attempt to
call a method that doesn’t exist (or no longer exists) results in a CORBA::TRANSACTION_ ROLLEDBACK or CORBA::BAD_OPERATION exception.
In a production environment, an instantiation can fail when valid component references become invalid because, say, the EAServer on which the instance was hosted has failed. If you have configured the component for failover (by setting the
com.sybase.jaguar.component.auto.failover property) and the component is marked
as being automatically demarcated/ deactivated (the com.sybase.jaguar.component.tx_vote property is false), successive attempts to access the component automatically fail over to the other EAServer instances returned in the original list of profiles derived from the lookup request. If failover isn’t configured or there are no
remaining servers in the cluster that can host the requested component, a
CORBA::OBJECT_NOT_EXIST or CORBA::COMM_FAILURE exception will occur
when the client invokes the method on that component. ▼
This article is based on PowerBuilder 9 Internet and Distributed Application Development
by various authors (ISBN 0672324997), published by Sams Publishing.
AUTHOR BIO
Jim O’Neil is a principal technical support engineer at Sybase, Inc. He has been with Sybase for six years, concentrating on resolving customer issues with Sybase products such as PowerBuilder, EAServer and PowerJ. Prior to Sybase,
Jim spent about 10 years working as a software engineer for two defense contracting firms.
[email protected]
25
LISTING 1 EAServer Log Showing Class Loader Diagnostics
Dec 23 21:22:12 2002: JCL:JCL <4127408>: custom=
Dec 23 21:22:12 2002: JCL:setName <4127408>: Name changing
from 4127408 to Jaguar/JCM
Dec 23 21:22:12 2002: JCL:setDirs <Jaguar/JCM>:
_dirs=[Ljava.lang.String;@3c5982
Dec 23 21:22:12 2002: JCL:displayArray <Jaguar/JCM>: strs
= [Ljava.lang.String;@3c5982
Dec 23 21:22:12 2002: JCL:displayArray <Jaguar/JCM>:
strs.length = 3
strs[0] = C:\Program Files\Sybase\EAServer/java/classes/
strs[1] = C:\Program Files\Sybase\EAServer/html/classes/
strs[2] = C:\Program Files\Sybase\EAServer/java/lib/
Dec 23 21:22:12 2002: JCL:setCustomList <Jaguar/JCM>:
custom=
Dec 23 21:22:12 2002: JCL:loadClass <Jaguar/JCM>:
name=com.sybase.jaguar.jcm.JCM
name=com.sybase.jaguar.jcm.JCM, resolve=false
Dec 23 21:22:12 2002: JCL:loadClass <Jaguar/JCM>: ?class
DefName=com.sybase.jaguar.jcm.JCM,
name=com.sybase.jaguar.jcm.JCM, resolve=false
Dec 23 21:22:12 2002: JCL:loadClass <Jaguar/JCM>: ?class
DefName=com.sybase.jaguar.jcm.JCM,
name=com.sybase.jaguar.jcm.JCM, resolve=false, trySystem
ClassLoader=true
Dec 23 21:22:12 2002: JCL:loadClass <Jaguar/JCM>: Try from
our local cache
Dec 23 21:22:12 2002: JCL:inCustomList <Jaguar/JCM>:
name=com.sybase.jaguar.jcm.JCM
Dec 23 21:22:12 2002: JCL:inCustomList <Jaguar/JCM>:
len=0, rets=false
incustom=false
Dec 23 21:22:12 2002: JCL:loadClass <Jaguar/JCM>: try the
system class loader
Dec 23 21:22:12 2002: [Loaded com.sybase.jaguar.jcm.JCM
Dec 23 21:22:12 2002: from C:\Program Files\Sybase\
EAServer\java\lib\easserver.jar
Dec 23 21:22:12 2002: ]
LISTING 2 EAServer Log Showing a Lockout Situation
Dec 23 19: 03:10 2002: NO_PERMISSION: user jagadmin
(possible attack from ?65.57.230.61)
Dec 23 19: 03:10 2002: SystemException: NO_PERMISSION
(Manager/createSession [email protected])
Dec 23 19: 03:13 2002: NO_PERMISSION: user jagadmin
(account locked for 600 seconds)
Dec 23 19: 03:13 2002: SystemException: NO_PERMISSION
(Manager/createSession [email protected])
LISTING 3 Netstat Output Showing Active Ports
phoenix% netstat -a -P tcp TCP
Local Address
Recv-Q State
phoenix.58616
ESTABLISHED
phoenix.8080
phoenix.8081
phoenix.9000
phoenix.9001
phoenix.telnet
ESTABLISHED
LISTING 5 IIOP Response Packet Sent to Client Application
IIOP putMessage Hexadecimal [padding] (interpretation)
ISO 8859-1 encoding
getOctet < 47 (71) G
getOctet < 49 (73) I
getOctet < 4F (79) O
getOctet < 50 (80) P
getOctet < 01 (1)
.
