Techie Baba

Official Google Blog: Google accounts on Twitter

2009-07-12T12:36:00.000-04:00

Official Google Blog: Google accounts on Twitter

HelloWorld in Struts 2.0

2008-09-22T11:38:00.003-04:00

IDE: Eclipse (Version: 3.4.0)
Struts2: Version 2.0.11.2
Web Server: Apache Tomcat 6.0.18

Step 1) Create a new "Dynamic Web Project" using File -> New -> Dynamic Web Project.
Project Name: Struts2Demo
Context Root: Struts2Demo
Content Directory: WebContent
Java Source Directory: src

Step 2) Copy the following jars from Struts' lib[C:\struts-2.0.11.2\lib] to the Web-Project's lib directory (WebContent/WEB_INF/lib) [Minimum required set]
commons-logging-.jar
freemarker-.jar
ognl-.jar
struts2-core-.jar
xwork-.jar

Step 3) Create a new JSP file (HelloWorld.jsp):

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib prefix="s" uri="/struts-tags" %>

<html>
<head>
<title>Hello World!</title>
</head>
<body>
<h1>This is a test!</h1>
<h2><s:property value="message" /></h2>
</body>
</html>

Step 4) Create the action class (HelloWorld):

package com.struts2demo.action;

import com.opensymphony.xwork2.ActionSupport;

public class HelloWorld extends ActionSupport {
public static final String MESSAGE = "Struts is up and running ...";

public String execute() throws Exception {
setMessage(MESSAGE);
return SUCCESS;
}

private String message;

public void setMessage(String message){
this.message = message;
}

public String getMessage() {
return message;
}
}

Step 5) Modify web.xml:

<?xml version="1.0"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
<display-name>Struts2Demo</display-name>
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>

<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

<welcome-file-list>
<welcome-file>HelloWorld.jsp</welcome-file>
</welcome-file-list>
</web-app>

Step 6) Create struts.xml in classpath (here in java source "src" folder):

<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<package name="struts2demo" extends="struts-default">
<action name="HelloWorld" class="com.struts2demo.action.HelloWorld">
<result>/HelloWorld.jsp</result>
</action>

</package>
</struts>

Step 7) Deploy the application to tomcat and start the server:
http://localhost:8080/Struts2Demo/ : you can see HelloWorld.jsp (with no message from server)
Now try,
http://localhost:8080/Struts2Demo/HelloWorld.action
you can see message "Struts is up and running ..." which was set in HelloWorld.java

This article has moved now to new my new BLOG.

MyEclipse Blue vs IBM RAD

2008-09-11T16:18:00.003-04:00

I was exploring whether we can replace IBM RAD with MyEclipse Blue.

To see the presentation click here.

This article has now moved to my new BLOG.

Clustered Index Vs Non-clustered Index

2008-08-20T16:20:00.001-04:00

A database index is a data structure that is used for faster retrieval of data from a database table.

Clustered Indexing: Indexing is done on physical storage. Therefore you can have only one clustered index per table. Generally clustered index is built using Primary Key.

Non-clustered Indexing: Indexing is done logically. Therefore you can have multiple non-clustered indexes per table.

Since, a table can have just one Clustered Index, indexing need to be done carefully. In general scenario apply clustered index unique (PK), most queried column.

Sometime, you may need to work with other non-sorted columns such as Name, Description ( especially , varchar/char typed columns ). Then your physical data store cannot be ordered physically. In this case, you should use Non-Clustered Index for these columns. Because Non-Clustered Indexes can have logical sorting order.

This article has now moved to my new BLOG.

How to convert Java String to DOM document Object?

2008-04-07T17:58:00.003-04:00

It's a simple thing to do.
Just provide String Object as an InputSource or
InputStream to DocumentBuilder.

Example:
String xmlString; 
DocumentBuilderFactory factory =
  DocumentBuilderFactory.newInstance();

DocumentBuilder builder = factory.newDocumentBuilder();

Document document =
 builder.parse(new InputSource(new StringReader(xmlString)));

This article has moved to my new BLOG.

My wikipedia post

2008-03-04T10:27:00.000-05:00

http://en.wikipedia.org/wiki/Output_display_data_unit

Struts 2.0 Explained in Brief!

