关键字: Jetty, Cometd, Continuation, dojo
前言:
为了更容易的掌握Jetty cometd的使用方法,本笔记通过讲解Jetty 6.0自带的chat演示程序来辅助讲解Jetty Cometd的实现。
环境配置方法:
服务器端:
类库清单:WEB-INF/lib
jetty-6.1.9.jar
jetty-util-6.1.9.jar
servlet-api-2.5-6.1.9.jar
(以上Jetty服务器自带)
cometd-api-0.9.20080221.jar
cometd-bayeux-6.1.9.jar
web.xml配置:
< servlet >
< servlet-name > cometd </ servlet-name >
< servlet-class > org.mortbay.cometd.continuation.ContinuationCometdServlet </ servlet-class >
<!-- 对队列的内容进行过滤 -->
< init-param >
< param-name > filters </ param-name >
< param-value > /WEB-INF/filters.json </ param-value >
</ init-param >
<!-- 超时设置The server side poll timeout in milliseconds (default 250000). This is how long the server will
hold a reconnect request before responding. -->
< init-param >
< param-name > timeout </ param-name >
< param-value > 120000 </ param-value >
</ init-param >
<!-- The client side poll timeout in milliseconds (default 0). How long a client will wait between
reconnects -->
< init-param >
< param-name > interval </ param-name >
< param-value > 0 </ param-value >
</ init-param >
<!-- the client side poll timeout if multiple connections are detected from the same browser
(default 1500). -->
< init-param >
< param-name > multiFrameInterval </ param-name >
< param-value > 1500 </ param-value >
</ init-param >
<!-- 0=none, 1=info, 2=debug -->
< init-param >
< param-name > logLevel </ param-name >
< param-value > 0 </ param-value >
</ init-param >
<!-- If "true" then the server will accept JSON wrapped in a comment and will generate JSON wrapped
in a comment. This is a defence against Ajax Hijacking. -->
< init-param >
< param-name > JSONCommented </ param-name >
< param-value > true </ param-value >
</ init-param >
< init-param >
< param-name > alwaysResumePoll </ param-name >
< param-value > false </ param-value > <!-- use true for x-site cometd -->
</ init-param >
< load-on-startup > 1 </ load-on-startup >
</ servlet >
< servlet-mapping >
< servlet-name > cometd </ servlet-name >
< url-pattern > /cometd/* </ url-pattern >
</ servlet-mapping >
filters.json内容如下:
格式如下:
{
"channels": "/**", --要过滤的队列(支持通配符)
"filter":"org.mortbay.cometd.filter.NoMarkupFilter", --使用的过滤器,实现接口dojox.cometd.DataFilter
"init" : {} --初始化的值,调用 DataFilter.init方法传入
}
示例内容如下:
{
" channels " : " /** " ,
" filter " : " org.mortbay.cometd.filter.NoMarkupFilter " ,
" init " : {}
} ,
{
" channels " : " /chat/* " ,
" filter " : " org.mortbay.cometd.filter.RegexFilter " ,
" init " : [
[ "[fF ] .ck " , " dang " ],
[ " teh " , " the " ]
]
},
{
" channels " : " /chat/** " ,
" filter " : " org.mortbay.cometd.filter.RegexFilter " ,
" init " : [
[ " [ Mm ] icrosoft " , " Micro\\$oft " ],
[ " .*tomcat.* " , null ]
]
}
]
这时,服务器端的配置就已经完成的,基本的cometd功能就可以使用了。
客户端通过 dojox.cometd.init("http://127.0.0.2:8080/cometd");就可以进行连接。
代码开发:
接下来,我们要准备客户端(使用dojo来实现)
一共三个文件
index.html
chat.js
chat.css(不是必须)
下面来看一下这两个文件的内容(加入注释)
index.html
< head >
< title > Cometd chat </ title >
< script type ="text/javascript" src ="../dojo/dojo/dojo.js" ></ script > <!-- dojo类库 -->
< script type ="text/javascript" src ="../dojo/dojox/cometd.js.uncompressed.js" ></ script > <!-- dojo-cometd类库 -->
< script type ="text/javascript" src ="chat.js" ></ script > <!-- chat js文件,控制cometd的连接,消息的发送与接收 -->
< link rel ="stylesheet" type ="text/css" href ="chat.css" >
</ head >
< body >