getOctet < 01 (1)
.
getOctet < 01 (1)
.
getOctet < 01 (1)
.
getULong < 3C000000 (60) <...
getMessage
| GIOP version = 1.1
| flags = 1 (‘<’ little endian)
| message type = 1 (Reply)
| message size = 60 (after 12 byte header)
getReply | service context:
getRequest
| service context length:
getULong < 00000000 (0) ....
getReply | request id:
getULong < 00000000 (0) ....
getReply | reply status:
getULong < 02000000 (2) ....
getULong < 24000000 (36) $...
getString < 49444C3A6F6D672E6F72672F434F5242412F4E
4F5F5045524D495353494F4E3A312E3000IDL:omg.org/CORBA/
NO _PERMISSION:1.0.
getULong < 00000000 (0) ....
getULong < 01000000 (1) ....
Remote Address Swind Send-Q Rwind
LISTING 6 HTTPRequest Log in Extended Log File Format
hpsupp.6000
32768
0
8760 0
0
0
LISTEN
0
0
*.*
*.*
0
0
0
0
LISTEN
*.*
0
0
0
0
LISTEN
0 LISTEN
0
0
0
*.*
otter.44460 24820 0
8760 0
LISTING 4 IIOP Request Packet Issued from Client Application
IIOP putMessage Hexadecimal [padding] (interpretation)
ISO 8859-1 encoding
putOctet < 47 (71) G
putOctet < 49 (73) I
putOctet < 4F (79) O
putOctet < 50 (80) P
.
putOctet < 01 (1)
.
putOctet < 01 (1)
putBoolean
< 01 (TRUE) .
.
putOctet < 00 (0)
26
putULong < 00000000 (0) ....
| GIOP version = 1.1
putMessage
| flags = 1 (‘<’ little endian)
| message type = 0 (Request)
putRequest
| service context length:
putULong < 00000000 (0) ....
| request id:
putRequest
putULong < 00000000 (0) ....
| response expected:
putRequest
putBoolean
< 01 (TRUE) .
| reserved:
putRequest
.
putOctet < 00 (0)
putOctet < 00 (0)
.
.
putOctet < 00 (0)
putRequest
| object key:
putULong < 02000000 (2) ....
putOctets < 4D00 M.
putRequest
| operation:
putULong < 00000E000000 [2] (14) ......
putString < 63726561746553657373696F6E00 createSession.
putRequest
| requesting principal:
putULong < 000000000000 [2] (0) ......
putRequest
| request body:
putULong < 09000000 (9) ....
putString < 6A616761646D696E00 jagadmin.
putULong < 00000007000000 [3] (7) .......
badpwd.