2007-12-19T18:05:00.001-05:00

HighLights of Struts 2.0:

Action classes are simplified POJOs (Plain Old Java Objects). Any Java class with execute() method can be used as an Action class.
Struts 2 doesn't supports the ActionForm.
Most of the configuration elements in the Struts 2 configuration have default values, so there is no need to set values unless you need to change the default value. This helps reducing the configuration requirement.
Interceptors: Struts 2 introduces a new concept in the framework i.e. interceptors. Interceptors can be executed before and after an Action class is executed. Interceptors are configured to apply common functionality to a request like validation, checking session, etc. All the request pass through a set of interceptors before they are sent to an Action class and after the execution of Action class request passes through the interceptors again in the reverse order.
Struts 2 tags provides support for AJAX.
Framework automatically tracks checkboxes; if a checkbox is missing, the default value "false" is assumed.
Plug-in: Struts 2 extensions can be installed by just dropping the jar files into /WEB-INF/lib directory. No manual configuration is required.

Architecture Explained:

Fig 1. The diagram describes the framework's architecture.

Struts 2 is based on standard technologies such as Java filters, JavaBeans, ResourceBundles, Locales and XML, as well as few open source packages such as OGNL(Object Graph Navigation Language) and XWork.

How Struts 2.0 Framework works (in brief):

An initial request goes to the servlet container where it passes though a chain of filters.
Request passes through an optional ActionContextCleanUp filter (useful if integrating with other technologies).
Then the FilterDispatcher (required) is called, which uses the ActionMapper to determine whether there is a need to invoke an action for this request. If yes, it delegates the control to the ActionProxy.
ActionProxy utilizes the framework configuration files manager, which is initialized from the struts.xml file. ActionProxy creates an ActionInvocation, which is responsible for implementing the command pattern.
The ActionInvocation process invokes the required interceptors and then invokes an Action.
Once the Action is executed, the ActionInvocation is responsible for looking up the proper result associated with the Action result code mapped in struts.xml.
Result is then executed, which, most of the time, renders a JSP or template written using FreeMarker or Velocity.
Interceptors are executed again after completing the Action in the reverse order.
If the ActionContextCleanUp filter is configured, the FilterDispatcher will not clean up the ThreadLocal ActionContext. If the ActionContextCleanUp filter is not configured, the FilterDispathcer will clean up all the ThreadLocals present.

NOTE : (ActionContext has the complete details of the runtime request and response. The framework uses ThreadLocal in connection with the ActonContext class to make the configuration and other runtime details available.)

Major Differences from Struts 1:

Filters have replaced servlets in Struts 2. In web.xml the tags and tags to map the controller, ActionServlet has been replaced by and tags to map the dispatcher, FilterDispatcher.
ActionForms are obsolete now. Properties are part of the Action class.
The default name of configuration file is struts.xml (this file should reside on the classpath of the webapp, generally /WEB_INF/classes).
Struts 1 Actions are singletons and hence need to be thread-safe, since only one instance of the class will be available to handle all request for that Action. Struts 2 Actions are not singletons; they are instantiated for each request, and hence they need not be thread-safe.
Struts 1 Actions use the Servlet API and hence are HTTP dependent. Struts 2 Actions are not coupled to a container and hence are HTTP independent.
Unit Testing: In Struts 1 Actions can't be tested separately. Struts 2 Actions can be tested easily with the support of dependency injection. Actions can be instantiated with the properties set and the method invoked.
Struts 2 supports Java 5 annotations, which can be used as an alternate to XML files.

There are quite few more changes

This article has now moved to my new BLOG.

Google Web Toolkit (GWT) & Eclipse

2007-12-05T11:09:00.001-05:00

Step 1) Create Eclipse Project:
C:\gwt-windows-1.4.60>projectCreator -eclipse ShankyDemoPrj -out myCode/ShankyDemoDir

Step 2) Create GWT Code Sample:
C:\gwt-windows-1.4.60>applicationCreator -eclipse ShankyDemoPrj -out myCode/ShankyDemoDir com.shankydemo.client.GWTDemo

Step 3) Setup Internationalization:
C:\gwt-windows-1.4.60>i18nCreator -eclipse ShankyDemoPrj -out myCode/ShankyDemoDir com.shankydemo.client.GWTDemoConstants

Fig 1: Shows output at Command Line after running the above commands.

To create/update the Java constant file run the newly created "-i18n.cmd" in the root folder and it would generate/update the Java constant file.

Step 4) Import the project created to Eclipse (as shown in figures below):

Fig 2: Import Menu in Eclipse.

Fig 3: Select "Import Existing Project into Workspace".

