dwr 后台服务器推送技术

忘是亡心i 2022-09-17 05:30 270阅读 0赞

刚才写了一篇《dwr传对象到前台》,现在继续下一个总结点，dwr又一个令人兴奋的技术后台服务器推送技术，需要的包我就不写了

web.xml配置

<servlet>  
  <display-name>DWR Servlet</display-name>  
  <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>activeReverseAjaxEnabled</param-name>  
    <param-value>true</param-value>  
  </init-param>  
  <init-param>  
    
  <param-name>org.directwebremoting.extend.ServerLoadMonitor</param-name>  
  <param-value>org.directwebremoting.impl.PollingServerLoadMonitor</param-value>  
</init-param>  
<init-param>  
  
  <param-name>disconnectedTime</param-name>  
  <param-value>1000</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>

dwr.xml

java代码

user类

package com.dwr.model;  
public class User \{   
 int id ;  
 String  name ;  
 int   number ;    
public User()\{\}  
public User(int id, String name, int number) \{  
super();  
this.id = id;  
this.name = name;  
this.number = number;  
\}  
public int getId() \{  
return id;  
\}  
public void setId(int id) \{  
this.id = id;  
\}  
public String getName() \{  
return name;  
\}  
public void setName(String name) \{  
this.name = name;  
\}  
public int getNumber() \{  
return number;  
\}  
public void setNumber(int number) \{  
this.number = number;  
\}  
@Override  
public String toString() \{  
// TODO Auto-generated method stub  
return "id="+id+"  name="+name+" number="+number;  
\}      
\}

DataPollService 类

package com.dwr.service;  
import java.util.ArrayList;  
import java.util.List;  
import javax.servlet.ServletContext;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpSession;  
import org.directwebremoting.Browser;  
import org.directwebremoting.ScriptBuffer;  
import org.directwebremoting.ScriptSession;  
import org.directwebremoting.ScriptSessionFilter;  
import org.directwebremoting.WebContextFactory;  
import com.dwr.model.User;  
public class DataPollService \{  
ServletContext context  = null ;  
ScriptSession  scriptSession = null ;  
//----给所有的页面推数据，通过Brower.withAllSessions，适合全部页面--------------------------  
  public DataPollService()\{  
           HttpServletRequest request =   WebContextFactory.get().getHttpServletRequest();  
           HttpSession session  =  request.getSession();  
          //初始化工作，目的是用一个服务器级的容器来装scriptsession，便于跨浏览器操作  
           context = session.getServletContext();  
\}  
@SuppressWarnings("unchecked")  
public void initScriptSession()\{  
    System.out.println("into initScriptSession!");  
    //创建一个session，只要页面调用这个方法  
    ScriptSession scriptSession = WebContextFactory.get().getScriptSession();  
   // scriptSession.setAttribute("allpages", scriptSession);  
    //拿到放在scriptSessions中的scriptsession  
List<ScriptSession>   scriptSessions = (List<ScriptSession>) context.getAttribute("scriptSessions" );  
      if(scriptSessions == null)\{  
     scriptSessions = new ArrayList<ScriptSession>() ;  
      \}  
    //添加一个新的scriptsession  
    scriptSessions.add(scriptSession);  
    context.setAttribute("scriptSessions", scriptSessions);  
 \}  
   
  
@SuppressWarnings("unchecked")  
public void pollDataToAllPage()\{  
System.out.println("into pollDataToCpage!");  
//拿出所有的session   
final List<ScriptSession>   scriptSessions =  (List<ScriptSession>) context.getAttribute("scriptSessions" );  
if (scriptSessions ==null) \{  
return ;  
\}  
    System.out.println("scriptSessions.size()="+scriptSessions.size());  
Browser.withAllSessions(new Runnable() \{  
   
@Override  
public void run() \{  
//掉用浏览器客户端的js函数，实现推送数据  
  System.out.println("run");  
    ScriptBuffer scriptBuffer = new ScriptBuffer();   
// 只要有页面有这个js函数，即可以推送  
scriptBuffer.appendScript("polledDataByServer(") .appendData( new User(1,"张三",1)).appendScript(");");  
for(ScriptSession scriptSession :scriptSessions)\{  
//推送数据  
scriptSession.addScript(scriptBuffer);   
\}  
\}  
\});  
   
\}  
//-------------------------------给D页面推数据，通过Brower.withSession,通过sessionId来定位，适合指定页面-------------  
  