putString < 62616470776400
endMessage
| message size = 71 (after 12 byte header)
#Version: 1.0
#Date: 2002-12-21 18:50:40
#Fields: s-ip date time cs-request cs-status cs-bytes
cs(Cookie) cs(Referer)
199.95.51.242 2002-12-21 18:50:40 “GET /ir/CtsServlet.html
HTTP/1.1” 200 318 - “
http://porkchop:8080/ir/index.html”
199.95.51.242 2002-12-21 18:50:43 “GET
/ir/CtsServlet__ServletService.html HTTP/
1.1” 200 436 - “http://porkchop:8080/ir/CtsServlet.html”
199.95.51.242 2002-12-21 18:50:49 “GET /ir/
CosTransactions.html HTTP/1.1” 200 43
6 - “http://porkchop:8080/ir/index.html”
199.95.51.242 2002-12-21 18:52:14 “GET /webapp/index.html
HTTP/1.1” 404 369 - 199.95.51.242 2002-12-21 18:55:58 “GET /customer/index.jsp
HTTP/1.1” 404 361 -
DOWNLOAD THE CODE!
DROPDOWN FILTERING
Dynamic Web Page Content
WRITTEN BY
RAHUL JAIN
Without refreshing the page
ropdown filtering is one of the
most requested features in web
applications and one of the seemingly more difficult tasks. There are
many ways to provide dropdown filtering including retrieving all possible values and filtering on the client side with
JavaScript as well as making round trips
to the server to reload the page with a
filtered dropdown.
D
AUTHOR BIO
Rahul Jain is a
distributed systems
architect with Cynergy
Systems (www.cynergysystems.com). He has
more than eight years
of experience building
web, distributed
and client-server
applications using
PowerBuilder, EAServer
and EAF.
28
Here we will explore a more sophisticated approach that uses the XMLHttpRequest DOM object to retrieve
the data from the server using XML and
repopulate the dropdown without
refreshing the page. Our main purpose
is to show you how to use the XMLHttpRequest object. It’s more useful
than just for dropdown filtering. It can,
for instance, be used to validate the
client-side data, get data dynamically
and call Web Services.
What is the XMLHttpRequest object?
The XMLHttpRequest document is a
client-side object that can process
HTTP calls with any valid URL.
Although it’s called the XMLHttpRequest object, it’s not limited to being
used with XML, it can request or send
any type of HTTP-compliant data using
standard HTTP calls.
What we basically do with this object
is send data to the server side and get
content back, all in the background.
The data returned could be a simple
string like “true” or a more complex
XML document. The return could also
be binary content, but that could be a
little difficult to handle in JavaScript.
Microsoft first implemented the
XMLHttpRequest object in Internet
Explorer 5 for Windows as an ActiveX
object. Firefox and Safari also come
with a native version of the object.
1. Create the object.
2. Make a request to the server page.
3. [optional] Check for errors.
4. [optional] Process the data returned.
In Firefox and Safari you use this
code instead:
Take a look at the very simple script
below:
A call to the “open” function in line 2
opens the http request and specifies
the information. The method signature is:
1 var xmlHttp = ActiveXObject
("Microsoft.XMLHTTP ");
2 xmlHttp.open (“GET”, “customerlist.jsp”, false);
3 xmlHttp.send ();
4 var returnValue = xmlHttp.
responseText;
The code on line 1 is creating the
object. In Internet Explorer, you can
create the object using a script depending on the version of MSXML installed.
new ActiveXObject ("Msxml2.XMLHTTP")
or
new ActiveXObject ("Microsoft.XML HTTP")
new XMLHttpRequest()
Open (“method”, “URL”[, asyncFlag[,
“username”[, “password”]]])
In this method we are telling the
object the page name (URL), what
method to use (GET/POST) and
whether we want the call to be synchronous or asynchronous, true by
default (more on this argument in a
minute). We can optionally supply the
username and password to be used for
the call.
The call to the “send” method in line
3 sends the http request to the server.
Line 4 captures the data sent back from
the server.
