Getting Started with AJAX using Java

AJAX is an acronym for Asynchronous JavaScript And XML. AJAX provides an ability to communicate with the server asynchronously. Here asynchronous is the keyword. To explain that in simple terms, you can send a request to server and continue user interaction with the user. You need not wait for response from the server. Once the response arrives, a designated area in UI will update itself and reflect the response information. Whole page need not be reloaded.

This is achieved by AJAX using XMLHttpRequest object. Your browser provides the capability for XMLHttpRequest object. Most modern browsers provides support for XMLHttpRequest. This object helps for http request and process XML response. It is not mandatory that you should use only XML. Simple text can also be used in Ajax but which is uncommon.

Before continuing with the article, I assume that you have basic knowledge about http headers, request response mechanism, different method types and response codes. If you lack knowledge in these areas, it is better to update them before proceeding. If you cant read GET, POST, HTTP status 200 OK and response Content-Type: text/html, xml then you must know these topics before learning AJAX. I am not writing in detail about them here, because each one of them calls for a detailed separate article.

Let me write a HelloWorld ajax web application to demonstrate basics. We shall have a button with name ‘Say Hello!’ On click of that button, without reloading the whole page we will display “Hello World!” by replacing the ‘Say Hello!’ button. Following source code listing contains complete code of sample web application.

index.jsp

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
	<title>Getting Started with AJAX using JAVA</title>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<script type="text/javascript" language="javascript" src="ajax.js"></script>
</head>
<body>
	<div>Getting Started with AJAX using JAVA: Hello World!</div>
	<div id="hello"><button type="button" onclick="makeRequest()">Say Hello!</button></div>
</body>
</html>

index.jsp contains a div ‘hello’. That is the div which XMLHttpRequest object is going to overwrite with response from Servlet. On click of the button we call a java script function makeRequest(). Until now, there is nothing special. Its usual jsp and javascript call. Ajax is not in the picture.

Now go through makeRequest() given below. Inside that we call getXMLHttpRequest() which returns a XMLHttpRequest object. That can be used as a utility method in all your AJAX programs. Thats an attempt to standardization. Different versions of browsers provide different ways of creating XMLHttpRequest. We are covering all possible combinations inside that method.


Once we get XMLHttpRequest object, we need to register a function which will be called on state change. Now its time to explain in detail about XMLHttpRequest object.

XMLHttpRequest properties and events

XMLHttpRequest consists of properties readyState, status, statusText, responseText and responseXML.

  • readyState denotes states as 0 – UNINITIALIZED, 1 – LOADING, 2 – LOADED, 3 – INTERACTIVE, 4 – COMPLETE.
  • status is HTTP status code for the response
  • statusText is HTTP status message for the status code
  • responseText is response text from server
  • responseXML is DOM document object of reponse XML document from server

XMLHttpRequest contains an event ‘onreadystatechange’. It is invoked whenever ‘readyState’ property given above changes.

We need to register a function for the above event ‘onreadystatechange’. In our makeRequest(), after getting xmlHttpRequest object we register getReadyStateHandler(xmlHttpRequest). Therefore whenever there is a state change, this function will be called by the XMLHttpRequest / browser.

After registering the callback funtion we set the request url as the HelloWorld servlet. In web.xml we have done the servlet mapping for that servlet.

In getReadyStateHandler function, if readyState is 4 and http status code is 200 then we set the reponse text from XMLHttpRequest object to the div hello in index.jsp.

ajax.js

/*
 * creates a new XMLHttpRequest object which is the backbone of AJAX,
 * or returns false if the browser doesn't support it
 */
function getXMLHttpRequest() {
	var xmlHttpReq = false;
	// to create XMLHttpRequest object in non-Microsoft browsers
	if (window.XMLHttpRequest) {
		xmlHttpReq = new XMLHttpRequest();
	} else if (window.ActiveXObject) {
		try {
			// to create XMLHttpRequest object in later versions
			// of Internet Explorer
			xmlHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (exp1) {
			try {
				// to create XMLHttpRequest object in older versions
				// of Internet Explorer
				xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (exp2) {
				xmlHttpReq = false;
			}
		}
	}
	return xmlHttpReq;
}
/*
 * AJAX call starts with this function
 */
function makeRequest() {
	var xmlHttpRequest = getXMLHttpRequest();
	xmlHttpRequest.onreadystatechange = getReadyStateHandler(xmlHttpRequest);
	xmlHttpRequest.open("POST", "helloWorld.do", true);
	xmlHttpRequest.setRequestHeader("Content-Type",
			"application/x-www-form-urlencoded");
	xmlHttpRequest.send(null);
}

