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dwr做comet的完整实现2008-07-05 来自：villa123  [收藏到我的网摘]

场景：页面comet.jsp接受服务器推送的信息并显示，页面action.jsp执行一个动作，调用DwrServer.perform方法，perform方法做某些事，并发送事件信息PerformInfo。NotifyClient监听事件，当接收到PerformInfo后，把PerformInfo的信息发送到comet.jsp页面。这个场景模拟了页面1执行了一个时间比较长或复杂的任务，任务执行情况可以反馈到页面2(比如模式窗口)。
信息载体PerformInfo.java
package application.comet;

import java.util.Date;

public class PerformInfo {
private int id;
private String msg;
private Date time;
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the msg
*/
public String getMsg() {
return msg;
}
/**
* @param msg the msg to set
*/
public void setMsg(String msg) {
this.msg = msg;
}
/**
* @return the time
*/
public Date getTime() {
return time;
}
/**
* @param time the time to set
*/
public void setTime(Date time) {
this.time = time;
}

}

package application.comet;

import java.util.Date;

public class PerformInfo {
private int id;
private String msg;
private Date time;
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the msg
*/
public String getMsg() {
return msg;
}
/**
* @param msg the msg to set
*/
public void setMsg(String msg) {
this.msg = msg;
}
/**
* @return the time
*/
public Date getTime() {
return time;
}
/**
* @param time the time to set
*/
public void setTime(Date time) {
this.time = time;
}

}
Spring的事件InfoEvent.java
package application.comet;

import org.springframework.context.ApplicationEvent;

public class InfoEvent extends ApplicationEvent {
public InfoEvent(Object source){
super(source);
}
}
DwrService.java 执行任务，就是写了100遍PerformInfo,需要实现ApplicationContextAware接口
package application.comet;

import java.util.Date;

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEvent;

public class DwrService implements ApplicationContextAware{
private ApplicationContext ctx;
public void setApplicationContext(ApplicationContext ctx) {
this.ctx = ctx;
}
public void perform(){
for (int i=0; i<100; i++){
PerformInfo info = new PerformInfo();
info.setId(i);
info.setMsg("发送"+i+"信息");
info.setTime(new Date());
InfoEvent evt = new InfoEvent(info);
ctx.publishEvent(evt);
}
}

}

NotifyClient.java监听事件，发送信息到页面。实现ApplicationListener,ServletContextAware接口，对中文需要编码
package application.comet;

import java.io.UnsupportedEncodingException;
import java.util.Collection;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import org.springframework.web.context.ServletContextAware;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;

public class NotifyClient implements ApplicationListener,ServletContextAware{
private ServletContext servletContext = null;
public void setServletContext( ServletContext servletContext )
{
this.servletContext = servletContext;
}

public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof InfoEvent) {
PerformInfo info = (PerformInfo)event.getSource();
System.out.println(info.getMsg());
//Collection sessions=ctx.getAllScriptSessions();
ServerContext ctx = ServerContextFactory.get(servletContext );
Collection sessions =
ctx.getScriptSessionsByPage("/dwrcomet/comet.jsp");
for (ScriptSession session : sessions) {
ScriptBuffer script = new ScriptBuffer();
String s=null;
String s2 = null;
try {
s = java.net.URLEncoder.encode(info.getMsg(),"UTF-8");
s2 = java.net.URLEncoder.encode("通知结束","UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
if (info.getId()<99){
script.appendScript("putInfo('")
.appendScript(info.getId()+":"+s)
.appendScript("'); ");
}else{
script.appendScript("alert(decodeURI('").
appendScript(s2).appendScript("')); ");
}

System.out.println(script.toString());
session.addScript(script);
}
}
}

}

action.jsp执行任务
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String root = request.getContextPath();
%>



















comet.jsp接受信息。关键是增加onload="dwr.engine.setActiveReverseAjax(true); ",还可以根据user或session id判断是否是自己的信息.
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String root = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"
+request.getServerPort()+root+"/";
%>























applicationContext.xml配置了NotifyClient和DwrService，这两个bean实现了ApplicationContextAware







dwr.xml

"-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN"
"http://www.getahead.ltd.uk/dwr/dwr10.dtd">









web.xml定义了dwr的comet控制，关键是pollAndCometEnabled=true

xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

contextConfigLocation
/WEB-INF/app*.xml


context

org.springframework.web.context.ContextLoaderServlet

1




dwr-invoker
org.directwebremoting.servlet.DwrServlet

debug
true


pollAndCometEnabled
true

1


dwr-invoker
/dwr/*



运行时要先打开comet.jsp,然后执行action.jsp

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场景：页面comet.jsp接受服务器推送的信息并显示，页面action.jsp执行一个动作，调用DwrServer.perform方法，perform方法做某些事，并发送事件信息PerformInfo。NotifyClient监听事件

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