Using the XMLHttpRequest
object in JavaScript
The script for using the object is simple. The following steps are involved:
PBDJ ADVERTISER INDEX
ADVERTISER
URL
PHONE
PAGE
Active Endpoints, Inc.
www.active-endpoints.com
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2
Amyuni Technologies
www.amyuni.com
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33
Assande
www.assande.com
ClearNova
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770-442-8324
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E.crane
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36
iAnywhere
www.ianywhere.com
800-801-2069
35
IT Solutions Guide
www.sys-con.com/IT
201-802-3020
23
PowerBuilder Developer's Journal
www.sys-con.com/pbdj
201-802-3026
27
Sybase
http://eshop.sybase.com/eshop
877-230-6771
11
Sybase
www.sybase.com/pbextension
877-230-6771
13
Sybase
www.sybase.com/powerbuilder
877-230-6771
5, 17
Sybase
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7
9
Advertiser is fully responsible for all financial liability and terms of the contract executed by their
agents or agencies who are acting on behalf of the advertiser. This index is provided as an additional service to our readers. The publisher does not assume any liability for errors or omissions.
29
Synchronous and
Asynchronous Calls
Method
Description
abort()
Stops the current request
getAllResponseHeaders()
Returns complete set of headers (labels and
values) as a string
getResponseHeader("headerLabel")
Returns the string value of a single header label
open("method", "URL"[, asyncFlag[,
"userName"[, "password"]]])
Assigns destination URL, method, and other
optional attributes of a pending request
send(content)
Transmits the request, optionally with postable
string or DOM object data
setRequestHeader("label", "value")
Assigns a label/value pair to the header to be
sent with a request
1 var xmlHttp = ActiveXObject
("Microsoft.XMLHTTP ");
2 xmlHttp.onreadystatechange =
processCustomerList;
3 xmlHttp.open (“GET”,
“customerlist.jsp”);
4 xmlHttp.send ();
Line 2 in script above tells the object
what to do when the call is completed.
Now the question becomes how to
make sure the call was successfully
completed. Take a look at the script
below to get an idea.
1 function processCustomerList () {
2
if (xmlHttp.readyState == 4) {
3
if (xmlHttp.status == 200) {
4
// Process the list
5
}else{
6
alert (“Problem occurred
retrieving the Customer
List.\n” +
xmlHttp.statusText);
7
}
8
}10 }
9
PowerBuilder Makes It Easy
With DataWindow’s XML feature, all
we really need to do is send the XML
content back. So the same DW that
you’ve been using for dropdowns can
now be used with various templates
and sent back to the client. To be able to
filter dropdowns dynamically, we will
need a JSP to return the XML to the
client side with the data and display
values. So, to achieve this, create a JSP
30
Common XMLHttpRequest Object Methods
An important though optional third
parameter to the open method is a
Boolean value that controls whether
the upcoming transaction should be
handled asynchronously. The default
behavior (true) is to act asynchronously, which means that script processing
carries on immediately after the send
method is invoked, without waiting for
a response.
If you set this value to false, however,
the script waits for the request to be
sent and for a response to arrive from
the server. While it might seem like a
good idea to wait for a response before
continuing processing, you run the risk
of your script hanging if a network or
server problem prevents the completion of the transaction.
It’s safer to send asynchronously and
design your code around the onreadystatechange event for the request
object. The script below is an example
of how to make an asynchronous call.
Common XMLHttpRequest Object Properties
Property
Description
onreadystatechange
Event handler for an event that fires at every
state change
readyState
Object status integer:
0 = uninitialized
1 = loading
2 = loaded
3 = interactive
4 = complete
responseText
String version of data returned from server
process
responseXML
DOM-compatible document object of data
returned from server process
status
Numeric code returned by server, such as 404
for "Not Found" or 200 for "OK"
statusText
String message accompanying the status code
TABLE 1 | XMLHttpRequest Reference
and call the PB component that would
generate the XML from the DW. On the
client side we will need to parse this
XML and repopulate the dropdown.
