使用Comet4j实现消息推送
Comet4J(Comet for Java)是一个纯粹基于AJAX(XMLHTTPRequest)的服务器推送框架，消息以JSON方式传递，具备长轮询、长连接、自动选择三种工作模式。有关comet4j更多的信息在此不再详细展开，需要了解的请访问地址 http://code.google.com/p/comet4j/。
在项目中使用comet4j需要引入2个文件，comet4j.js、comet4j-tomcat6.jar。下面是一个示例，希望对需要的人有所帮助。不足之处还请大神谅解。
view：hello.jsp
service code：NewMsgCollector.java
web.xml
在项目中使用comet4j需要引入2个文件，comet4j.js、comet4j-tomcat6.jar。下面是一个示例，希望对需要的人有所帮助。不足之处还请大神谅解。
view：hello.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>comet</title>
<script type="text/javascript" src="/comet4j_demo/js/jquery-1.8.0.min.js"></script>
<script type="text/javascript" src="/comet4j_demo/js/comet4j.js"></script>
<script type="text/javascript">
$(function(){
JS.Engine.on('hello', function(text){
$("#targetDiv").append("<span id='msgSpan' style='color:red'>" + text + "</span>");
});
<%
String userId = request.getParameter("userId");
session.setAttribute("currentUserId", userId);
%>
JS.Engine.start('conn');
});
$(document).ready(function(){
$("#targetDiv").bind("click", function(){
//有新消息
if ($(this).find("span").length > 0) {
$("div > span").remove();
}
});
});
</script>
</head>
<body>
<table border="1" width:600px>
<tr>
<td>hello comet</td>
<td><div id="targetDiv" style="width:300px"></div></td>
</tr>
</table>
</body>
</html>
service code：NewMsgCollector.java
public class NewMsgCollector extends ConnectListener implements ServletContextListener {
private static final String CHANNEL = "hello";
@Override
public void contextInitialized(ServletContextEvent contextEvent) {
//注册应用的channel
CometContext context = CometContext.getInstance();
context.registChannel(CHANNEL);
//添加监听器
CometEngine engine = CometContext.getInstance().getEngine();
engine.addConnectListener(this);
}
@Override
public void contextDestroyed(ServletContextEvent contextEvent) {}
@Override
public boolean handleEvent(ConnectEvent connEvent) {
final CometConnection conn = connEvent.getConn();
//建立连接和用户的关系
doCache(conn);
final String connId = conn.getId();
/*模拟业务逻辑*/
Timer timer = new Timer(true);
TimerTask task = new TimerTask() {
@Override
public void run() {
CometEngine engine = CometContext.getInstance().getEngine();
//推送到所有客户端
//engine.sendToAll("hello", connId + " - you have " + ((int)(Math.random() * 9) + 1) + " new message <br />");
if (CacheManager.getContent(connId).isExpired()) {
doCache(conn);
}
if (simulateService(String.valueOf(CacheManager.getContent(connId).getValue()))) {
//推送到指定的客户端
engine.sendTo(CHANNEL, engine.getConnection(connId), CacheManager.getContent(connId).getValue()
+ " - you have " + ((int) (Math.random() * 9) + 1) + " new message <br />");
}
}
};
timer.schedule(task, 10000, (1000 * 5));
return true;
}
private void doCache(final CometConnection conn) {
Object userId = conn.getRequest().getSession().getAttribute("currentUserId");
if (userId != null) {
CacheManager.putContent(conn.getId(), String.valueOf(userId), CacheConstant.EXPIRE_AFTER_ONE_HOUR);
}
}
/**
* 模拟业务
* 返回true,false
* true即表示需要推送消息,false即不需要推送
*/
private boolean simulateService(String id) {
int flag = (int) Math.round(Math.random());
if (flag == 0) {
System.out.println(id + " - no messge...");
return false;
}
System.out.println(id + " - messge is coming...");
return true;
}
}
web.xml
<listener> <description>Comet4J容器侦听</description> <listener-class>org.comet4j.core.CometAppListener</listener-class> </listener> <servlet> <description>Comet连接[默认:org.comet4j.core.CometServlet]</description> <display-name>CometServlet</display-name> <servlet-name>CometServlet</servlet-name> <servlet-class>org.comet4j.core.CometServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CometServlet</servlet-name> <url-pattern>/conn</url-pattern> </servlet-mapping> <listener> <description>NewMsgCollector</description> <listener-class>NewMsgCollector</listener-class> </listener>