95-733 Internet Technologies Lecture 1: Introduction 1 Master of Information System

Transcription

95-733 Internet Technologies
Lecture 1: Introduction
Master of Information System
Management
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Course Web Site
• http://www.andrew.cmu.edu/~mm6
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Prerequisites
• The ability to program in Java
• Enthusiasm for programming
• Interested in web technologies
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Specific Technologies
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Netbeans and Glassfish
JavaScript, Servlets and Java Server Pages
XML (various languages)
AJAX
Mashups
Freebase
Ruby
Frameworks – Ruby on Rails
Grammars - DTD’s, XSDL, JSON Schema
XML Transformation - XSLT
Semantic Web – OWL, RDF, Protégé, Jena
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Structure of the Course
• Lectures / class participation
• Demonstrations
• Homework (programming)
• Midterm
• Final examination
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Readings
• Readings from the required text are assigned for each
lecture -- read them in advance
• Readings from the web also assigned
• For this week read “Programming the World Wide Web”,
7th ed. Chapters 1, 2 and 3. Especially chapter 3 on
CSS.
• For next week read “Programming the World Wide
Web”, 7th ed. chapters 4, 5 and 10.
• Chapters 4 and 5 are on JavaScript
• Chapter 10 covers AJAX.
• Read the article by Philip McCarthy of IBM on AJAX
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Grading
• Homework/Programming (3-5) 50%
• One of the homework problems is designed by
the student. A presentation and demonstration
is required. See me soon about your topic.
• For the student designed homework, small
groups are permitted. Each student presents
for the same number of minutes.
• Midterm 10%
• Final Exam 40%
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Some Suggested Topics For
Student Assigned Homework
• Explore one of the many XML languages
in more detail than we do in class.
• Discuss and demonstrate an HTML5
element (audio, video, time, canvas).
• HTML5 document structure
• HTML5 Local storage.
• Flash, PhoneGap, GWT, Jquery, etc…
• SOFEA
• Many other options exist. See the
schedule
for Technologies
projects from previous
95-733 Internet
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terms.. Management
Rich Internet Applications
• The traditional web employed thin
clients.
• In RIA, the browser is extended by
downloaded code.
• With AJAX, the downloaded code
interacts with the server
asynchronously. The client does not
block.
• This makes for a more responsive user
experience.
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RIA Using Ajax
Asynchronous Java Script and XML
• Why bother?
- Everyone loves the browser but
communication with the server is
coarse-grained. A full page reload
interrupts the interaction flow.
• Example Applications: (Web 2.0)
- Google Maps runs in a browser but
behaves like an application.
- Flikr photo sharing, Google Maps,
Blackboard, etc.. use AJAX.
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AJAX
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Typically uses JavaScript or VBScript on the client side.
The server side might be in any language, e.g., PHP, ASP.NET, or
Java.
Any XML document or text may be returned to the caller. Simple text,
JavaScript Object Notation (JSON) or XML is common.
Client-side Javascript libraries like Dojo or Prototype or Jquery may be
used.
Frameworks (RoR, JSF, etc.,) support Ajax.
Normally, requests may only go back to the originating
server.
However, mashups (combining diverse site output) may still be
constructed by having the originating server make calls to other
servers.
Client side mashups may also be built with a dynamic <script> tag.
Ajax is important to mobile phones. JSON service access is easy
See www.openajax.org
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Before We Start
• A servlet is Java code that runs on
the server when an HTTP request
arrives.
• A Java Server Page (JSP) is
XHTML+ Java and is compiled to a
servlet.
• JavaScript is not Java and runs in
the browser.
• XHTML is one of many XML
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languages
Management
This is a UML
sequence diagram.
This shows a
typical AJAX
round trip.
A solid arrowhead
represents a
synchronous
call.
A stick
arrowhead
represents an
asynchronous
signal.
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Typical Ajax(1)
1. Javascript and HTML is delivered to the
browser.
2. The JavaScript code is pointed to by
a <script> tag.
3. The HTML defines a button that
calls a function.