The responseXML property of the
object can be used to get the XML that
is returned by the server.
To see a basic live example, please
see this page: http://demos.cynerg y s y s t e m s. c o m / e a f e x a m p l e s / c u s tomerorder.jsp. This example is built
using PB 10 abd EAF. As you can see, on
this page we have a DW with two
columns, Customer and Order. Order
DDDW is filtered on change of Customer. In itemchanged event of the DW,
we grab the customer ID and pass it to
the order JSP via XMLHttpRequest and
get the orders XML back, which is then
parsed and populated in the order
dropdown. ▼
References
You might find following links useful
for further reading:
• Using the XML HTTP Request object:
http://jibbering.com/2002/4/httpre-
quest.html
• Dynamic HTML and XML: The XMLHttpRequest Object: http://developer.apple.com/internet/webcontent/x
mlhttpreq.html
• How to Submit Form Data by Using
XMLHTTP or ServerXMLHTTP Object:
http://support.microsoft.com/default
.aspx?scid=KB;ENUS;Q290591&ID=KB;EN-US;Q290591
• Get dynamic Web content with
HTTPRequest: A refreshing approach
to page refreshes: www106.ibm.com/developerworks/web/li
brary/wa-httpget/
You also might want to read about
how Google uses XMLHttpRequest
object in its Gmail and Google Suggest
applications. This link might help:
• Chris Justus – Server Side Guy: “Google
Suggest Dissected...”: http://serversideguy.blogspot.com/2004/12/googl
e-suggest-dissected.html
[email protected]
Power Puzzle
1
2
3
4
5
6
7
8
9
10
11
12
13
15
14
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Created with EclipseCrossword — www.eclipsecrossword.com
Across––––––––––––––––––––––––-------------------------------------3. An _______ key is called this because there is
intelligence behind the values assigned to the
columns in the key. (Nicewarner)
4. Search path for Java classes to be bootstrapped
before the built-in JRE classes (O’Neill)
7. A ________ in a document is used to distinguish
between elements and attributes with the same
name but belonging to different items. (Hefti)
8. Define the organization of applications with
more than one element, where applications are
located, background HTML code, and so on.
(Hamboeck)
11. By default, a client attempts to connect five
times with a delay of two seconds between
attempts; therefore, a 57 error immediately
returned to the client generally indicates that
the server was located but that there was a
problem _______the user’s credentials. (O’Neill)
12. PowerBuilder’s GetURL and PostURL functions,
however, offer a mechanism to access EAServer
servlets and JSPs via the ____ protocol. (O’Neill)
14. Technically, PBDOM is implemented as PBNI
(PowerBuilder ______ Interface) extension that
makes use of the Apache/Xerces DLL. (Hefti)
16. The one [new SOAP standard] of particular interest to PowerBuilder developers will be XOP
(XML-binary _____ Packaging), a standard means
of transmitting binary data via XML. (Armstrong)
18. The _______ property of the [XMLHTTPREQUEST] object can be used to get the XML that
is returned by the server. (Jain)
20. Here we create user-defined hierarchies of content for display in an application. (Hamboeck)
25. The ____________ log provides a one-line summary of every URL accessed, the IP address of
32
Answers available online at www.sys-con.com/powerbuilderpuzzle
the requesting client, the HTTP return code, and
the number of bytes of data returned. (O’Neill)
26. ______ Data Stream (TDS) is Sybase’s proprietary protocol for communicating between
Open Client and Open Server applications, such
as Adaptive Server Enterprise. (O’Neill)
27. A ____ key is a column or columns that are chosen by the business to uniquely identify records,
and are allowed by the data analyst because
they are considered to be stable enough to
become the primary identifier. (O’Neill)
29. As stated already, __________ tables typically use
the combined keys of the parent tables as the
primary key. (Nicewarner)
30. [When using the XMLHTTPREQUEST] It is safer
to send asynchronously and design your code
around the ________ event for the request
object. (Jain)
31. The remedy for such errors [Java ClassCastException or ClassNotFoundException] is to
ensure that all classes required by a component
are loaded via _____ class loaders. (O’Neill)
Down––––––––––––––––––––––––-------------------------------------1. A _______ key has no intelligence to the contents, and is typically assigned a value by the
computer through some internal mechanism.
