DWR3-ReverseAjax-半推实现

第一次发帖，直奔主题。

 

首先，配置web.xml加入参数开启ReverseAjax

<servlet>
		<servlet-name>dwr</servlet-name>
		<servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
		<init-param>
			<param-name>activeReverseAjaxEnabled</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
		    <param-name>initApplicationScopeCreatorsAtStartup</param-name>
		    <param-value>true</param-value>
	  	</init-param>
	  	<init-param>
			<param-name>org.directwebremoting.extend.ScriptSessionManager</param-name>
			<param-value>com.cssweb.business.dwr.CustomSSManager</param-value>
		</init-param>
	  	<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>dwr</servlet-name>
		<url-pattern>/dwr/*</url-pattern>
	</servlet-mapping>

   注意红色部分，即半推实现方式：加入自己的ScriptSessionManager.由于dwr每次刷新激活ReverseAjax的页面都会创建一个ScriptSession，这里要自己管理它以便实现半推，同时和HttpSession做同步，以最后请求的ScriptSession为准，销毁之前的ScriptSession。

下面就是CustomSSManager：

import java.util.Collection;

import javax.servlet.http.HttpSession;

import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;
import org.directwebremoting.impl.DefaultScriptSession;
import org.directwebremoting.impl.DefaultScriptSessionManager;

import com.cssweb.business.user.pojo.User;
import com.cssweb.constans.CONST;

/**
 * 
 * 扩展ScriptSessionManager.
 * @author congyy
 * @createTime   2010-1-3           
 */
public class CustomSSManager extends DefaultScriptSessionManager {
        public static final String SS_ID = "DWR_ScriptSession_Id";
        public CustomSSManager() {
             addScriptSessionListener(new ScriptSessionListener(){
                public void sessionCreated(ScriptSessionEvent event) {
                        ScriptSession scriptSession = event.getSession(); // 获取新创建的SS
                        HttpSession httpSession  = WebContextFactory.get().getSession();// 获取构造SS的用户的HttpSession
                        User user = (User)httpSession.getAttribute(CONST.SESSION_USER);
                        if(user ==null){
                                scriptSession.invalidate();
                                httpSession.invalidate();
                                return;
                        }
                        String ssId = (String) httpSession.getAttribute(SS_ID);
                        if (ssId != null) {
                                DefaultScriptSession old=sessionMap.get(ssId);
                               if(old!=null)CustomSSManager.this.invalidate(old);
                        }
                        httpSession.setAttribute(SS_ID, scriptSession.getId());
                        scriptSession.setAttribute("userId", user.getId());//此处将userId和scriptSession绑定
                }
                public void sessionDestroyed(ScriptSessionEvent event) {}
             });
           ReqReverseAjax.manager=this;//将自己暴露ReverseAjax业务处理类

        }
        public Collection getAllScriptSessions(){
                return sessionMap.values();
        }
}

 关于上述代码 ：User为POJO类，CONST为常量放置接口,如session中的用户KEY.

 然后是ReverseAjax业务处理类：

package com.cssweb.business.dwr;

import java.util.Collection;
import java.util.Observable;
import java.util.Observer;

import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.extend.ScriptSessionManager;

import com.cssweb.business.user.pojo.UserReq;
import com.cssweb.business.user.service.IUserReqService;


/**
 * Observer实现，监听事件，然后推送给指定用户.
 */
public class ReqReverseAjax implements Observer{
  static ScriptSessionManager manager ;
  public ReqReverseAjax() {
          IUserReqService.GCZ.addObserver(this);//注册观察者
  }
  public void update(Observable o, Object arg) {
        final UserReq req = (UserReq) arg;
        final Long userId = req.getToId();//获取事件要通知的用户的id
        Collection<ScriptSession>  coll = manager.getAllScriptSessions();//获取当前所有ScriptSession
        for(ScriptSession ss : coll) {
             if(ss.getAttribute("userId").equals(userId)){
                     ss.addScript(new ScriptBuffer().appendScript("update").appendScript("(").appendData(req).appendScript(");"));//找到符合要求的，推送事件
                     break;
             }
        }
   }
}

 然后在WEB-INF/下丢一个dwr.xml：

 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" "http://getahead.org/dwr/dwr30.dtd">
<dwr>
  <allow>
    <create creator="new" scope="application">
      	<param name="class" value="com.cssweb.business.dwr.ReqReverseAjax"/>
    </create>
    <convert converter="bean" match="com.cssweb.business.user.pojo.UserReq"/>
  </allow>
</dwr>

 至此，服务端配置完全结束，实现半推。

 页面上实现如下：

  index.jsp，加上框架，减少对reverseAjax.html页面的刷新量

<%@ page  pageEncoding="UTF-8"%>
<frameset rows="*" cols="0,*" border="0">
	<frame src="${contextPath }/jsp/ajax/user/reverseAjax.html#${contextPath }" frameborder="0">
	<frame src="${contextPath }/jsp/user/index.do"/>
</frameset>

 

reverseAjax.html:

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript">
	 function update(req) {
	 	//在这里处理服务器推过来的信息
	 }
	 var url = self.location.href;
	 var ctx = url.slice(url.indexOf('#')+1);
	 document.write("<script src='"+ctx+"/dwr/engine.js'><\/script>"); 
</script>
</head>
<body οnlοad="dwr.engine.setActiveReverseAjax(true)">
</body>
</html>

 好了，至此半推结束.