Java Dwr3實現消息推送步驟詳解

時間 2019-11-07

標籤 java dwr3 dwr 實現消息推送步驟詳解欄目 Java 简体版

原文原文鏈接

一、在工程中引入dwr.jar，以後修改配置web.xml文件，添加配置具體代碼以下：
javascript

<servlet>
        <servlet-name>dwr-invoker</servlet-name>
        <servlet-class>
            org.directwebremoting.servlet.DwrServlet
        </servlet-class>
        <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>3000</param-value>
        </init-param>
        <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>
    </servlet>

二、在web.xml統計目錄下新增dwr.xml文件，具體內容以下：html

<!DOCTYPE dwr PUBLIC
          "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN"
          "http://getahead.org/dwr/dwr30.dtd">
     <dwr>
          <alow>
               <create creator="new" javascript="MessagePush">
                 <param name="class" value="com.yoodb.service.MessagePush"/>
              </create>
	      <create creator="new" javascript="TestPush">  
                  <param name="class" value="com.yoodb.service.TestPush"/>  
              </create>
          </alow>
     </dwr>

MessagePush在頁面的javascript中使用，com.yoodb.service.MessagePush實現了想要調用的方法，其中MessagePush.java對被推送頁面開放的java類，Test.java是對推送頁面開放的java類。在javascript中使用MessagePush.java類中實現的方法，便可在dwr中調用。
java

三、引入JavaScript文件，具體以下：web

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

注意：session

1)dwr.xml配置的javascript中engine.js和util.js是必須引入的文件。app

2)在任何一個用戶登陸的時候，都須要將其userId或者其餘惟一性標識放入session中，我放的是userId，這裏就以userId爲惟一性標識。jsp

3)在載入想推送的頁面時，須要onload一個我在MessagePush類中實現的方法，固然了，須要使用dwr調用ui

被推送html頁面具體內容代碼以下：spa

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>  
<%  
String path = request.getContextPath();  
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
%>  
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
<html>  
  <head>  
    <base href="<%=basePath%>">  
    <title>DWR  DEMO</title>  
    <meta http-equiv="pragma" content="no-cache">  
    <meta http-equiv="cache-control" content="no-cache">  
    <meta http-equiv="expires" content="0">      
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
    <meta http-equiv="description" content="This is my page">  
  </head>  
  <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/MessagePush.js"></script>  
  
  <script type="text/javascript">  
        //經過該方法與後臺交互，確保推送時能找到指定用戶  
         function onPageLoad(){  
            var userId = '${userinfo.userId}';  
            MessagePush.onPageLoad(userId);  
          }  
         //推送信息  
         function showMessage(autoMessage){  
                alert(autoMessage);      
        }  
  </script>  
  <body onload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);;">   
    This is my DWR DEOM page. <hr>  
    <br>  
    <div id="DemoDiv">demo</div>  
  </body>  
</html>

其中MessagePush.java文件中實現方法，以下：debug

public class MessagePush{  
	public void onPageLoad(String userId) {  
    	   ScriptSession scriptSession = WebContextFactory.get().getScriptSession();  
   	    scriptSession.setAttribute(userId, userId);  
  	     DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil();  
 	      try {  
 	             dwrScriptSessionManagerUtil.init();  
 	             System.out.println("cacaca");  
 	      } catch (ServletException e) {  
 	             e.printStackTrace();  
	       }  
	}  
}

對於onPageLoad()方法中DwrScriptSessionManagerUtil類的實現，具體以下：

import javax.servlet.ServletException;  
import javax.servlet.http.HttpSession;  
  
import org.directwebremoting.Container;  
import org.directwebremoting.ServerContextFactory;  
import org.directwebremoting.WebContextFactory;  
import org.directwebremoting.event.ScriptSessionEvent;  
import org.directwebremoting.event.ScriptSessionListener;  
import org.directwebremoting.extend.ScriptSessionManager;  
import org.directwebremoting.servlet.DwrServlet;  
  
public class DwrScriptSessionManagerUtil extends DwrServlet{  
  
    private static final long serialVersionUID = -7504612622407420071L;  
  
    public void init()throws ServletException {  
  
           Container container = ServerContextFactory.get().getContainer();  
           ScriptSessionManager manager = container.getBean(ScriptSessionManager.class);  
           ScriptSessionListener listener = new ScriptSessionListener() {  
                  public void sessionCreated(ScriptSessionEvent ev) {  
                         HttpSession session = WebContextFactory.get().getSession();  
  
                         String userId =((User) session.getAttribute("userinfo")).getHumanid()+"";  
                         System.out.println("a ScriptSession is created!");  
                         ev.getSession().setAttribute("userId", userId);  
                  }  
                  public void sessionDestroyed(ScriptSessionEvent ev) {  
                         System.out.println("a ScriptSession is distroyed");  
                  }  
           };  
           manager.addScriptSessionListener(listener);  
    }  
}

四、推送html頁面具體內容代碼以下：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>  
<%  
String path = request.getContextPath();  
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
%>  
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
<html>  
  <head>  
    <base href="<%=basePath%>">  
    <title>My JSP 'MyJsp.jsp' starting page</title>  
    <meta http-equiv="pragma" content="no-cache">  
    <meta http-equiv="cache-control" content="no-cache">  
    <meta http-equiv="expires" content="0">      
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
    <meta http-equiv="description" content="This is my page">  
    <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/TestPush.js'></script>  
      
    <script type="text/javascript">  
      
    function testPush() {  
        var msg = document.getElementById("msgId").value;  
        TestPush.sendMessageAuto(msg,"www.yoodb.com");  
          
    }  
    </script>  
  </head>  
    
  <body>  
    id值: <input type="text" name="msgId" id="msgId" /> <br />  
    <input type="button" value="Send" onclick="testPush()"  />  
  </body>  
</html>

其中TeshPush.java文件，具體內容以下：

public class TestPush{  
    public void sendMessageAuto(String userid, String message){  
          
        final String userId = userid;  
        final String autoMessage = message;  
        Browser.withAllSessionsFiltered(new ScriptSessionFilter() {  
            public boolean match(ScriptSession session){  
                if (session.getAttribute("userId") == null)  
                    return false;  
                else  
                    return (session.getAttribute("userId")).equals(userId);  
            }  
        }, new Runnable(){  
              
            private ScriptBuffer script = new ScriptBuffer();  
              
            public void run(){  
                  
                script.appendCall("showMessage", autoMessage);  
                  
                Collection<ScriptSession> sessions = Browser  
  
                .getTargetSessions();  
                  
                for (ScriptSession scriptSession : sessions){  
                    scriptSession.addScript(script);  
                }  
            }  
        });  
    }  
}