DWR实现服务器推简单demo

向右看齐 2022-08-18 03:16 201阅读 0赞

# 本文目的： #

利用开源DWR，实现客户端页面不用刷新就可以显示服务器发送过来的数据。这是一个jsp+tomcat+dwr的简单例子。具体的理论性知识参考dwr官网。

文章最后附带MyEclipse的源工程下载。

# 准备工作： #

1、DWR官网下载3.0的jar包

地址： https://java.net/downloads/dwr/DWR\_3.x/3.0\_RC2/dwr.jar

2、在web工程中加入所依赖的文件

具体添加依赖文件的过程可以参考：[DWR中文文档][DWR]的第一章“DWR入门”，或者参考DWR官网[Getting Started with DWR][] 中的配置。

依赖的文件有：刚才下载的dwr.jar包、Commons Logging jar

# 编辑配置文件 #

## 1、配置web.xml ##

将如下的代码添加到WEB-INF/web.xml，在web.xml中所有的<servlet>要放在一起，所有的<servlet-mapping>区域也是一样。关于web.xml的具体配置可以参考上述提供的文档。

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
      <display-name>dwr_test</display-name>
      <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
      </welcome-file-list>
      
      <listener>
        <listener-class>org.directwebremoting.servlet.DwrListener</listener-class>
      </listener>
      
      <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>
        
      <load-on-startup>1</load-on-startup>
    </servlet>
    
    
        <servlet>
            <servlet-name>MySevlet</servlet-name>
            <servlet-class>dwr_test.MySevlet</servlet-class>
        </servlet>
    
        
        <servlet-mapping>
            <servlet-name>MySevlet</servlet-name>
            <url-pattern>/server/push</url-pattern>
        </servlet-mapping>
    
    <servlet-mapping>
      <servlet-name>dwr-invoker</servlet-name>
      <url-pattern>/dwr/*</url-pattern>
    </servlet-mapping>
    
    </web-app>

## 2、配置dwr.xml ##

创建新的xml文件，命名为dwr。具体字段含义请参考上述给出的参考文档。

<?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="service">
    			<param name="class" value="dwr_test.Service" />
    		</create>
    	</allow>
    </dwr>

## 3、推送程序 ##

//Service.java
    package dwr_test;
    
    /*public class Service {
    	public String sayHello(String yourName) {
    		return "Hello World " + yourName;
    	}
    }*/
    
    
    import org.directwebremoting.Browser;
    import org.directwebremoting.ScriptSessions;
    import org.directwebremoting.ServerContextFactory;
    import org.directwebremoting.WebContext;
    import org.directwebremoting.WebContextFactory;
    import org.directwebremoting.ui.dwr.Util;
    import java.text.*;
    import java.util.*;
    
    public class Service{
        
        public static void sendMsg(final String msg){    
            //WebContext wctx = WebContextFactory.get();
            //Browser.withPage("/MyDWRSample/",new Runnable(){
        	//针对具体的页面first_test.jsp页面进行推送
            String page = ServerContextFactory.get().getContextPath() + "/first_test.jsp";
            //System.out.println(page);
            Browser.withPage(page ,new Runnable(){
            public void run(){
                //ScriptSessions.addFunctionCall("show", msg);
            	//messageid字段是向jsp页面推送时所对应的字段，msg是要推送的消息
            	Util.setValue("messageid", msg);
            }
        });
         
        }
    
    }

这个程序包含的函数sendMsg负责向客户端推送消息。

## 4、模拟servlet，模拟请求服务 ##

//MyServlet.java，注意工程中这个文件的名字书写错误，好囧
    package dwr_test;
    
    import java.io.IOException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /*import org.directwebremoting.ServerContext;
    import org.directwebremoting.ServerContextFactory;
    import org.directwebremoting.WebContextFactory.WebContextBuilder;
    import org.directwebremoting.impl.DefaultWebContextBuilder;*/
    
    public class MySevlet extends HttpServlet {
        private static final long serialVersionUID = 1L;
    
        protected void doGet(HttpServletRequest request,
                HttpServletResponse response) throws ServletException, IOException {
     /*           ServerContext sc = ServerContextFactory.get () ;
                WebContextBuilder webBuilder = new DefaultWebContextBuilder () ;
                webBuilder.engageThread (sc.getContainer (), request, response) ;*/
                doPost(request, response);
        }
    
        protected void doPost(HttpServletRequest request,
                HttpServletResponse response) throws ServletException, IOException {
                
              //  PrintWriter out = response.getWriter();
        	SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        	Service.sendMsg( "time: " + df.format(new Date()) + "  aaaaaa"); 
             //  out.write("aaaaa");
        }
    }

这个servlet用来模拟请求，当请求到来的时候，servlet调用sendMsg方法来向客户端推送当前时间以及字符串“aaaaaa”。

## 5、客户端页面first\_test.jsp ##

这个页面用来接收服务器的推送。

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!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=UTF-8">
    <title>Insert title here</title>
    
    	 <script type='text/javascript' src='/dwr_test/dwr/engine.js'></script>
    	 <script type='text/javascript' src='/dwr_test/dwr/util.js'></script>
    	 <script type='text/javascript' src='/dwr_test/dwr/interface/service.js'></script>
    
    	<script>
    	function my_onload(){	
    			dwr.engine.setActiveReverseAjax(true);
    	}
    	
    	function show(message){
    		alert(message);
    		document.getElementById('messageid').value=message;
    	}
    	
    	</script>
    
    </head>
    <body οnlοad="my_onload();">
     从服务端得到的消息:<br /> <input type="text" style="width:230px" id="messageid" value="" />
    
    </body>
    </html>

# 程序演示： #

输入链接http://localhost:8080/dwr\_test/first\_test.jsp，打开客户端页面：

![SouthEast][]

浏览器输入链接http://localhost:8080/dwr\_test/server/push，模拟请求，这时客户端会显示当前时间以及字符串“aaaaaa"：

![SouthEast 1][]

![SouthEast 2][]

# MyEclipse工程下载： #

[http://download.csdn.net/detail/u013074465/9338055][http_download.csdn.net_detail_u013074465_9338055]

本人刚刚接触web的东西，java也是刚开始学习，代码很劣质，希望指教。

# 参考 #

[http://xiaoliang330.iteye.com/blog/1359874][http_xiaoliang330.iteye.com_blog_1359874]

[http://www.yihaomen.com/article/java/551.htm][http_www.yihaomen.com_article_java_551.htm]

[DWR]: http://download.csdn.net/detail/u013074465/9337959
[Getting Started with DWR]: http://directwebremoting.org/dwr/introduction/getting-started.html
[SouthEast]: /images/20220731/b28fe9601b204b089be8366881dd9241.png
[SouthEast 1]: /images/20220731/cebc866335074592b78551fbe7ab8dbe.png
[SouthEast 2]: /images/20220731/e9940d34af974e4abc9df14ff857dd76.png
[http_download.csdn.net_detail_u013074465_9338055]: http://download.csdn.net/detail/u013074465/9338055
[http_xiaoliang330.iteye.com_blog_1359874]: http://xiaoliang330.iteye.com/blog/1359874
[http_www.yihaomen.com_article_java_551.htm]: http://www.yihaomen.com/article/java/551.htm