< h1 > Cometd Chat </ h1 >
< div id ="chatroom" >
< div id ="chat" ></ div >
< div id ="input" >
< div id ="join" > <!-- 未登录时,显示的登录名和登录按钮 -->
Username: < input id ="username" type ="text" />
< input id ="joinB" class ="button" type ="submit" name ="join" value ="Join" />
</ div >
< div id ="joined" class ="hidden" > <!-- 登录后,显示的消息框和发送,退出按钮(默认为隐藏) -->
Chat: < input id ="phrase" type ="text" ></ input >
< input id ="sendB" class ="button" type ="submit" name ="join" value ="Send" />
< input id ="leaveB" class ="button" type ="submit" name ="join" value ="Leave" />
</ div >
</ div >
</ div >
</ body >
chat.js文件
2 dojo.require( " dojox.cometd " );
3 dojo.require( " dojox.cometd.timestamp " );
4
5 // 定义一个room类
6 var room = {
7 // 定义属性
8 _last: "" , // 最后发送消息的人员(如果不是本人,则显示为空)
9 _username: null , // 当前的用户名
10 _connected: true , // 当前的连接状态 true已经连接, false表示未连接
11 groupName: " whimsical " , // 组名(未知)
12
13 // 登录操作
14 join: function (name){
15
16 if (name == null || name.length == 0 ){
17 alert('Please enter a username ! ');
18 } else {
19
20 dojox.cometd.init(
new String(document.location).replace( / http:\ / \ / [ ^ \ / ] */ ,'').replace( / \ / examples\ / . * $ / ,'') + " /cometd " );
21 // dojox.cometd.init("http://127.0.0.2:8080/cometd");
22 this ._connected = true ;
23
24 this ._username = name;
25 dojo.byId('join').className = 'hidden';
26 dojo.byId('joined').className = '';
27 dojo.byId('phrase').focus();
28
29 // subscribe and join
30 dojox.cometd.startBatch();
31 dojox.cometd.subscribe( " /chat/demo " , room, " _chat " , { groupName: this .groupName});
32 dojox.cometd.publish( " /chat/demo " , {
33 user: room._username,
34 join: true ,
35 chat : room._username + " has joined "
36 }, { groupName: this .groupName });
37 dojox.cometd.endBatch();
38
39 // handle cometd failures while in the room
40 room._meta = dojo.subscribe( " /cometd/meta " , this , function (event){
41 console.debug(event);
42 if (event.action == " handshake " ){
43 room._chat({ data: {
44 join: true ,
45 user: " SERVER " ,
46 chat: " reinitialized "
47 } });
48 dojox.cometd.subscribe( " /chat/demo " , room, " _chat " , { groupName: this .groupName });
49 } else if (event.action == " connect " ){
50 if (event.successful && ! this ._connected){
51 room._chat({ data: {
52 leave: true ,
53 user: " SERVER " ,
54 chat: " reconnected! "
55 } });
56 }
57 if ( ! event.successful && this ._connected){
58 room._chat({ data: {
59 leave: true ,
60 user: " SERVER " ,
61 chat: " disconnected! "
62 } });
63 }
64 this ._connected = event.successful;
65 }
66 }, {groupName: this .groupName });
67 }
68 },
69
70 // 离开操作
71 leave: function (){
72 if ( ! room._username){
73 return ;
74 }
75
76 if (room._meta){
77 dojo.unsubscribe(room._meta, null , null , { groupName: this .groupName });
78 }
79 room._meta = null ;
80
81 dojox.cometd.startBatch();
82 dojox.cometd.unsubscribe( " /chat/demo " , room, " _chat " , { groupName: this .groupName });
83 dojox.cometd.publish( " /chat/demo " , {
84 user: room._username,
85 leave: true ,
86 chat : room._username + " has left "
87 }, { groupName: this .groupName });
88 dojox.cometd.endBatch();
89
90 // switch the input form
91 dojo.byId('join').className = '';
92 dojo.byId('joined').className = 'hidden';
93 dojo.byId('username').focus();
94 room._username = null ;
