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.

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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.

previous post: JAG is Now Unemployed!

next post: Type Erasure

167 comments on “Getting Started with AJAX using Java

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

  2. 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

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

  3. Good Artical and helpful for beginners!!!

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

  5. Very Good Example with explaination.

  6. 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. 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. Nice one. Also Please explain JSON with AJAX

  9. 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………

  10. 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… :-)

  11. This ajax tutorial really simple and superb. Keep it up

  12. Lots of thanks for u, such a great example.

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

  14. HI,

    im getting HTTP ERROR 404:

    WHILE excecute above prgm.. plz help me

  15. Hi,

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

    thanks a lot for giving this article….

  16. 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.

  17. 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.

  18. your article is very good.it help me alot.

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

  20. super sir,i has learn more information your blog

  21. Hi,
    I want to ask how to send parameters to .java file thorugh ajax call?

    Thanks :)

  22. 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.

  23. nice….provide the app as downloadable file…..

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

    Thank you very much.

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

    Thank you very much.
    its simple laugage use…

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

  27. please set download link on page…..

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

  29. I DONT KNOW ABOUT AJAX.. BUT NOW I HAVE AN IDEA AND I CAN IMPLEMENT ….VERY USEFUL CODE FOR ALL…CONGRATS…
    THANKS TO U….

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

  31. 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

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

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

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

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

  36. Thanks Q very much

    its really excellent example for beginner

  37. A Simple Example for Beginners.

    ThankYouVeryMuch

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

    Thanks a lot.

  39. 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

  40. We need more topics on Ajax with webservice.

  41. Cricp and nice. Got the basic understanding. Thank you.

  42. Crisp and nice. Got the basic understanding. Thank you.

  43. it is a good one to who all unknown about ajax

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

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

  46. very good and simple ajax tutorial. Thanks for this.

  47. This is good Program for beginners and intermediate

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

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

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

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

  52. 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

  53. 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?

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

  55. 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

  56. very nice tutorial. It is very helpful to understand basics of ajax.

  57. Very useful artical which makes clear

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

  59. ye kya chutiya pa hai yaar kuch or dalo example me

  60. Thank u Joe good article. very useful

  61. 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);
    }
    }
    };

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

    Thanks in advance

    Bhabani

  63. Nice Description ,thank you for post .

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

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

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

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

  67. Excellent article for the beginners in Ajax!!

  68. 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).

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

  70. Superb Website For Java Buddies

  71. Very nice useful for all java Buddies…
    thank you .

  72. Very nice example to understand AJAX easily.

  73. hello joe
    Nice………..

    but Please tell me how to create my own blog using java coding sir please help me…………

  74. Good work bro…..

    Regards
    Ravi Likhar

  75. Nice example Joe.. very useful..

    Regards,
    Om

  76. Perfect!! Nice to see your blog layout too..

  77. It is very easy to understand. Ajax call can be changed from async to sync . that part is missing dude

  78. AWESOME,,,, JOE…. u explained from scratch to end..

  79. Hi JOE,

    I am getting 404 error,Could please suggest me> What I have to do..?

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

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

  81. Thanks Joe for such a simple and understandable Document on AJAX

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

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

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

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

  86. hi ,

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

    Please help

  87. 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.

  88. Best Ajax article for beginners. Great work!

  89. 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

  90. 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.?

  91. I appreciate the way u wrote article…..thank you.

  92. good one … a clean reference …

  93. this information was very helpful to me..

  94. Adding to the big list of appreciation. Wonderful site for understanding AJAX. Thanks

  95. You made my day simple – Many thanks :)

  96. 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.

  97. Hi Sir,

    I am beginner for ajax.I use the above code to check.
    At the time of clicking the say hello button , it shows the page without refreshing.
    can you reply.

  98. Excellent tutorial. Super. Please provide Ajax code for country state dropdowns in jsp, java

  99. Why we use –

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

  100. 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..

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

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

  103. 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.

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

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