1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
//
// ========================================================================
// Copyright (c) 1995-2012 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package com.acme;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.eclipse.jetty.continuation.Continuation;
import org.eclipse.jetty.continuation.ContinuationSupport;
// Simple asynchronous Chat room.
// This does not handle duplicate usernames or multiple frames/tabs from the same browser
// Some code is duplicated for clarity.
public class ChatServlet extends HttpServlet
{
// inner class to hold message queue for each chat room member
class Member
{
String _name;
Continuation _continuation;
Queue<String> _queue = new LinkedList<String>();
}
Map<String,Map<String,Member>> _rooms = new HashMap<String,Map<String, Member>>();
// Handle Ajax calls from browser
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// Ajax calls are form encoded
String action = request.getParameter("action");
String message = request.getParameter("message");
String username = request.getParameter("user");
if (action.equals("join"))
join(request,response,username);
else if (action.equals("poll"))
poll(request,response,username);
else if (action.equals("chat"))
chat(request,response,username,message);
}
private synchronized void join(HttpServletRequest request,HttpServletResponse response,String username)
throws IOException
{
Member member = new Member();
member._name=username;
Map<String,Member> room=_rooms.get(request.getPathInfo());
if (room==null)
{
room=new HashMap<String,Member>();
_rooms.put(request.getPathInfo(),room);
}
room.put(username,member);
response.setContentType("text/json;charset=utf-8");
PrintWriter out=response.getWriter();
out.print("{action:\"join\"}");
}
private synchronized void poll(HttpServletRequest request,HttpServletResponse response,String username)
throws IOException
{
Map<String,Member> room=_rooms.get(request.getPathInfo());
if (room==null)
{
response.sendError(503);
return;
}
Member member = room.get(username);
if (member==null)
{
response.sendError(503);
return;
}
synchronized(member)
{
if (member._queue.size()>0)
{
// Send one chat message
response.setContentType("text/json;charset=utf-8");
StringBuilder buf=new StringBuilder();
buf.append("{\"action\":\"poll\",");
buf.append("\"from\":\"");
buf.append(member._queue.poll());
buf.append("\",");
String message = member._queue.poll();
int quote=message.indexOf('"');
while (quote>=0)
{
message=message.substring(0,quote)+'\\'+message.substring(quote);
quote=message.indexOf('"',quote+2);
}
buf.append("\"chat\":\"");
buf.append(message);
buf.append("\"}");
byte[] bytes = buf.toString().getBytes("utf-8");
response.setContentLength(bytes.length);
response.getOutputStream().write(bytes);
}
else
{
Continuation continuation = ContinuationSupport.getContinuation(request);
if (continuation.isInitial())
{
// No chat in queue, so suspend and wait for timeout or chat
continuation.setTimeout(20000);
continuation.suspend();
member._continuation=continuation;
}
else
{
// Timeout so send empty response
response.setContentType("text/json;charset=utf-8");
PrintWriter out=response.getWriter();
out.print("{action:\"poll\"}");
}
}
}
}
private synchronized void chat(HttpServletRequest request,HttpServletResponse response,String username,String message)
throws IOException
{
Map<String,Member> room=_rooms.get(request.getPathInfo());
if (room!=null)
{
// Post chat to all members
for (Member m:room.values())
{
synchronized (m)
{
m._queue.add(username); // from
m._queue.add(message); // chat
// wakeup member if polling
if (m._continuation!=null)
{
m._continuation.resume();
m._continuation=null;
}
}
}
}
response.setContentType("text/json;charset=utf-8");
PrintWriter out=response.getWriter();
out.print("{action:\"chat\"}");
}
// Serve the HTML with embedded CSS and Javascript.
// This should be static content and should use real JS libraries.
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
if (request.getParameter("action")!=null)
doPost(request,response);
else
getServletContext().getNamedDispatcher("default").forward(request,response);
}
}
|
