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POReturn JSON from servlet
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  1. POReturn JSON from servlet
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    copied!<p>It is a very basic request-response test. Browser sends "hello from browser" to servlet using jQuery $.ajax API, and servlet receives this message, then create a JSON object using org.json.simple library and sends back to browser a JSON response with message "hello from server".</p> <p>I am running this on localhost and just assume my IP address is 123.123.12.123, the platform is Ubuntu, server is Tomcat 6.0, running in the Eclipse IDE.</p> <p>Test 1. I start the server from Eclipse, open Firefox, enter <a href="http://localhost:8080/myproject/test.jsp" rel="nofollow noreferrer">http://localhost:8080/myproject/test.jsp</a>, I can see servlet receives message and browser receives response, test passed.</p> <p>Test 2. server is still running at the Eclipse at Ubuntu, I start Windows 7 guest machine from VirtualBox and the Firefox browser in the Windows 7, enter <a href="http://123.123.12.123:8080/myproject/test.jsp" rel="nofollow noreferrer">http://123.123.12.123:8080/myproject/test.jsp</a>, works as I expected, test passed.</p> <p>Test 3. server is still running at Eclipse at Ubuntu, open Internet Explorer 9 browser, give it address <a href="http://123.123.12.123:8080/myproject/test.jsp" rel="nofollow noreferrer">http://123.123.12.123:8080/myproject/test.jsp</a>, <b>nothing happens.</b> The debug gives me </p> <p>Response HTTP/1.1 200 OK</p> <p>Response body {"message":"hello from server"}</p> <p>The test.jsp is</p> <pre> &lt;%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%&gt; &lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"&gt; &lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8"&gt; &lt;title&gt;Insert title here&lt;/title&gt; &lt;/head&gt; &lt;script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.js" type="text/javascript"&gt;&lt;/script&gt; &lt;script type="text/javascript" src="release/js/libs/json2.js"&gt;&lt;/script&gt; &lt;script&gt; $(document).ready(function(){ var request = ({"message":'Hello from browser'}); var jsonobj=JSON.stringify(request); $.ajax({ data: {para:jsonobj}, dataType: 'json', url: './TestServlet', type: 'POST', success: function(jsonObj){ alert(jsonObj.message); }, error: function() { alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err); } }); }); &lt;/script&gt; &lt;body&gt; &lt;/body&gt; &lt;/html&gt; </pre> <p>The servlet code is</p> <pre> import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.json.simple.JSONObject; import org.json.simple.JSONValue; /** * Servlet implementation class TestServlet */ public class TestServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public TestServlet() { super(); } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf8"); response.setCharacterEncoding("utf8"); response.setContentType("application/json"); PrintWriter out = response.getWriter(); JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para")); System.out.println(jsonObj.get("message")); JSONObject obj = new JSONObject(); obj.put("message", "hello from server"); out.print(obj); } } </pre> <p>Update: </p> <p>After a closer look by change </p> <pre> error: function() { alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err); } </pre> <p>to</p> <pre> error: function(xhr,err) { alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err); } </pre> <p>I got alert readyState:0 and status:0. But I can see {"message":"hello from server"} at Response body and the response header is</p> <pre> Key Value Response HTTP/1.1 200 OK </pre>
 

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