Hi, Guys!
Actually I want to ask about servlet and ajax.
Sorry if I post in wrong room, I have search the room that suitable for my question, but the most suitable is here.
I'm developing a push notification for web using servlet + ajax.
I have done an tutorial from this pages. Yes, it is working.
But my problem is how to modify the program to push message privately (for specific user).
I have searched it, but some tutorial suggest to use websocket. So, by using websocket, I must start from the beginning.
Do you have any suggestion to modify this program, so the server can send data to spesific user?
Do I must modify only in client (ajax) file or both of server (servlet) and client?
Thank you in advance.
This is the code:
/*
FileName: ShoutServlet.java
*/
package del10.if10048;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import javax.servlet.AsyncContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//import javax.servlet.AsyncListener;
import sun.org.mozilla.javascript.internal.Context;
import del10.if10048.MyAsyncListener;
@WebServlet(urlPatterns = {"/shoutServlet"}, asyncSupported = true)
public class ShoutServlet extends HttpServlet{
private List<AsyncContext> contexts = new LinkedList<>();
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
final AsyncContext asyncContext = request.startAsync(request, response);
asyncContext.setTimeout(10 * 60 * 1000);
contexts.add(asyncContext);
// attach listener to respond to lifecycle events of this AsyncContext
asyncContext.addListener(new MyAsyncListener());
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
List<AsyncContext> asyncContexts = new ArrayList<>(this.contexts);
this.contexts.clear();
String from = request.getParameter("from");
String to = request.getParameter("to");
String message = request.getParameter("message");
String htmlMessage = "<p><b>" + from + "</b><br/>" +"<i>" + to + "</i><br/>"+ message + "</p>";
ServletContext sc = request.getServletContext();
if (sc.getAttribute("messages") == null) {
sc.setAttribute("messages", htmlMessage);
} else {
String currentMessages = (String) sc.getAttribute("messages");
sc.setAttribute("messages", htmlMessage + currentMessages);
}
for (AsyncContext asyncContext : asyncContexts) {
try (PrintWriter writer = asyncContext.getResponse().getWriter()) {
writer.println(htmlMessage);
writer.flush();
asyncContext.complete();
} catch (Exception ex) {
}
}
response.sendRedirect("index.jsp");
}
}
and client side index.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!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>Insert title here</title>
</head>
<body>
<h1>SHOUT-OUT!</h1>
<!-- <form method="post" action="shoutServlet">-->
<form>
<table>
<tr>
<td>Your name:</td>
<td><input type="text" id="from" name="from"/></td>
</tr>
<tr>
<td>To whom:</td>
<td><input type="text" id="to" name="to"/></td>
</tr>
<tr>
<td>Your shout:</td>
<td><input type="text" id="message" name="message" /></td>
</tr>
<tr>
<td><input type="button" onclick="postMessage();" value="SHOUT" /></td>
<!--<td><input type="submit" value="SHOUT" /></td> -->
</tr>
</table>
</form>
<h2> Current Shouts </h2>
<div id="content">
<% if (application.getAttribute("messages") != null) {%>
<%= application.getAttribute("messages")%>
<% }%>
</div>
<script>
function postMessage() {
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("POST", "shoutServlet?u="+document.getElementById("to").value, true);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
var fromText = escape(document.getElementById("from").value);
var toText= escape(document.getElementById("to").value);
var messageText = escape(document.getElementById("message").value);
document.getElementById("message").value = "";
xmlhttp.send("from="+fromText+"&to="+toText+"&message="+messageText);
}
var messagesWaiting = false;
function getMessages(){
if(!messagesWaiting){
messagesWaiting = true;
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange=function(){
if (xmlhttp.readyState==4 && (xmlhttp.status==200||xmlhttp.status==500)) {
messagesWaiting = false;
var contentElement = document.getElementById("content");
contentElement.innerHTML = xmlhttp.responseText + contentElement.innerHTML;
}
}
xmlhttp.open("GET", "shoutServlet?t="+new Date(), true);
xmlhttp.send();
}
}
setInterval(getMessages, 1000);
</script>
</body>
</html>