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Typical Ajax(2)
4. Within the function (which may be
passed a URL with GET data) a
browser dependent request object is
created with a URL (and, perhaps,
GET data).
5. A handler is defined.
6. The request object is told about the
handler.
7. The request object is told to send a
post or get request asynchronously.
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Typical Ajax(3)
8. If POST is used, the send method is
called on the request object
with the POST data.
9. The handler executes on various state
changes in the request object.
10.The handler accesses the server
response by asking the request
object first for its state (and if it's
ready with no errors) its response.
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Typical Ajax(4)
11. The response may be text,
or XML or JSON.
12. The handler performs some
action on the browser. This
action may alter the HTML's
DOM and change what the
browser displays.
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The XMLHttpRequest Object as
Described by W3C
• The XMLHttpRequest interface can be used
by scripts to programmatically connect to their
originating server via HTTP.
• Implements an interface exposed by a
scripting engine.
• Supports any text format (not only
XML).
• Supports HTTP and HTTPS.
• The term “Request” should be broadly
defined to include Request and
Response.
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W3C Example 1
Some simple JavaScript code to do
something with data from
an XML document fetched over
the network:
function test(data) {
// taking care of data
}
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function handler() {
if(this.readyState == 4 &&
this.status == 200) {
// so far so good
if(this.responseXML != null &&
this.responseXML.getElementById('test').firstChild.data)
// success!
test(this.responseXML.getElementById('test').firstChild.data);
else
test(null);
} else if (this.readyState == 4 && this.status != 200) {
// fetched the wrong page or network error...
test(null);
}
}
var client = new XMLHttpRequest();
client.onreadystatechange = handler;
client.open("GET", "test.xml");
client.send();Master of Information System
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Management
W3C Example 2
If you just want to ping the server with a message you could
do something like:
function ping(message) {
client.open("POST", "/ping");
client.send(message);
}
We are not establishing a callback
handler. We are not interested in a response.
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W3C Example 3
Or, if you want to check the status of a document on the server,
you can make a head request.
function fetchStatus(address) {
client.onreadystatechange = function() {
if(this.readyState == 4)
returnStatus(this.status);
}
client.open("HEAD", address);
client.send();
}
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State and State Change
The state of the object. The readyState attribute must be
one of the following values:
0 Uninitialized The initial value.
1 Open The open() method has been successfully called.
2 Sent The user agent successfully acknowledged the
request.
3 Receiving Immediately before receiving the message
body (if any). All HTTP headers have been received.
4 Loaded The data transfer has been completed.
When readyState changes value a readystatechange
event is to be dispatched on the XMLHttpRequest object.
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Typical Interaction
post
JavaScript function
XML
XMLHTTPRequest
handler
HTML Button
Management
- Executed on
state change.
- this.responseXML
points to the root
of the XML
-write HTML to 24
HTML DOM
A Complete Example From IBM
Demonstrations:
See article by Philip McCarthy on Ajax at:
http://www.ibm.com/developerworks/library/j-ajax1/
Eclipse workspace mm6/95-733
Visit http://localhost:8080/AjaxProject/index.jsp
Netbeans workspace mm6/95-733/AjaxUsingNetbeans
ACoolAjaxShoppingCart and
ACoolAjaxShoppingCartImproved
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Main Features of Index.jsp (1)
This page needs access to these imported Java packages.
<%@ page import="java.util.*" %>
<%@ page import="developerworks.ajax.store.*"%>
The store package contains
Item.java, Catalog.java and Cart.java
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The header holds pointers to script code to be included in the
page and then executed by the browser.
<script type="text/javascript"
language="javascript" src="ajax1.js">
</script>
<script type="text/javascript"
language="javascript" src="cart.js">
</script>
This is not constrained by the same origin
policy!
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The table body tag encloses table rows that are generated on
the server. This is Java (part of JSP) and is not JavaScript.
<tbody>
<%
for (Iterator<Item> I =
new Catalog().getAllItems().iterator();
I.hasNext() ; ) {
Item item = I.next();
%>
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The addToCart call is a call on JavaScript.