95 dojox.cometd.disconnect();
96 },
97
98 // 发送消息
99 chat: function (text){
100 if ( ! text || ! text.length){
101 return false ;
102 }
103 dojox.cometd.publish( " /chat/demo " , { user: room._username, chat: text}, { groupName: this .groupName });
104 },
105
106 // 从服务器收到消息后,回调的方法
107 _chat: function (message){
108 var chat = dojo.byId('chat');
109 if ( ! message.data){
110 console.debug( " bad message format " + message);
111 return ;
112 }
113 var from = message.data.user;
114 var special = message.data.join || message.data.leave;
115 var text = message.data.chat;
116 if ( ! text){ return ; }
117
118 if ( ! special && from == room._last ){
119 from = " " ;
120 } else {
121 room._last = from;
122 from += " : " ;
123 }
124
125 if (special){
126 chat.innerHTML += " <span class=\ " alert\ " ><span class=\ " from\ " > " + from + "
</span><span class=\ " text\ " > " + text + " </span></span><br/> " ;
127 room._last = "" ;
128 } else {
129 chat.innerHTML += " <span class=\ " from\ " > " + from + " </span><span class=\ " text\ " > " + text + " </span><br/> " ;
130 }
131 chat.scrollTop = chat.scrollHeight - chat.clientHeight;
132 },
133
134 // 初始操作
135 _init: function (){
136 dojo.byId('join').className = '';
137 dojo.byId('joined').className = 'hidden';
138 dojo.byId('username').focus();
139
140 var element = dojo.byId('username');
141 element.setAttribute( " autocomplete " , " OFF " );
142 dojo.connect(element, " onkeyup " , function (e){ // 支持回车,登录
143 if (e.keyCode == dojo.keys.ENTER){
144 room.join(dojo.byId('username').value);
145 return false ;
146 }
147 return true ;
148 });
149
150 dojo.connect(dojo.byId('joinB'), " onclick " , function (e){ // 绑定 room.join方法到 Join按扭
151 room.join(dojo.byId('username').value);
152 e.preventDefault();
153 });
154
155 element = dojo.byId('phrase'); // 取得消息框
156 element.setAttribute( " autocomplete " , " OFF " );
157 dojo.connect(element, " onkeyup " , function (e){ // 支持回车发送消息
158 if (e.keyCode == dojo.keys.ENTER){
159 room.chat(dojo.byId('phrase').value);
160 dojo.byId('phrase').value = '';
161 e.preventDefault();
162 }
163 });
164
165 dojo.connect(dojo.byId('sendB'), " onclick " , function (e){ // 绑定 room.chat方法到 sendB按扭
166 room.chat(dojo.byId('phrase').value);
167 dojo.byId('phrase').value = '';
168 });
169 dojo.connect(dojo.byId('leaveB'), " onclick " , room, " leave " ); // 绑定 room.leave方法到 leaveB按扭
170 }
171 };
172
173 // 页面装载时,调用room._init方法
174 dojo.addOnLoad(room, " _init " );
175 // 页面关闭时,调用 room.leave方法
176 dojo.addOnUnload(room, " leave " );
177
178 // vim:ts=4:noet:
补充:服务器端如何监控消息队列,以及进行订阅,发送消息操作
要进行 监控消息队列,以及进行订阅,发送消息操作的关键就是取得 Bayeux接口实现类 的实例
可以通过 ServletContextAttributeListener 这个监听器接口,通过attributeAdded方式加入
实现方法如下:
2 {
3 public void initialize(Bayeux bayeux)
4 {
5 synchronized (bayeux)
6 {
7 if ( ! bayeux.hasChannel( " /service/echo " ))
8 {
9 // 取得 bayeux实例
10 }
11 }
12 }
13
14 public void attributeAdded(ServletContextAttributeEvent scab)
15 {
16 if (scab.getName().equals(Bayeux.DOJOX_COMETD_BAYEUX))
17 {
18 Bayeux bayeux = (Bayeux) scab.getValue();
19 initialize(bayeux);
20 }
21 }
22
23 public void attributeRemoved(ServletContextAttributeEvent scab)
24 {
25
26 }
27
28 public void attributeReplaced(ServletContextAttributeEvent scab)
29 {
30
31 }
32 }
取到 Bayeux实例后,就可以借助BayeuxService类帮我们实现消息队列的监听,订阅消息以及发送消息
2 {
3 synchronized (bayeux)
