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copied!<p>First create a Servlet class which returns the desired response based on the request. It can be HTML, XML or JSON. I'd suggest to use <a href="http://www.hunlock.com/blogs/Mastering_JSON_%28_JavaScript_Object_Notation_%29" rel="nofollow noreferrer">JSON</a> for this since that's the most easiest produceable in Java and consumeable in JavaScript. You can use for example <a href="http://code.google.com/p/google-gson/" rel="nofollow noreferrer">Google Gson</a> to convert from a fullworthy Java object to a JSON string (and vice versa). E.g.</p> <pre><code>protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOexception { // Populate response data somehow. Can be a String, Javabean or Collection/Map of either. Map<String, Object> data = new HashMap<String, Object>(); data.put("success", true); data.put("message", "Hello World!"); data.put("param", request.getParameter("foo")); // Write response data as JSON. response.setContentType("application/json"); response.setCharacterEncoding("UTF-8"); response.getWriter().write(new Gson().toJson(data)); } </code></pre> <p>Once the servlet is finished, just map it in <code>web.xml</code> the usual way. E.g. on an <code>url-pattern</code> of <code>/firstServlet</code>. </p> <p>Then, in jQuery you can use use <a href="http://api.jquery.com/jQuery.getJSON/" rel="nofollow noreferrer"><code>$.getJSON()</code></a> to obtain JSON from the given resource. The first argument is the URL, which is obviously <code>firstServlet</code>. The second argument is the callback function wherein you can work on the returned response data. I've passed the request parameter <code>foo</code> for pure demonstration purposes, this is not mandatory.</p> <pre><code>$.getJSON('firstServlet?foo=bar', function(data) { alert('Success: ' + data.success + '\n' + 'Message: ' + data.message + '\n' + 'Param: ' + data.param); }); </code></pre> <p>You can of course do more with this than just displaying a simple alert. E.g. manupulating/traversing the HTML DOM in the current page based on the returned data.</p> <p>I've posted two answers with practical examples before here, you may find it useful as well:</p> <ul> <li><a href="https://stackoverflow.com/questions/3028490/calling-a-java-servlet-from-javascript">calling a java servlet from javascript</a></li> <li><a href="https://stackoverflow.com/questions/2896730/how-to-generate-dynamic-drop-down-lists-using-jquery-and-jsp">How to generate dynamic drop down lists using jQuery and jsp?</a></li> </ul>

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