<tr>
<td><%= item.getName() %></td>
<td><%= item.getDescription() %></td>
<td><%= item.getFormattedPrice() %></td>
<td>
<button onclick="addToCart('<%= item.getCode() %>')">
Add to Cart
</button>
</td>
</tr>
<% } %>
</tbody>
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The <ul> and <span> tags each have a unique identifier.
These identifier will be used by the event handler.
<div style=”…”>
<h2>Cart Contents</h2>
<ul id="contents"></ul>
Total cost:
<span id="total">$0.00</span>
</div>
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Main Features of Item.java
package developerworks.ajax.store;
import java.math.BigDecimal;
Getter and setters on
code, name,description
and price.
public class Item {
private String code;
private String name;
private String description;
private int price;
public Item(String code,String name,String description,int price) {
this.code=code;
this.name=name;
this.description=description;
this.price=price;
}
public String getCode() {
return code;
}
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Main Features of Catalog.java(1)
import java.util.*;
public class Catalog {
private static Map<String,Item> items;
static {
items = new HashMap<String,Item>();
items.put("hat001",new Item("hat001",
"Hat","Stylish bowler hat (SALE!)",
1999));
:
}
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Main Features of Catalog.java(2)
public Collection<Item> getAllItems() {
return items.values();
}
public boolean containsItem(String itemCode)
{
return items.containsKey(itemCode);
}
public Item getItem(String itemCode) {
return items.get(itemCode);
}
}
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Main Features of Cart.java(1)
public class Cart {
private HashMap<Item,Integer> contents;
public Cart() {
contents = new HashMap<Item,Integer>();
}
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public void addItem(String itemCode) {
Catalog catalog = new Catalog();
if (catalog.containsItem(itemCode)) {
Item item = catalog.getItem(itemCode);
int newQuantity = 1;
if (contents.containsKey(item)) {
Integer currentQuantity = contents.get(item);
newQuantity += currentQuantity.intValue();
}
contents.put(item, new Integer(newQuantity));
}
}
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public String toXml() {
StringBuffer xml = new StringBuffer();
xml.append("<?xml version=\"1.0\"?>\n");
xml.append("<cart generated=\""+
System.currentTimeMillis()+
"\" total=\""+getCartTotal()+"\">\n");
for (Iterator<Item> I = contents.keySet().iterator() ; I.hasNext() ; ) {
Item item = I.next();
int itemQuantity = contents.get(item).intValue();
xml.append("<item code=\""+item.getCode()+"\">\n");
xml.append("<name>");
:
xml.append("</cart>\n");
return xml.toString();
}
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Main Features of
CartServlet.java(1)
private Cart getCartFromSession(HttpServletRequest req)
{
HttpSession session = req.getSession(true);
Cart cart = (Cart)session.getAttribute("cart");
if (cart == null) {
cart = new Cart();
session.setAttribute("cart", cart);
}
return cart;
}
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Main Features of
CartServlet.java(2)
public void doPost(HttpServletRequest req,
HttpServletResponse res)
throws java.io.IOException {
Enumeration headers = req.getHeaderNames();
while (headers.hasMoreElements()) {
String header =(String) headers.nextElement();
System.out.println(header+":
"+req.getHeader(header));
}
Cart cart = getCartFromSession(req);
String action = req.getParameter("action");
String item = req.getParameter("item");
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Main Features of
CartServlet.java(3)
if ((action != null)&&(item != null)) {
if ("add".equals(action)) {
cart.addItem(item);
} else if ()…..