(Nicewarner)
2. If you start the server as a service, only the JARs
and ZIPs present in that directory when the service was installed are added to the __________.
(O’Neill)
5. In EAServer 4.0 and later, a _______ and optional
user_setenv command file accompany the
serverstart script. (O’Neill)
6. The method ____ from the PBDOM_ Builder
class reads and parses the XML Document.
9. Search path for native functions (in DLLs or
shared objects) invoked by Java classes (O’Neill)
10. They are needed, for example, if we want to
write a portlet’s content to a file, an e-mail message, or a database table. (Hamboeck)
13. Many internal workings of EAServer are handled
via ________________ calls using IIOP-not to
mention that a server may be handling many
clients-so IIOP logging causes the EAServer log
to grow very quickly. (O’Neill)
15. The default behavior [of the XMLHTTPREQUEST Open method] (true) is to act ___, which
means that script processing carries on immediately after the send method is invoked. (Jain)
17. However some ______ may be tolerated because
database engines aren’t perfect, and the complex joins might perform poorly. (Nicewarner)
19. The ______________ document is a client side
object that can process HTTP calls with any
valid URL (Jain)
21. A __________ key is a column or columns that
are not defined by business requirements, but
are added to a table simply to uniquely identify
records. (Nicewarner)
22. PBDOM means PowerBuilder _________ Object
Model (Hefti)
23. Establish a maximum limit for the number of
_______ dependent tables. (Nicewarner)
24. ____________ table configurations are suited for
natural keys. (Nicewarner)
28. The most common cause of this behavior [NetLib protocol driver error] is that another server
instance is already running or that some other
application has already claimed use of that ____.
(O’Neill)
PowerBuilder News
All things of interest to the PB community
BY BRUCE ARMSTRONG
[email protected]
Third-Party Tools
PBmiqui announced the availability of several code samples, including a wrapper for
the FreeImage DLL using
PBNI, a multiselect DDLB, and
Pbintelli, an expanded IntelliSense add-in for the PowerBuilder IDE, currently in beta.
www.miqui.it/
DataWindow.Net
DataWindow.Net is a nominee
in the 2004 Best .NET Products
of 2005 awards in the libraries
and controls category.
www.sys-con.com/dotnet/readerschoice2004
iAnywhere
2/14 – iAnywhere Solutions, a
subsidiary of Sybase,
announced that SQL Anywhere
Studio powers innovative
health care applications developed by MedicWare,
MediNotes Corporation,
Microlog, and Microsys Computing, Inc. SQL Anywhere
Studio from iAnywhere helps
vendors deliver cost-effective
and quality health care solutions that enable organizations of any size to deliver
timely access to critical
patient information, streamline business processes, and
reduce administrative costs.
announced that Relavis Corporation, a world leader in
customer relationship management (CRM) solutions, has
selected the iAnywhere Pylon
34
Application Server to power its
soon-to-be released eSales
Mobile application. Using
Pylon Application Server,
eSales Mobile will enable sales
people to access key company
information, track leads,
update customer profiles and
manage accounts through
handheld devices.
announced that it was awarded two MobileTrax 2005 Mobility Awards. The company’s
Answers Anywhere product
was pocked as a winner in the
“Software” category, while its
April 2004 acquisition of XcelleNet also won in the “Mergers
and Acquisitions” category.
iAnywhere was the only software company to win in more
than one category for the wellknown annual Mobility
Awards.
subsidiary of Sybase, launched
the latest version of its AvantGo service, delivering superior
features for managing and
viewing mobile Internet content offline or online, anywhere at anytime. Enhanced
capabilities allow for improved
wireless synchronization, easier on-device web-channel
management and expanded
support for AvantGo users,
resulting in a more robust
online and offline user experience.