Fig 4: Click Finish and Project is imported into Eclipse's Workspace.

If you want to add a specific CSS file into project:
Add following into the .gwt.xml file:

within the tags.

This article has moved to my new BLOG.

Can you change innerHTML of IFRAME?

2007-11-07T15:07:00.000-05:00

IFRAME tag in HTML doesn't has innerHTML attribute/property which could have been used to change the content of IFRAME without changing "SRC".

If your IFrame is defined like : <iframe name='myIFRAME' > </iframe>

In your javascript function you can change innerHTML of IFRAME using:

document.myIFRAME.document.body.innerHTML = 'yourHTML';

similarly you can change innerHTML of components inside the IFRAME:

document.myIFRAME.document.getElementById('your_element_id').innerHTML = 'yourHTML';

File Upload using STRUTS

2007-11-06T18:10:00.001-05:00

1. HTML code snippet for file upload:

<FORM name="uploadForm" ENCTYPE='multipart/form-data' method="POST" action="/Upload.do">
<LABEL FOR="theFile">File to be Uploaded:</LABEL>
<INPUT TYPE="file" NAME="myFile">
<INPUT TYPE="submit" NAME="uploadButton" value="Upload File">
</FORM>

You need to specify ENCTYPE attribute of the FORM as 'multipart/form-data' to submit the file as a part of POST request.

2. Create an ActionForm:
ActionForm has a property having same name as file input field in the HTML (<INPUT TYPE="file" NAME="myFile">)

public class UploadFileForm extends ActionForm {
private FormFile myFile;

public FormFile getMyFile() {
return myFile;
}

public void setMyFile(FormFile file) {
this.myFile = file;
}
}

3. Changes in struts-config.xml

Form Bean:
<form-beans>
<form-bean name="uploadFileForm" type="com.shashank.UploadFileForm">
</form-bean>

Action Mapping:
<action-mappings>
<action path="/Upload" type="com.shashank.UploadAction" name="uploadFileForm">
<forward name="success" path="/jsp/Uploader.jsp" />
<forward name="failure" path="/jsp/error.jsp" />
</action>
<action-mappings>

4. Action Class:

public class UploadAction extends Action {

public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
try {
UploadFileForm fileForm = (UploadFileForm)form;

FormFile myFile = fileForm.getMyFile();
if (myFile != null) {
String fileName = myFile.getFileName();
String filePath = "/upload"; //define the directory where you need to upload

/* Save file on the server */
if(!fileName.equals("")) {
File file = new File(filePath );
file.mkdirs();

File fileToCreate = new File(filePath, fileName);
if(!fileToCreate.exists()) {
FileOutputStream fileOutStream = new FileOutputStream(fileToCreate);
fileOutStream.write(myFile.getFileData());
fileOutStream.flush();
fileOutStream.close();
} // END : if(!fileToCreate.exists())
} // END : if(!fileName.equals(""))
} // END : if (myFile != null)
} catch (Exception e) {
e.printStackTrace();
}
} // END of execute()
}

This article has now moved to my new BLOG.

Linus Benedict Torvalds: Father of Linux OS

2007-06-25T13:36:00.000-04:00

Linus was born in Helsinki, Finland, the son of journalists Anna and Nils Torvalds, and the grandson of poet Ole Torvalds. His family belongs to the Swedish-speaking minority (roughly 5%) of Finland's population. Torvalds was named after Linus Pauling, the American Nobel Prize-winning chemist, although he claims he was named after Linus in the Peanuts comic strip. In the book Rebel Code: Linux and the Open Source Revolution, Torvalds is quoted as saying, "I think I was named equally for Linus the peanut-cartoon character," noting that this makes him "a mix of 50 percent Nobel-prize-winning chemist and blanket-carrying cartoon character." Both of his parents were campus radicals at the University of Helsinki in the 1960s.Torvalds attended the University of Helsinki from 1988 to 1996, graduating with a master's degree in computer science. His M.Sc. thesis was titled Linux: A Portable Operating System. From 1997 to 1999 he was involved in 86open helping choose the standard binary format for Linux and Unix.His interest in computers began with a Commodore VIC-20. After the VIC-20 he purchased a Sinclair QL which he modified extensively, especially its operating system. He programmed an assembler and a text editor for the QL, as well as a few games. He is known to have written a Pac-Man clone named Cool Man. In 1990 he purchased an Intel 80386-based IBM PC and spent a few weeks playing the game Prince of Persia before receiving his Minix copy which in turn enabled him to begin his work on Linux.About 2% of the current Linux kernel is written by Torvalds himself[citation needed]. Since Linux has had thousands of contributors, such a percentage is very respectable. Torvalds remains the ultimate authority (aka Benevolent Dictator for Life) on what new code is incorporated into the Linux kernel.Torvalds owns the "Linux" trademark, and monitors use of it chiefly through the non-profit organization Linux International. Linux's wide and passionate userbase makes trademark abuse difficult as misuse is rapidly detected.