/*
 * Returns a function that waits for the state change in XMLHttpRequest
 */
function getReadyStateHandler(xmlHttpRequest) {

	// an anonymous function returned
	// it listens to the XMLHttpRequest instance
	return function() {
		if (xmlHttpRequest.readyState == 4) {
			if (xmlHttpRequest.status == 200) {
				document.getElementById("hello").innerHTML = xmlHttpRequest.responseText;
			} else {
				alert("HTTP error " + xmlHttpRequest.status + ": " + xmlHttpRequest.statusText);
			}
		}
	};
}

A simple Hello World servet sending response as Hello World! as text.

HelloWorld.java

package com.javapapers.sample.ajax;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorld extends HttpServlet {

	/**
	 * A simple HelloWorld Servlet
	 */
	public void doPost(HttpServletRequest req, HttpServletResponse res)
			throws java.io.IOException {
		res.setContentType("text/html");
		res.getWriter().write("Hello World!");
	}

	public void doGet(HttpServletRequest req, HttpServletResponse res)
			throws java.io.IOException {
		doPost(req, res);
	}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>Getting Started with AJAX using JAVA</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>helloWorld</servlet-name>
    <servlet-class>com.javapapers.sample.ajax.HelloWorld</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>helloWorld</servlet-name>
    <url-pattern>/helloWorld.do</url-pattern>
  </servlet-mapping>
</web-app>

Output of Hello World AJAX

Before AJAX call:

After AJAX call:

I have used text response to demonstrate AJAX. There is a lot more to AJAX. I will get into using XML, advanced techniques and jquery in future articles.

This AJAX tutorial was added on 21/07/2010.

Comments on "Getting Started with AJAX using Java" Tutorial:

  1. Praveen Kumar Jayaram says:

    Great!
    Such a short and simple example to understand AJAX :)

  2. Anonymous says:

    thanks for posting

  3. Anand Garlapati says:

    Good article. It is very stright forward and no mess in explaination.

    Please post the article on AJAX with XML as one example and JQuery.

    Thanks
    Anand Garlapati

  4. Shalini Gupta says:

    Good Artical and helpful for beginners!!!

  5. Juanje says:

    great! very simple, and the base to understand the use of complex frameworks!

  6. Vijay says:

    Thanks a lot! I wasted a lot of time to run hello ajax using java until i found this one.God Bless U! Keep Helping!!!!!!

  7. Ram says:

    HI,

    I don’t have any server to execute the above program.If I execute it,am getting alert with “Http Error 2:Unknown” Is it possible to execute in my local system without any server.

    Regards
    Ramesh

  8. MArco says:

    Hi,

    I too prefer to use jquery.

  9. subbu says:

    Nice one. Also Please explain JSON with AJAX

  10. james says:

    how to make calculator using ajax?

  11. Anto says:

    superb

  12. Lino says:

    Great tutorial! I was trying a different tutorial (found here http://www.hiteshagrawal.com/ajax/ajax-programming-with-jsp-and-servlets) and they failed to mention updating the web.xml file. Your tutorial is much better thank you!

  13. Prasanna says:

    Nice tutorial ..very helpful

  14. swathi says:

    Hi,
    I have three jsp pages.
    in first jsp page i have one add button when this is clicked i made a call to ajax function
    now the ajax is called and kept the contents in first jsp
    now the contents which are added are one select list and textfield
    now when i click the select list which was added again i have to call ajax and should keep the contents of third jsp..
    is it possible to call ajax like this
    pls reply me………

  15. Naresh says:

    I Love this Example… It Was Simply Superb..Explaining the whole flow in a single basic example, it was really good one….!!!!