Sybase Corporate
01/15 – Sybase reported total
license revenues increased 7%
for the fourth quarter ended
December 31, 2004 compared
with the same quarter the previous year. Total revenues for
the quarter increased 4% to
$218.6 million from $210.7
million for the
fourth quarter of 2003.
Adaptive Server Enterprise
2/15 – Sybase announced at
LinuxWorld Conference &
Expo the general availability of
its relational database management system (RDBMS),
Sybase Adaptive Server Enterprise (ASE) for Linux on IBM’s
eServer OpenPower systems
with complete support and
consulting services from
Sybase and IBM to support
mission-critical applications.
Sybase ASE for IBM’s eServer
OpenPower systems offers the
lowest total cost of ownership
(TCO) of any enterprise database on Linux. Sybase and
IBM will coordinate worldwide
sales, marketing, and services
responsibilities for the Linux
platform, with a strong focus
on offering solutions that meet
the demanding requirements
of the financial services sector.
Recognized as a Linux database total cost of ownership
(TCO) leader by The Standish
Group, Sybase ASE was the
first RDBMS ported to the
Linux OS, and has garnered
several prestigious awards,
including LinuxWorld Magazine’s Readers’ Choice Award
for “Best Linux Database.”
2/15 – Sybase announced that
its enterprise class relational
database Sybase ASE 12.5.2
has attained a security certification of level 4 (EAL4) from
the International Common
Criteria for Information Technology Security Evaluation,
making it the most recent
database offering in the industry to achieve this level of certification. This certification
level, the highest achieved by
general-purpose software, is
evidence of Sybase ASE’s
impressive security features
such as SSL-protected com-
munications and row-based
access controls.
The Common Criteria Certification is required by the
United States Government
before any IT products can be
considered for purchase by
government offices, departments, and other federally
funded organizations. In addition, Common Criteria is an
internationally recognized
security evaluation required
by numerous central governments worldwide for any of
their departments interested
in procuring commercially
available products. Common
Criteria certification also
assures businesses of a standard measure of the security
design of their computing
products.
01/06 – Sybase announced
that its enterprise-class relational database management
system, Sybase Adaptive Server Enterprise (ASE) for Linux,
won Open Source World’s Editor’s Choice Award for the
“Best Linux Database.” Sybase
ASE won the publication’s
“Best SME Linux Package
Award” with ASE for Linux and
Turbolinux 7 Server at the
same event in 2003. Through
its outstanding product performance and after-sale services, Sybase ASE for Linux has
gained widespread recognition.
Events
TechWave 2005
August 21-25
Caesar’s Palace
Las Vegas, Nevada
www.sybase.com/techwave
Forget the wires.
We know
the ropes.
Wondering how to get your Wi-Fi projects off the ground? We can show
you how. We’re iAnywhere Solutions,
the leading provider of solutions for
the unwired enterprise.
Emerging wireless technologies such
as Wi-Fi now enable businesses to
deliver a desktop computing experience to mobile workers. We have
more than a decade of experience
delivering "always available" access to
corporate data and applications –
keeping your mobile workers productive when they don’t have a wireless
connection and providing information
security and synchronization services
when they enter a wireless LAN or hot
spot.
More than ten thousand companies
and one thousand partners worldwide
rely on mobile technology from
iAnywhere Solutions.
Let us show you the ropes to get your
Wi-Fi solutions off the ground quickly. Call 1-800-801-2069 or visit
www.ianywhere.com.
Copyright 2003. iAnywhere Solutions, Inc. All rights reserved. iAnywhere is a trademark of Sybase, Inc. or its subsidiaries.
All other trademarks are the property of their respective owners.
www.ianywhere.com

PBDJ 11-5Y - SYS

Transcription

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