Why do a lot of #defines in the Linux kernel use do { ... } while(0)?

2007-06-23T01:24:00.000-04:00

There are a couple of reasons:

Empty statements give a warning from the compiler so this is why you see #define FOO do { } while(0).
It gives you a basic block in which to declare local variables.
It allows you to use more complex macros in conditional code. Imagine a macro of several lines of code like:

#define FOO(x) \
printf("arg is %s\n", x); \
do_something_useful(x);
Now imagine using it like:

if (blah == 2)
FOO(blah);

This interprets to:

if (blah == 2)
printf("arg is %s\n", blah);
do_something_useful(blah);;

As you can see, the if then only encompasses the printf(), and the do_something_useful() call is unconditional (not within the scope of the if), like you wanted it. So, by using a block like do { ... } while(0), you would get this:

if (blah == 2)
do {
printf("arg is %s\n", blah);
do_something_useful(blah);
} while (0);
Which is exactly what you want.

If you want a block statement so you can have several lines of code and declare local variables. But then the natural thing would be to just use for example:

#define exch(x,y) { int tmp; tmp=x; x=y; y=tmp; }
However that wouldn't work in some cases. The following code is meant to be an if-statement with two branches:

if (x > y)
exch(x,y); // Branch 1
else
do_something(); // Branch 2

But it would be interpreted as an if-statement with only one branch:

if (x > y) { // Single-branch if-statement!!!
int tmp; // The one and only branch consists
tmp = x; // of the block.
x = y;
y = tmp;
}
; // empty statement
else // ERROR!!! "parse error before else"
do_something();

The problem is the semi-colon (;) coming directly after the block. The solution for this is to sandwich the block between do and while (0). Then we have a single statement with the capabilities of a block, but not considered as being a block statement by the compiler. Our if-statement now becomes:

if (x > y)
do {
int tmp;
tmp = x;
x = y;
y = tmp;
} while(0);
else
do_something();

AJAX and XML Response

2007-06-10T15:10:00.001-04:00

If you want to return XML as a response to AJAX request, there are few things which needs to be taken care of:

1) Set the content type of the response as xml:
response.setContentType("application/xml");
Otherwise function xmlHttpRequest.responseXML would return a null object and the XML you are trying to return as response would be returned as String object rather than a XML object and you can access that by xmlHttpRequest.responseText.

2) Construct a well-formed XML which you are going to return in response, make the XML as standalone :
returnXML = "<?xml version='1.0' encoding='UTF-8' standalone='yes'?>
<root>
<allxmlelements></allxmlelements>
</root>";
Important: If the XML constructed above is not well formed you won't be able get the correct response back when you try to access the returned XML in JavaScript using:
var rspXml = xmlHttpRequest.responseXML;

Q: How to check if the XML you are returning in AJAX response is correct/well-formed or not?
A: Best way to check whether the returned XML is well formed or not is to type the URL being passed in the AJAX request directly into the browser. If the response XML is well formed then browser would display the complete XML or else it would display error in the XML. (This is the best and easiest way to check the response.)

Example: in an STRUTS application when the AJAX request is processed in an Action class you can return the XML using code below;
response.setContentType("application/xml");
response.getWriter().write(returnXML);
return (null);

Note: In a STRUTS application for an AJAX request to complete successfully, the execute method of the Action class being called should return "null" instead of an ActionForward.

This article has now moved to my new BLOG.

AJAX : A New Approach to Web Applications

2006-11-14T01:09:00.002-05:00

Ever wondered whats behind Google Maps, or Google Suggest, etc. Here I have tried to explain AJAX technology in simple words.

What is AJAX?

AJAX stands for Asynchronous JavaScript And XML. It is a technique used for communicating with the web server to send and retrieve data without loading a new page or reloading the current page.

To do this, the XMLHttpRequest object is used. This object is supported by most modern browsers in one form or another. As the name implies, the object allows you to perform HTTP requests which returns some form of response. The XML part refers to the fact that the object can automatically parse an XML document sent in response to a request.

