dwr進行消息推送示例

<?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" javascript="PushMessage">
    <param name="class" value="com.manhui.push.controller.PushMessage"/>
    </create>          
  </allow>
</dwr>

　　

關於dwr的介紹可自行度娘，這裏主要作一個dwr進行消息推送的demo

第一步：這裏使用maven項目，先引入jar的倉庫地址：

1 <dependency>
2             <groupId>org.directwebremoting</groupId>
3             <artifactId>dwr</artifactId>
4             <version>3.0.0-RELEASE</version>
5         </dependency>

View Code

第二步：web.xml配置

	<!-- dwr相關配置 -->
	<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>logLevel</param-name>
			<param-value>WARN</param-value>
		</init-param>
		<init-param>
			<param-name>crossDomainSessionSecurity</param-name>
			<param-value>false</param-value>
		</init-param>
		<init-param>
			<param-name>allowScriptTagRemoting</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>classes</param-name>
			<param-value>java.lang.Object</param-value>
		</init-param>
		<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>maxWaitAfterWrite</param-name>
			<param-value>6000</param-value>
		</init-param>
		<load-on-startup>2</load-on-startup>  
	</servlet>
      <servlet-mapping>    
     <servlet-name>dwr-invoker</servlet-name>    
     <url-pattern>/dwr/*</url-pattern>    
  </servlet-mapping> 

　　第三步：後臺編碼

package com.manhui.push.controller;

import java.util.Collection;

import org.apache.log4j.Logger;
import org.directwebremoting.Browser;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessionFilter;
import org.directwebremoting.WebContextFactory;

/**
 * 推送消息控制層,這裏主要是進行消息的精確推送，固然若是要進行全部推送，則不須要進行過濾處理便可
 * @author hq
 *
 */
public class PushMessage {
	
	private Logger log = Logger.getLogger(PushMessage.class);
	
	 // 載入頁面時調用，傳入name值做爲推送的標識
    public void onPageLoad(String name) {
        ScriptSession session = WebContextFactory.get().getScriptSession();
        session.setAttribute("name", name);
    }
    public void addMessage(String userid, String message) {
        final String userId = userid;
        final String autoMessage = message;
        ScriptSession session = WebContextFactory.get().getScriptSession();
        String from =(String) session.getAttribute("name");
        
        // 獲取全部scriptsession並經過ScriptSessionFilter篩選符合條件的ScriptSession
        Browser.withAllSessionsFiltered(new ScriptSessionFilter() {
            // 實現match方法，條件爲真爲篩選出來的session
            public boolean match(ScriptSession session) {
                String name = session.getAttribute("name").toString();
               return name == null ? false : userId.equals(name);
            }
        }, new Runnable() {
            private ScriptBuffer script = new ScriptBuffer();
            public void run() {
                // 設定前臺接受消息的方法和參數
                script.appendCall("receiveMessages", autoMessage);
                Collection<ScriptSession> sessions = Browser
                        .getTargetSessions();//獲取有效的scriptsession
                // 向全部符合條件的頁面推送消息
                for (ScriptSession scriptSession : sessions) {
                    if (scriptSession.getAttribute("name").equals(userId)) {
                        scriptSession.addScript(script);
                    }
                }
            }
        });
    }
	
	

}

　　第四步：在web.xml同級目錄下建立dwr.xml文件

 

<?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" javascript="PushMessage">
    <param name="class" value="com.manhui.push.controller.PushMessage"/>
    </create>          
  </allow>
</dwr>

　　

第五步：在須要推送消息的頁面引入相關js,並在頁面初始化以前加載相關方法

   <script type="text/javascript" src="dwr/engine.js"></script>
   <script type="text/javascript" src="dwr/util.js"></script>
   <script type="text/javascript" src="dwr/interface/PushMessage.js"></script>

　　   <script type="text/javascript" src="dwr/interface/PushMessage.js"></script>該js文件是根據dwr.xml自行生成的，前面的是dwr.jar裏面的

頁面初始化加載調用：

  dwr.engine.setActiveReverseAjax(true);// 開啓逆向Ajax，也可寫在body標籤的onload方法中
  dwr.engine.setNotifyServerOnPageUnload(true);
  dwr.engine.setErrorHandler(function(){});//"   這個方法 防止項目已經關閉，客戶頁面還未關閉，頁面會談Error的問題
  onPageLoad();

　　

var chatlog = "";
var name = '${name}';
function sendMessage() {
    var message = $("#message").val();
    var user = $("#user").val();
    // 經過代理調用後臺的addMessage方法發送消息
    PushMessage.addMessage(user, message);
}

// 前臺接受消息的方法，由後臺調用 
function receiveMessages(messages) {
    var lastMessage =  messages;
    chatlog = "<p>" + lastMessage + "</p>" + chatlog;
    $("#list").html(chatlog);
}

//讀取name值做爲推送的惟一標示
function onPageLoad(){
    // 獲取URL中的name屬性爲惟一標識符
    var userId = name;
    $("#myName").html(userId);
    // 經過代理，傳入區別本頁面的惟一標識符
    PushMessage.onPageLoad(userId);
 }

　　第六步：效果以下