DWR3.0框架入门 —— java页面推送

DWR3.0可以通过

//得到所有ScriptSession
Collection<ScriptSession> sessions = browser.getTargetSessions();

DWR2.x可以通过

Collection pages = webContext.getScriptSessionsByPage("/yourPage.jsp");

package sugar.dwr;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpSession;

import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;

public class DWRScriptSessionListener implements ScriptSessionListener {
     
     //维护一个Map key为session的Id， value为ScriptSession对象
     public static final Map<String,ScriptSession> scriptSessionMap = new HashMap<String,ScriptSession>();

     /**
      * ScriptSession创建事件
      */
     public void sessionCreated(ScriptSessionEvent event) {
           WebContext webContext = WebContextFactory. get();
           HttpSession session = webContext.getSession();
           ScriptSession scriptSession = event.getSession();
            scriptSessionMap.put(session.getId(),scriptSession);     //添加scriptSession
           System. out.println( "session: " + session.getId() + " scriptSession: " + scriptSession.getId() + "is created!");
     }

     /**
      * ScriptSession销毁事件
      */
     public void sessionDestroyed(ScriptSessionEvent event) {
           WebContext webContext = WebContextFactory. get();
           HttpSession session = webContext.getSession();
           ScriptSession scriptSession = scriptSessionMap.remove(session.getId());  //移除scriptSession
           System. out.println( "session: " + session.getId() + " scriptSession: " + scriptSession.getId() + "is destroyed!");
     }
     
     /**
      * 获取所有ScriptSession
      */
     public static Collection<ScriptSession> getScriptSessions(){
            return scriptSessionMap.values();
     }
}

2.新建一个类继承
DefaultScriptSessionManager，用来绑定
DWRScriptSessionListener

package sugar.dwr;

import org.directwebremoting.impl.DefaultScriptSessionManager;

public class DWRScriptSessionManager extends DefaultScriptSessionManager {
     public DWRScriptSessionManager(){
            //绑定一个ScriptSession增加销毁事件的监听器
            this.addScriptSessionListener( new DWRScriptSessionListener());
           System. out.println( "bind DWRScriptSessionListener");
     }
}

3.在web.xml中将
DWRScriptSessionManager
配置在
dwr-invoker servlet中

<init-param>
      <param-name >org.directwebremoting.extend.ScriptSessionManager </param-name>
      <param-value >sugar.dwr.DWRScriptSessionManager </param-value>
</init-param>

//得到所有ScriptSession
Collection<ScriptSession> sessions = DWRScriptSessionListener.getScriptSessions();

//执行推送
browser.withAllSessionsFiltered(filter,run);    //注意这里调用了有filter功能的方法

2.通过参数可知我们需要一个
ScriptSessionFilter对象，此时send的方法改写成如下：

public void send(final String content){
           
            //过滤器
           ScriptSessionFilter filter = new ScriptSessionFilter() {
                
                 public boolean match(ScriptSession scriptSession) {
                     String tag = (String)scriptSession.getAttribute("tag" );
                     System. out.println(tag);
                      return "receiverTag" .equals(tag);
                }
           };

           Runnable run = new Runnable(){
                 private ScriptBuffer script = new ScriptBuffer();
                 public void run() {
                      //设置要调用的 js及参数
                      script.appendCall( "show",content);
                      //得到所有ScriptSession
                     Collection<ScriptSession> sessions = DWRScriptSessionListener.getScriptSessions();
                      //遍历每一个ScriptSession
                      for (ScriptSession scriptSession : sessions){
                           scriptSession.addScript( script);
                     }
                }
           };
            //执行推送
           browser. withAllSessionsFiltered(filter,run);    //注意这里调用了有filter功能的方法
}

3.在打开jsp页面时需要在
ScriptSession
中注入设定的attribute，MessagePush中的方法

public void onPageLoad(final String tag){
        //获取当前的ScriptSession
        ScriptSession scriptSession = WebContextFactory.get().getScriptSession();
        scriptSession.setAttribute( "tag",tag);
        System. out.println( "setAttribute");
}

4.在jsp中调用该方法

<script type= "text/javascript">
         //这个方法用来启动该页面的ReverseAjax功能
         dwr.engine.setActiveReverseAjax( true);
         //设置在页面关闭时，通知服务端销毁会话
         dwr.engine.setNotifyServerOnPageUnload( true);
        
         var tag = "receiverTag";    //自定义一个标签
         messagePush.onPageLoad(tag);
        
         //这个函数是提供给后台推送的时候 调用的
         function show(content){ 
             $( "#content").text(content);
         }     
</script >

这样我们可以给不同客户端的jsp中导入不同的tag值，过滤推送的客户端