HTTP Request: When you load a web page in your browser, say "http://www.example.com/index.html", the browser first opens a connection to the host, www.example.com. It then sends the server an HTTP request which consists of several lines of plain text. A typical request may look something like this:

GET /index.html HTTP/1.1

Host: www.example.net

User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12)...

Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,...

Accept-Language: en-us,en;q=0.5

Accept-Encoding: gzip,deflate

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

Keep-Alive: 300

Proxy-Connection: keep-alive

Pragma: no-cache

Cache-Control: no-cache

HTTP Response: The first line contains the HTTP verb or method. In this case, the method is GET which means return the following document. Following that is the path to the document to retrieve (/index.html). The HTTP/1.1 tells the server what version of HTTP the browser supports.

The web server will return a response. Like the request, this consists of several lines of plain text. A typical response to the above request will look something like this:

HTTP/1.x 200 OK

Server: Microsoft-IIS/5.1

Date: Fri, 20 Jan 2006 19:29:47 GMT

Content-Length: 534

Content-Type: text/html

Cache-Control: private

<html >

<head>

<title>About Us</title>

</head>

<body>

<h1>About us</h1>

<p>...</p>

</body>

</html>

The first line contains the HTTP version and a three digit status code. The text following that number is a short description of that code. 200 means "OK," the request was successfully processed. If the requested page did not exist, the status would be "404 Not found."

The lines following are request headers. Like the response headers, these give additional information about the response such as the document type ("text/html") and size (534 bytes).

A blank line follows, signaling the end of the response header. The rest of the lines represent the response data. In this case, it is the HTML of the page which the browser will parse and render.

Passing Data in a HTTP Request:

There are two commonly used ways for a client to pass data in an HTTP request. One is to append a query string to the URL. For example,

http://www.example.com/signup.jsp?name=Shanky+Baba&email=shanky%40baba.com

The second way to pass data on an HTTP request is to use the "POST" method. This is often used with forms on web pages. An example of a POST request generated when a user submits a form is shown below:

POST /signup.jsp HTTP/1.1

Host: www.example.com

User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12)...

Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,...

Accept-Language: en-us,en;q=0.5

Accept-Encoding: gzip,deflate

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

Keep-Alive: 300

Connection: keep-alive

Content-Type: application/x-www-form-urlencoded

Content-Length: 38

name=Shanky+Baba&email=shanky%40baba.com

The XMLHttpRequest Object:

With the XMLHttpRequest object, you can make HTTP requests from within JavaScript code on a web page and access the data returned by the web server.

XMLHttpRequest Object
Properties
readyState	A number representing the current state of the request: 0 - UNINITIALIZED 1 - LOADING 2 - LOADED 3 - INTERACTIVE 4 - COMPLETE
status	The numeric HTTP status code returned by the web server.
statusText	The text associated with the above HTTP status code. For example, 200 means "OK" and 404 means "Not found".
responseText	A string containing the response data returned from the web server.
responseXML	If the web server returns an XML document, this will be a DOM document object representing the parsed XML.
Methods
open(method, url, asynch, username, password)	Initializes a new request. method is the HTTP request verb, usually "GET" or "POST". The last three options are optional: asynch defaults to true, username and password may be specified if the web server requires authentication.
setRequestHeader(name, value)	Sets a named request header.
send(data)	Makes the request. optionally passing data.
abort()	Aborts an active request.
getResponseHeader(name)	Returns the value of the named response header.
getAllResponseHeaders()	Returns a string containg all the response headers.
Events
onreadystatechange	Raised anytime the readystate property changes.

Table 1 : XMLHttpRequest Object

Step 1: Create an XMLHttpRequest Object

The code below can be used to create an XMLHttpRequest object despite the browser differences.

