I am trying
to implement a solution for a long running process on the server where it is taking about 10 min
to process a pdf generation request. The browser bored/timesout at the 5 mins. I was thinking
to deal with this using a
Ajax and threads. I am using regular javascript for
ajax. But I am stuck with it.
I have reached till the point where it sends the request
to the servlet and the servlet starts the thread.Please see the below code
public class HelloServlet extends javax.servlet.http.HttpServlet
implements javax.servlet.Servlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("POST request!!");
LongProcess longProcess = new LongProcess();
longProcess.setDaemon(true);
longProcess.start();
request.getSession().setAttribute("longProcess", longProcess);
request.getRequestDispatcher("index.jsp").forward(request, response);
}
}
class LongProcess extends Thread {
public void run() {
System.out.println("Thread Started!!");
while (progress < 10) {
try { sleep(2000); } catch (InterruptedException ignore) {}
progress++;
}
}
}
Here is my
AJax call
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>My Title</title>
<script language="JavaScript" >
function getXMLObject() //XML OBJECT
{
var xmlHttp = false;
xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers
return xmlHttp; // Mandatory Statement returning the
ajax object created
}
var xmlhttp = new getXMLObject(); //xmlhttp holds the
ajax object
function ajaxFunction() {
xmlhttp.open("GET","HelloServlet" ,true);
xmlhttp.onreadystatechange = handleServerResponse;
xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlhttp.send(null);
}
function handleServerResponse() {
if (xmlhttp.readyState == 4) {
if(xmlhttp.status == 200) {
document.forms[0].myDiv.value = xmlhttp.responseText;
setTimeout(ajaxFunction(), 2000);
}
else {
alert("Error during
AJAX call. Please try again");
}
}
}
function openPDF() {
document.forms[0].method = "POST";
document.forms[0].action = "HelloServlet";
document.forms[0].submit();
}
function stopAjax(){
clearInterval(intervalID);
}
</script>
</head>
<body><form name="myForm">
<table><tr><td>
<INPUT TYPE="BUTTON" NAME="Download" VALUE="Download Queue ( PDF )" onclick="openPDF();">
</td></tr>
<tr><td>
Current status: <div id="myDiv"></div>%
</td></tr></table>
</form></body></html>
But I dont know
how to proceed further like
how will the thread communicate the browser that the process has complete and
how should the
ajax call me made and check the status of the request.
Please let me know if I am missing some pieces. Any suggestion if helpful.
