dwr做comet的完整实现

dwr做comet的完整实现

   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<ScriptSession> sessions=ctx.getAllScriptSessions();
      ServerContext ctx  =  ServerContextFactory.get(servletContext );
      Collection < ScriptSession >  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();
%>

<! DOCTYPE HTML PUBLIC  " -//W3C//DTD HTML 4.01 Transitional//EN " >
< html >
   < head >
     < title > doing </ title >
    
     < meta http - equiv = " pragma "  content = " no-cache " >
     < meta http - equiv = " cache-control "  content = " no-cache " >
     < meta http - equiv = " expires "  content = " 0 " >     
< script type = ' text/javascript '  src = ' <%=root%>/dwr/engine.js ' ></ script >
< script type = ' text/javascript '  src = ' <%=root%>/dwr/util.js ' ></ script >
< script type = ' text/javascript '  src = ' <%=root%>/dwr/interface/DwrService.js ' ></ script >
   </ head >
  
   < body >
   < input name = ' action '  onclick = ' DwrService.perform(); '  type = " button "  value = " 行动 " />
   </ body >
</ html >

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 + " / " ;
%>

<! DOCTYPE HTML PUBLIC  " -//W3C//DTD HTML 4.01 Transitional//EN " >
< html >
   < head >
     < base href = " <%=basePath%> " >
    
     < title > Comet with DWR </ title >
    
     < meta http - equiv = " pragma "  content = " no-cache " >
     < meta http - equiv = " cache-control "  content = " no-cache " >
     < meta http - equiv = " expires "  content = " 0 " >     
   </ head >
  
< body onload = " dwr.engine.setActiveReverseAjax(true); " >
< script type = ' text/javascript '  src = ' <%=root%>/dwr/engine.js ' ></ script >
< script type = ' text/javascript '  src = ' <%=root%>/dwr/util.js ' ></ script >
< script type = " text/javascript " >
    var user  =   ' <%=request.getParameter("user")%> ' ;
    
    function putInfo(data) {
       var d  =  decodeURI(data);
       var text  =  dwr.util.getValue( ' info ' );       
       dwr.util.setValue( ' info ' ,text + ' \n ' + d);
    }
</ script >
< br />
< textarea rows = " 20 "  cols = " 100 "  id = ' info ' ></ textarea >
</ body >
</ html >

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

<? xml version="1.0" encoding="UTF-8" ?>
<! DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >
< beans >
   < bean  id ="notifyClient"  class ="application.comet.NotifyClient" >
   </ bean >
   < bean  id ="dwrService"  class ="application.comet.DwrService" ></ bean >
</ beans >

dwr.xml

<? xml version="1.0" encoding="UTF-8" ?>
<! DOCTYPE dwr PUBLIC
    "-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN"
    "http://www.getahead.ltd.uk/dwr/dwr10.dtd" >
< dwr >
   < allow >
     < create  creator ="spring"  javascript ="DwrService" >
       < param  name ="beanName"  value ="dwrService"   />
     </ create >
   </ allow >
</ dwr >

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

<? xml version="1.0" encoding="UTF-8" ?>
< web-app  version ="2.4"  
    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" >
     < context-param >
         < param-name > contextConfigLocation </ param-name >
         < param-value > /WEB-INF/app*.xml </ param-value >
     </ context-param >
     < servlet >
         < servlet-name > context </ servlet-name >
         < servlet-class >
            org.springframework.web.context.ContextLoaderServlet
         </ servlet-class >
         < load-on-startup > 1 </ load-on-startup >
     </ servlet >

  <!-- dwr servlet -->
   < servlet >
     < servlet-name > dwr-invoker </ servlet-name >
     < servlet-class > org.directwebremoting.servlet.DwrServlet </ servlet-class >
     < init-param >
         < param-name > debug </ param-name >
         < param-value > true </ param-value >
     </ init-param >
     < init-param >
       < param-name > pollAndCometEnabled </ param-name >
       < param-value > true </ param-value >
     </ init-param >
     < load-on-startup > 1 </ load-on-startup >       
   </ servlet >
   < servlet-mapping >
       < servlet-name > dwr-invoker </ servlet-name >
       < url-pattern > /dwr/* </ url-pattern >
   </ servlet-mapping >
</ web-app >

运行时要先打开comet.jsp,然后执行action.jsp