// Define a list of Microsoft XML HTTP ProgIDs.

var XMLHTTPREQUEST_MS_PROGIDS = new Array(

"Msxml2.XMLHTTP.7.0", "Msxml2.XMLHTTP.6.0", "Msxml2.XMLHTTP.5.0",

"Msxml2.XMLHTTP.4.0", "MSXML2.XMLHTTP.3.0", "MSXML2.XMLHTTP",

"Microsoft.XMLHTTP");

// Returns XMLHttpRequest object.

function getXMLHttpRequest() {

var httpRequest = null;

// Create the appropriate HttpRequest object for the browser.

if (window.XMLHttpRequest != null)

httpRequest = new window.XMLHttpRequest();

else if (window.ActiveXObject != null) {

// Probably browser is IE, find the right ActiveXObject.

var success = false;

for (var i = 0; i< XMLHTTPREQUEST_MS_PROGIDS.length && !success; i++) {

try {

httpRequest = new ActiveXObject(XMLHTTPREQUEST_MS_PROGIDS[i]);

success = true;

}

catch (ex) {}

}

// Display an error if we couldn't create one.

if (httpRequest == null)

alert("Error in HttpRequest():\n\n" + "Cannot create an XMLHttpRequest bject.");

// Return it.

return httpRequest;

}

We can then define an XMLHttpRequest object like so,

var myXmlHttpRequest = getXMLHttpRequest();

Step 2: Open a Request

Now we can open a connection to a specified URL using the code below:

myXmlHttpRequest.open("GET", url, true);

Two ways of Parameter Passing through AJAX:

Passing parameter through URL : example http://www.example.com/signup.jsp?name=Shanky

Here you access the variable called “name” in your server code and get the

value “Shanky”.

If you want to pass a larger amount of data to the request we can use POST method. To be able to do this we need to add a request header and pass data in the send() command. Example code:

myXmlHttpRequest.open("POST", url, true);
myXmlHttpRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
myXmlHttpRequest.onreadystatechange = callbackFunctionName
var myform = document.forms[0];
var reqBody = getRequestBody(myform);
myXmlHttpRequest.send(reqBody);

Step 3: Create Response Handler

Since we made an asynchronous request to the server we don’t wait for the server to send the response. So we specify a callback function so that when server finishes its job it can notify the callback function of its response.

XMLHttpRequest object has a property called readyState that contains values depending upon the current status of the request. (Refer Table 1 for details.)

We have an associated event handler onreadystatechange using which we can specify a call back function when server processing is over and the readyState has a value of 4 (i.e. complete).

myXmlHttpRequest.onreadystatechange = callbackFunctionName

An example response handler function (a Javascript function):

function callbackFunctionName() {

if(myXmlHttpRequest.readyState == 4) {

if(myXmlHttpRequest.status == 200) {

//Write your action

Document.getElementById(‘id’).innerHTML =

myXmlHttpRequest.responseText;

} else {

alert(“Error: HTTP “ + myXmlHttpRequest.status + “ : “

+ myXmlHttpRequest.statusText);

} //end else

} // end if

} //end function

Step 4: Send the Request (or submit the request to server)

The last and final step to complete your AJAX application is to send the XMLHttpRequest object to the server.

myXmlHttpRequest.send(null);

or, myXmlHttpRequest.send(data);

where ‘data’ can be a piece of data to be send to the server as shown in sample code in Step 2, where we send the form data of html to the server.

Some Miscellaneous stuff:

Response Type: We can check the content type of the response in the response header. Normally the response that we are expecting to get back will be either an XML or a plain text. This can be checked by following code:

var cType = this.getResponseHeader("Content-Type");

if (cType == 'text/xml') {

// XML response
} else if (cType == 'text/plain') {

// plain TEXT response
} else {

alert('unknown content type');

}

Aborting A Request: Since AJAX is processed asynchronously, we can limit the request to just one request through some minor alteration in the code:

Replace

var myXmlHttpRequest = getXMLHttpRequest();

With this

if (!myXmlHttpRequest)

myXmlHttpRequest = createXMLHttp();
else if (myXmlHttpRequest.readyState != 0)

myXmlHttpRequest.abort();

This article has now moved to my new BLOG.

Booting this blog :)

2006-08-31T02:08:00.000-04:00

Hi Everybody,
I am so called "Linux Kernel developer" and mainly working in File systems. But still I am in learning phase. I have worked on lots of technologies in my short career. So may be sometimes I'll be able to help u in that.

Thanks to "Techie Baba" for creating this Blog.

Rgds,
Adil

A brief-up from Khushi

2006-08-30T16:24:00.000-04:00

Hello Everyone :)

I work as a J2EE Developer and am currently involved in developing a sales application.
Don't really know what exactly this blog aims to be a platform for, but am excited about the vox-populli.
Nice initiative ......Shanky.........but only Techie "BABA"......bahut nainsaafi hai Thakur ;)

Test

2006-08-29T10:11:00.000-04:00

This is just a test post!

Would be coming soon with some techincal posts. Related to J2EE web applications.

Keep checking!