    Hey Can u Just Help me in drag and drop events in ajax, I need to create a form builder in java by using ajax, Can i expect good examples on that… Waiting for your reply… :-)

  16. Ragu` says:

    This ajax tutorial really simple and superb. Keep it up

  17. Somdev says:

    Lots of thanks for u, such a great example.

  18. Miguel Angel says:

    El mejor ejemplo para empexar con ajax que he visto en la red

  19. showni says:

    HI,

    im getting HTTP ERROR 404:

    WHILE excecute above prgm.. plz help me

  20. prabhu says:

    Hi,

    Nice one,i understood the basic working of Ajax,i need some complicated examples……..

    thanks a lot for giving this article….

  21. jyoti says:

    thanks 4 the description

  22. srinivas says:

    hi,
    I tried this above example, but im getting two errors “XMLHttpRequest cannot be resolved to a type” and “ActiveXObject cannot be resolved to a type”..

    Plz provide solution for this…

    Thanks,
    srinivas G.

  23. Randeep says:

    Hi sir,
    your website helped me to do lot of works in my firm,
    now i need a help from you, i am creating a web application like facebook sharing proceess with java and oracle.
    So i need some help from you, how to make the sharing process?

    Thanking you.

  24. jyoti says:

    your article is very good.it help me alot.

  25. Manoj says:

    simple but too good

  26. Rajesh Takkellapati says:

    Excellent Sir. We have learnt a lot from this tutorial.

  27. Anil says:

    Neat & Clean in each & every post.. i went through more than half of your posts until just never get that much info on a single site..

    Please post regarding Jquery & Spring Framework also.

  28. Bipraraj says:

    Very Useful Material of AJAX and Java. Basically important for every begineers like me.

    Thank you very much.

  29. Dinesh kumar says:

    Very Useful Material of AJAX and Java. Basically important for every begineers like me.

    Thank you very much.
    its simple laugage use…

  30. Vinoy says:

    Gr8 very good and small example .very well we can understand .Gr8 effort

  31. Anonymous says:

    please set download link on page…..

  32. Ben says:

    This is very well designed from the page layout to the introduction of components and explanations. Very nice Joe!

  33. madhu says:

    easy to understand for beginner .

  34. Anonymous says:

    provide coding with tutorials

  35. Ganesh says:

    Asam fro beginers

  36. Ganesh says:

    Asam for beginners

  37. Ganesh says:

    it is very easy to understand

  38. Ashish Namdev says:

    Is it very easy ..
    thank you for such best explanation…

  39. vj says:

    good explanation for beginners.. thanks

  40. Abhinav Sharma says:

    Hi!
    I want to upload an image
    It will go like this
    Browse an image
    Click on Upload button
    When the button on an HTML Page is clicked, it will call an AJAX function which will call Servlet so that page doesn’t get refreshed. After processing on server side, the page should display the uploaded image(if successful) or error message(in case not uploaded).

    Please give some idea that how do establish communication from AJAX to Servlet and then from Servlet to AJAX, and also what to pass from AJAX to Servlet and also what to catch from Servlet to AJAX.
    Please help me out.
    Regards
    Abhinav

  41. Rohan says:

    That was good code i was searching from a long time and your blog helped me a lot.

  42. Mahesh babu says:

    Nice Example. Good for beginners to take a step over in ajax.

  43. Anonymous says:

    It’s a good stuff to start with and clear for any new developer
    Thank YOu for posting it.

  44. Rashi says:

    Really a very nice tutorial.. Thanx a lot..

  45. Fareed says:

    Thanks Q very much

    its really excellent example for beginner

  46. Prudhvi says:

    A Simple Example for Beginners.

    ThankYouVeryMuch

  47. vishal says:

    Perfect Sir..
    I was looking for similar example to understand very basic concept of using ajax with servlets and jsp.

    Thanks a lot.