}
String cartXml = cart.toXml();
res.setContentType("text/xml");
res.getWriter().write(cartXml);
}
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Main Features Axis1.js (1)
/*
* Returns an new XMLHttpRequest object, or false if the browser
* doesn't support it
*/
function newXMLHttpRequest() {
var xmlreq = false;
// Create XMLHttpRequest object in non-Microsoft browsers
if (window.XMLHttpRequest) {
xmlreq = new XMLHttpRequest();
}
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else if (window.ActiveXObject) {
try {
// Try to create XMLHttpRequest in later versions of Internet Explorer
xmlreq = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e1) { // Failed to create required ActiveXObject
try {
// Try version supported by older versions of Internet Explorer
xmlreq = new ActiveXObject("Microsoft.XMLHTTP");
} catch (e2) {
// Unable to create an XMLHttpRequest by any means
xmlreq = false;
}
}
}
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/* Returns a function that waits for the specified
XMLHttpRequest to complete, then passes it XML response
to the given handler function.
req - The XMLHttpRequest whose state is changing
responseXmlHandler - Function to pass the XML response to
*/
function getReadyStateHandler(req, responseXmlHandler) {
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// Return an anonymous function that listens to the
// XMLHttpRequest instance
return function () {
// If the request's status is "complete"
if (req.readyState == 4) {
// Check that we received a successful response from the server
if (req.status == 200) {
// Pass the XML payload of the response to the handler
// function.
responseXmlHandler(req.responseXML);
} else {
// An HTTP problem has occurred
alert("HTTP error "+req.status+": "+req.statusText);
}}}}
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Main Features Cart.js (1)
// Timestamp of cart that page was last updated with
var lastCartUpdate = 0;
// Adds the specified item to the shopping cart, via Ajax call
// itemCode - product code of the item to add
Establish handler
and pack up and
send the request.
function addToCart(itemCode) {
var req = newXMLHttpRequest();
req.onreadystatechange = getReadyStateHandler(req, updateCart);
req.open("POST", "cart.do", true);
req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
req.send("action=add&item="+itemCode);
}
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/*
* Update shopping-cart area of page to reflect contents of cart
* described in XML document.
*/
function updateCart(cartXML) {
var cart = cartXML.getElementsByTagName("cart")[0];
var generated = cart.getAttribute("generated");
if (generated > lastCartUpdate) {
lastCartUpdate = generated;
var contents = document.getElementById("contents");
contents.innerHTML = "";
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var items = cart.getElementsByTagName("item");
for (var I = 0 ; I < items.length ; I++) {
var item = items[I];
var name = item.getElementsByTagName("name")[0].firstChild.nodeValue;
var quantity = item.getElementsByTagName("quantity")[0].firstChild.nodeValue;
var listItem = document.createElement("li");
listItem.appendChild(document.createTextNode(name+" x "+quantity));
contents.appendChild(listItem);
}
}
document.getElementById("total").innerHTML = cart.getAttribute("total");
}
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Shopping Cart Interaction
post
addToCart(itemCode)
XML
XMLHTTPRequest
HTML Button
UpdateCart
reads XML
writes HTML
Management
Anonymous handler
- Executed on
state change.
- req.responseXML
points to the root
of the XML
- calls updateCart
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The handler is reading data with the following format:
<?xml version="1.0"?>
<cart generated="1200367057873" total="$19.99">
<item code="str001">
<name>String</name>
<quantity>1</quantity>
</item>
</cart>
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Another Example From
Sebesta Chapter 10
A form is required to collect name, address, zip, city, and state.
The zip code entry causes an asynchronous call on a servlet
to automatically complete the city and state fields.
The asynchronous call is made when the user blurs (or moves
away from) the zip code field.
This demo is in the Netbeans project
mm6/www/95-733/AjaxUsingNetbeans/SebestaAjaxExample.