4 {
5 if ( ! bayeux.hasChannel( " /service/echo " ))
6 {
7 // 取得 bayeux实例
8 new ChatService(bayeux);
9 }
10 }
11 }
具体方法请看下面这段代码:
2 public static class ChatService extends BayeuxService {
3
4 ConcurrentMap < String,Set < String >> _members = new ConcurrentHashMap < String,Set < String >> ();
5
6 public ChatService(Bayeux bayeux)
7 {
8 super (bayeux, " chat " ); // 必须,把 Bayeux传入到 BayeuxService对象中
9 subscribe( " /chat/** " , " trackMembers " ); // 订阅队列,收到消息后,会回调trackMembers方法
10 /*
11 subscribe支持回调的方法如下:
12 # myMethod(Client fromClient, Object data)
13 # myMethod(Client fromClient, Object data, String id)
14 # myMethod(Client fromClient, String channel, Object data,String id)
15 # myMethod(Client fromClient, Message message)
16
17 参数:
18 Client fromClient 发送消息的客户端
19 Object data 消息内容
20 id The id of the message
21 channel 队列名称
22 Message message 消息对象。继承于Map
23
24 */
25 }
26
27 // 发布消息到队列
28 public void sendMessage(String message) {
29 Map < String,Object > mydata = new HashMap < String, Object > ();
30 mydata.put( " chat " , message);
31
32 Client sender = getBayeux().newClient( " server " );
33
34 getBayeux().getChannel( " /chat/demo " , false ).publish(sender, mydata, " 0 " /* null */ );
35
36 }
37
38 // 发送消息给指定的client(非广播方式)
39 public void sendMessageToClient(Client joiner, String message) {
40 Map < String,Object > mydata = new HashMap < String, Object > ();
41 mydata.put( " chat " , message);
42
43 send(joiner, " /chat/demo " , mydata, " 0 " /* null */ );
44 }
45
46 // 订阅消息回调方法
47 public void trackMembers(Client joiner, String channel, Map < String,Object > data, String id)
48 {
49 // 解释消息内容,如果消息内容中 有 join这个字段且值为true
50 if (Boolean.TRUE.equals(data.get( " join " )))
51 {
52 // 根据队列,取得当前登录的人员
53 Set < String > m = _members.get(channel);
54 if (m == null )
55 {
56 // 如果为空,则创建一个新的Set实现
57 Set < String > new_list = new CopyOnWriteArraySet < String > ();
58 m = _members.putIfAbsent(channel,new_list);
59 if (m == null )
60 m = new_list;
61 }
62
63 final Set < String > members = m;
64 final String username = (String)data.get( " user " );
65
66 members.add(username);
67 // 为该client增加事件,Remove事件。当用户退出时,触发该方法。
68 joiner.addListener( new RemoveListener(){
69 public void removed(String clientId, boolean timeout)
70 {
71 members.remove(username);
72 }
73 });
74
75 // 为该client增加事件,消息的发送和接收事件。当用户退出时,触发该方法。
76 joiner.addListener( new MessageListener() {
77 public void deliver(Client fromClient, Client toClient, Message message) {
78 System.out.println( " message from " + fromClient.getId() + " to "
79 + toClient.getId() + " message is " + message.getData());
80 }
81 });
82
83 Map < String,Object > mydata = new HashMap < String, Object > ();
84 mydata.put( " chat " , " members= " + members);
85 // 把已经登录的人员信息列表,发送回给消息发送者
86 send(joiner,channel,mydata,id);
87
88 }
89 }
90 }
91
附:部分使用到的API文档
dojox.cometd.subscribe
dojox.cometd.subscribe()
handles all the hard work of telling the server that we want to be notified when events are published on a particular topic. subscribe
accepts a function to handle messages and returns a dojo.Deferred
object which has an extra property added to it which makes it suitable for passing to dojox.cometd.unsubscribe()
as a “subscription handle” (much like the handle object that dojo.connect()
produces and which dojo.disconnect()
expects).