  //创建一个sessionId属于D页面的  
public void createSessionId()\{  
        ScriptSession  scriptSession = WebContextFactory.get().getScriptSession();  
//  scriptSession.setAttribute("", arg1);  
    //  sessionIdString = scriptSession.getId();  
        //通过sessionid来定位  
     context.setAttribute("sessionId", scriptSession.getId());  
     context.setAttribute("scriptSession", scriptSession);  
      System.out.println("into createSessionId! sessonId= "+scriptSession.getId());  
        
           
        \}  
   
public void pollDataToSpePage()\{  
   
  //执行和操作的scriptSessionId 必须是由createSessionId创建的session所产生，因此需要在创建session的时候，将scriptsesson保留在context里面  
final ScriptSession  scriptSession = (ScriptSession) context.getAttribute("scriptSession");  
        String sesssionId = (String) context.getAttribute("sessionId");  
        System.out.println("into pollDataToSpePage sessionId="+sesssionId +"  scriptSession="+scriptSession);  
       
     Browser.withSession(sesssionId, new Runnable() \{  
  
@Override  
public void run() \{  
// TODO Auto-generated method stub  
 System.out.println("run");  
    ScriptBuffer scriptBuffer = new ScriptBuffer();   
// 只要有页面有这个js函数，即可以推送  
scriptBuffer.appendScript("polledDataToOneByServer(") .appendData( new User(1,"张三",1)).appendScript(");");  
  
//推送数据,  
scriptSession.addScript(scriptBuffer);   
  
\}  
\});  
   
\}  
\}

jsp代码

A.jsp代码，用来触发动作传到服务器，服务器根据需要推送数据给需要的页面，可以群发，也可以指定页面发，具体上上面的java代码

<script src='<%=request.getContextPath() %>/dwr/engine.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/util.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/interface/DataPollService.js'></script>  
<script type="text/javascript">  
function clickMe()\{  
   //alert()  
    dwr.engine.setActiveReverseAjax(true);  
DataPollService.pollDataToAllPage();  
  
\}  
function clickMe1()\{  
// alert()  
   dwr.engine.setActiveReverseAjax(true);  
DataPollService.pollDataToSpePage();  
\}  
</script>  
<title>A页面</title>  
</head>  
<body>  
  
  
<input type="button" value="请求服务器推送数据给所有的页面" οnclick="clickMe()">  
<input type="button" value="请求服务器推送数据给D页面" οnclick="clickMe1()">  
</body>  
</html>

B.jsp 页面代码

<%@ page language="java" contentType="text/html; charset=GB18030"  
    pageEncoding="GB18030"%>  
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
<html>  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">  
  
<script src='<%=request.getContextPath() %>/dwr/engine.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/util.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/interface/DataPollService.js'></script>  
<script type="text/javascript">  
window.οnlοad=function()\{  
//将后台推送数据给前台设置为true  
  dwr.engine.setActiveReverseAjax(true);  
//创建一个属于这个页面的scriptSession  
 DataPollService.initScriptSession();  
\};  
//等待服务器的数据推送,data是服务器推过来的数据，不仅仅是字符串，还可以是其他的任何对象，如果是对象，记得要在dwr中进行转化  
function polledDataByServer(data)\{  
  
 dwr.util.setValue("data","我是服务器推过来的数据: "+data.name);  
\}  
</script>  
<title>B页面</title>  
</head>  
<body>  
我是B客户端，我不刷新页面，等待服务给我推数据<br><br>  
<font color="red" id="data"></font>  
</body>  
</html>

D页面代码

<%@ page language="java" contentType="text/html; charset=GB18030"  
    pageEncoding="GB18030"%>  
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
<html>  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">  
  
<script src='<%=request.getContextPath() %>/dwr/engine.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/util.js'></script>  
<script src='<%=request.getContextPath() %>/dwr/interface/DataPollService.js'></script>  
<script type="text/javascript">  
window.οnlοad=function()\{  
//将后台推送数据给前台设置为true  
  dwr.engine.setActiveReverseAjax(true);  
//创建一个属于这个页面的scriptSessionId  
 DataPollService.createSessionId();  
\};  
//等待服务器的数据推送,data是服务器推过来的数据，不仅仅是字符串，还可以是其他的任何对象，如果是对象，记得要在dwr中进行转化  
function polledDataToOneByServer(data)\{  
  
 dwr.util.setValue("data","我是服务器推过来的数据: "+data.name);  
\}  
</script>  
<title>D页面</title>  
</head>  
<body>  
我是D客户端，我不刷新页面，等待服务给我推数据<br><br>  
<font color="red" id="data"></font>  
</body>  
</html>

看到这里之后，发现java后台服务器根据前台浏览器初始化的session和调用前台的页面js函数来实现群发还有指定页面发送...这就是dwr的

后台服务器的推送技术