  48. Manikandan says:

    dear sir,

    i can understand the ajax concept,but i need populating the dropdownbox.

    if i select one dropdwonbox value, the next dropdownbox value will be change according to the first dropdownbox.

    for exanple;

    if i select country the state dropdownbox will be change according to country dropdownbox

    can you help me…

    Thanks

  49. Vasudev says:

    Thanks for such a Nice article!

  50. pasha says:

    this is well for ajax beginers thanks for ur blogs…..

  51. Aravindh says:

    Simply useful. Also the Javapapers.com website is super.!!!!Hands of…

  52. suresh says:

    very useful.. thx

  53. Anonymous says:

    Hi Joe,
    Nice Article, please post article using xml also it is really helpful.
    Ranjit

  54. vishnudev says:

    nice example.
    can you give an example for returning json object for theajax request.

  55. pankaj says:

    very good and simple ajax tutorial. Thanks for this.

  56. Subhash says:

    This is good Program for beginners and intermediate

  57. Gootam says:

    Good Work Joe.. please keep it up.

  58. Naresh says:

    Simply Superb!! Good blog for AJAX-beginners like me.
    Thanks a lot.

  59. Anonymous says:

    This blog is really awesome.
    Joe your way of explaining concepts is very simple and helpful. Your all blogs are very informative. Thanks !!

  60. Sumon says:

    Great Job!! Carry on Joe

  61. Maheswar Reddy says:

    Very Nice Article for beginners & Easy to understand for implementing.

  62. sri says:

    this is very good to rad and see..such a great job done by you..very good site..

  63. nithin says:

    nice 1

  64. Nagappa says:

    Nice page..:P

  65. Sathyajith says:

    nice

  66. Sudha says:

    Nice tutorial..
    Similar example works fine.
    But I am facing a problem while calling the servlet from a JSP page which is under some folder under web-content.

    should I add any path prefix to the servlet URL pattern other than that mentioned in Web.xml.

    Could anyone please help..

    Thanks,
    Sudha

  67. Abhishek says:

    Hello Sir,

    This was the great tutorial about ajax and any one who is new in web tech, can easily learn ajax from hear, but I have another question about Comet.
    As I surf so many sits but didn’t get any satisfactory answers or example about the same. but what i learn, Comet is nothing but reverse ajax. So can you help me on this topic?

  68. Nagendra says:

    Very Nice Article for beginners & Easy to understand for implementing.

  69. Ramanujam says:

    Hai Joe,I read your java related stuff,it is very interesting and very usefull also.Can you publish about Junit testing in your next Article.Thank for your knowledge sharing

  70. rajesh says:

    could you please post some more examples ??
    It will be very helpful.
    thanks

  71. Anonymous says:

    the article was very helpful joe

  72. fakru says:

    ye kya chutiya pa hai yaar kuch or dalo example me

  73. Anonymous says:

    Thank u Joe good article. very useful

  74. Kavita says:

    Sir,I got an error at the end of return function()

    error is: syntex error when we close return function at this place };

    return function()
    {
    if (xmlHttpRequest.readyState == 4)
    {
    if (xmlHttpRequest.status == 200)
    {
    document.getElementById(“hello”).innerHTML = xmlHttpRequest.responseText;
    } else
    {
    alert(“HTTP error ” + xmlHttpRequest.status + “: ” + xmlHttpRequest.statusText);
    }
    }
    };

  75. Anonymous says:

    HI Joe, If possible can you please explain the Country–>State–> City example using Ajax.

    Thanks in advance

    Bhabani

  76. Pradeepkumar says:

    Nice Description ,thank you for post .

  77. Anonymous says:

    its very helpful !!

  78. Anonymous says:

    Nice article

  79. Filip says:

    Ty dude. Very helpfull.

  80. pawan bmr says:

    Hats of you
    Realy great Blog and great work
    Good job keep it up ,We all programmer proud of you..
    Thanks

  81. Samir says:

    Hi,
    Why are you using a closure in the getReadyStateHandler function?

  82. Prashant Vhasure says:

    Very good article. It is very stright forward and no mess in explaination.

    Please post the article on AJAX update.
    like facebook notification.

  83. Prachi Singh says:

    Short n simple Article….:)

  84. Anonymous says:

    Excellent article for the beginners in Ajax!!