Note that of a subscription is registered before a connection with the server is established, events sent before the connection is established will not be delivered to this client. The deferred object which subscribe
returns will callback when the server successfuly acknolwedges receipt of our “subscribe” request.
Usage
props = props||{}; if(objOrFunc){ var tname = "/cometd"+channel; var subs = this._subscriptions[tname]; if(!subs || subs.length==0){ subs = []; props.channel = "/meta/subscribe"; props.subscription = channel; this._sendMessage(props); var _ds = this._deferredSubscribes; if(_ds[channel]){ _ds[channel].cancel(); delete _ds[channel]; } _ds[channel] = new dojo.Deferred(); } for(var i in subs){ if( subs[i].objOrFunc === objOrFunc && (!subs[i].funcName&&!funcName||subs[i].funcName==funcName) ){ return null; } } var topic = dojo.subscribe(tname, objOrFunc, funcName); subs.push({ topic: topic, objOrFunc: objOrFunc, funcName: funcName }); this._subscriptions[tname] = subs; } var ret = this._deferredSubscribes[channel]||{}; ret.args = dojo._toArray(arguments); return ret; // dojo.Deferred
parameter | type | description |
---|---|---|
channel | String | |
objOrFunc | Object | an object scope for funcName or the name or reference to a function to be called when messages are delivered to the |
funcName | String | the second half of the objOrFunc/funcName pair for identifying a callback function to notifiy upon channel message delivery |
props | Object | Optional. |
Examples
Example 1
Simple subscribe use-case
dojox.cometd.init("http://myserver.com:8080/cometd");
// log out all incoming messages on /foo/bar
dojox.cometd.subscribe("/foo/bar", console, "debug");
Example 2
Subscribe before connection is initialized
dojox.cometd.subscribe("/foo/bar", console, "debug");
dojox.cometd.init("http://myserver.com:8080/cometd");
Example 3
Subscribe an unsubscribe
dojox.cometd.init("http://myserver.com:8080/cometd");
var h = dojox.cometd.subscribe("/foo/bar", console, "debug");
dojox.cometd.unsubscribe(h);
Example 4
Listen for successful subscription:
dojox.cometd.init("http://myserver.com:8080/cometd");
var h = dojox.cometd.subscribe("/foo/bar", console, "debug");
h.addCallback(function(){
console.debug("subscription to /foo/bar established");
});
dojox.cometd.publish
Usage
var message = { data: data, channel: channel }; if(props){ dojo.mixin(message, props); } this._sendMessage(message);
parameter | type | description |
---|---|---|
channel | String | the destination channel for the message |
data | Object | a JSON object containing the message "payload" properties: Optional. Other meta-data to be mixed into the top-level of the message |
props | Object | Optional. |
Good Luck!
Yours Matthew!