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Index.jsp Main Features
<tr>
<td> Zip Code: </td>
<td> <input type = "text" name="zip" size = "10"
Locations
onblur = "getPlace(this.value)" />
written to by
</td>
ajax handler
</tr>
<tr>
<td> City </td>
<td> <input type = "text" name="city" id= "city" size = "30" /> </td>
</tr>
<tr>
<td> State </td>
<td> <input type = "text" name="state" id="state" size = "30" /></td>
</tr>
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Javascript Main Features
function getPlace(zip) {
var xhr;
if(window.XMLHttpRequest)
xhr = new XMLHttpRequest();
else
xhr = ActiveXObject("Microsoft.XMLHTTP");
xhr.onreadystatechange = function() {
if(xhr.readyState == 4) {
var result = xhr.responseText;
var place = result.split(', ');
document.getElementById("city").value = place[0];
document.getElementById("state").value = place[1];
}
}
xhr.open("GET", "ZipToCityStateServlet?zip="+zip,true);
xhr.send(null);
}
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Two Servlets - One for
AJAX
protected void processRequest(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try {
// Return simple text to Ajax request
if(request.getParameter("zip").equals("15216"))
out.println("Pittsburgh, PA");
else
out.println("New York, NY");
} finally {
out.close();
}
}
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Another For the Form
out.println("<h2>Name: " + request.getParameter("name") + "</h2>");
out.println("<h2>Street: " + request.getParameter("street") + "</h2>");
out.println("<h2>Zip: " + request.getParameter("zip") + "</h2>");
out.println("<h2>City: " + request.getParameter("city") + "</h2>");
out.println("<h2>State: " + request.getParameter("state") + "</h2>");
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XML Or JSON ? (1)
<Person firstName="John" lastName="Smith">
<Address>
<streetAddress>21 2nd Street</streetAddress>
<city>New York</city>
<state>NY</state>
<postalCode>10021</postalCode>
</Address>
<phoneNumber type="home"> 212 555-1234 </phoneNumber>
<phoneNumber type="fax"> 646 555-4567 </phoneNumber>
</Person>
Management
From Wikipedia.org
54
XML Or JSON ? (2)
{
}
"firstName": "John", "lastName": "Smith",
"address":
{ "streetAddress": "21 2nd Street",
"city": "New York", "state": "NY",
"postalCode": "10021"
},
"phoneNumbers":
[ { "type": "home", "number": "212 555-1234" },
{ "type": "fax", "number": "646 555-4567" } ]
If this text is in the variable coolText, then we can create a
JavaScript object with the line of code:
var x = eval("(" + coolText + ")");
And access the data with x.phoneNumbers[0].
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From Wikipedia.org 55
Which To Use?
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Which To Use?
JSON has some advantages over XML:
JSON messages are smaller and therefore faster.
Very little parsing is required.
JSON is simpler and simple is good.
XML has some advantages over JSON:
If the document is to be integrated more or less intact, XML is
better. With JSON, you would need to construct the tags.
XSLT can be used to transform a response into an appropriate
format.
XML Signature and XML Encryption not available for JSON.
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Some Popular Toolkits
Any survey of all of the toolkits would quickly be obsolete.
•
jQuery supports Ajax
• ASP.NET AJAX
This is the free Microsoft AJAX framework.
• Google Web Toolkit (GWT)
Write in Java and generate JavaScript.
• Direct Web Remoting (DWR)
Easily make calls on Remote Java Objects through
JavaScript.
• Dojo
A free JavaScript library increasing the level of abstraction.
• Prototype
A JavaScript Framework that aims to ease development
95-733
Internet
Technologies
of dynamic
web
applications.
Management
58
jQuery AJAX Example
<!DOCTYPE html>
<html>
<head>
<script src="jquery.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("div").load('test1.txt');
});
});
</script>
</head>
<body>
The syntax is: $(selector).action()
A $ sign to define/access jQuery
A (selector) to "query (or find)"
HTML elements
A jQuery action() to be performed
on the element(s)
Document ready before running
jQuery.
<div><h2>Let AJAX change this text</h2></div>
<button>Change Content</button>
</body>
</html>
From W3C Schools
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Dojo Ajax Example
dojo.io.bind ( {
Note the use of
url : “getCityState.php?zip=“ + zip,
JSON to describe
load: function( type, data, evt ) {
an AJAX call.
var place = data.split(‘, ’);
if(dojo.byID(“city”).value = “”
dojo.byID(“city”).value = place[0];
if(dojo.byID(“state”).value = “”
dojo.byID(“state”).value = place[1];
},
error: function(type, data, evt ) {
alert(“Error in request, returned data:”+data);
},
method: “GET”,
mimetype: “text/plain”
}
From Pg. 414
);
Of Sebesta
Management
60

95-733 Internet Technologies Lecture 1: Introduction 1 Master of Information System

Transcription

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