  85. Jake says:

    Waaaaaa Finally something today worked. My Ajax on Java book is totally useless(well not really i knew from the schema in it where your files should be placed in Eclipse).

  86. Navya says:

    Simple example that works and easy to get the concept of AJAX. Exactly what I was looking for..

  87. Subhash Chandra says:

    Superb Website For Java Buddies

  88. shirish says:

    Very nice useful for all java Buddies…
    thank you .

  89. Thiru says:

    Thaks a lot…

  90. Anonymous says:

    Very nice example to understand AJAX easily.

  91. Venkatesh says:

    Great Joe :)

  92. pratyasini says:

    Thanks Joe… For making our task easy….

  93. Anonymous says:

    it is ok, but when we are using tiles in spring, how to take a div id…

  94. Anonymous says:

    good to know!!Thanks

  95. Anonymous says:

    code is working fine in IE but there is some problem with FireFox..(Orogin null) :(

  96. ravi teja says:

    Thank you sir

  97. santosh damre says:

    Thanks Joe for such a simple and understandable Document on AJAX

  98. Yogesh Rathore says:

    thaks… for giving simple example.. this is very good for fresher

  99. Mukesh Kumar says:

    Very Very thanks!
    It is very beneficial for beginner. I start learning ajax with the help of this post.

  100. Anonymous says:

    Thank you. Its a very good example for beginners like me

  101. Ashok says:

    Awesome tutorial dude !!

  102. durga prasd reddy says:

    how to maintain the drop down list data static after submitting ?
    please send the reply ASAP.

  103. Ritu Rai says:

    Good tutorial for a fresher…

  104. Anand Jain says:

    thank..it was easy to understand..:)

  105. Anonymous says:

    hi ,

    i tried the above example but i am getting a popup 404 http not found when i click on say hello !!

    Please help

  106. Shikha says:

    Thanks for posting

  107. Paula says:

    Thanks!!

  108. yaswanth says:

    very nice tutorial

  109. Pradip Bhatt says:

    Yes… Its very good example.
    At the beginer stage, we have to starting with this. But after clearing concept we must have to use Ajax with Jquery, its very easy also.

    So.. Joe please post some nice example Ajax with Jquery Demo.

  110. Rajendra says:

    After getting the reposne from JSP i want to check where it is success or failure in javascript.

    like
    var data = ajaxObject.responseText;
    if(data ==”success”)
    alert(data);
    else
    alert(“failure”);

    But i was failed in getting success data.
    please help

  111. Kumar says:

    Hi Joe,

    I have a problem using Ajax or Javascript in my development. I am developing a package which is based on client-server method. i have a java package(jar) which is used to display a file properties in GUI mode on client side. i placed that jar file in the webserver. while i am trying to access or invoking the java class from javascript/ajax, i could not deploy it. Can you suggest any ways to deploy the jar file to execute on client side.?

  112. Nikhitha says:

    This is a very good tutorial.But i have a query. I tried this code with a jsp page. In my case the state of xmlHttp request changes from 0 to 1.But it never becomes equal to 4. So i am unable to proceed .Could you please help me in this regard.It would be very kind of you.

  113. manjunath s b says:

    thanku thanku……..

  114. shashikant says:

    very nice easy explanation.

  115. jagnya says:

    Why we use —

    xmlHttpRequest.setRequestHeader(“Content-Type”,
    “application/x-www-form-urlencoded”);

  116. santosh kumar says:

    first of all..i would like to thanks u for ur very short and simple example.can u plz guide me for hosting new personnel website..

  117. mohsen says:

    thanks man !
    also i had lots problem with these issue but finally solved
    by use your code

  118. ajit says:

    Simple and easy to understand as usual.
    That’s your trademark Joe.
    Keep up this good work of making people understand the concepts.

  119. Rama Kamath says:

    Hey can you suggest any book to learn AJAX with Java Examples?

    I’m new to AJAX. This is just what I was looking for.

    Hey your program works like a charm. Thank you so much. God Bless you.

  120. Ashish says:

    How to send data using xmlHttpRequest.send and get value in servlet

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