前面一章讲解了DWR页面js代码如何直接调用后台服务器端java方法，今天这一章讲解如何在服务器端之间push数据到页面。
一。工程还沿用上一节的DwrDemo工程（不懂的可以先查看下上一章的内容）
首先需要修改web.xml文件
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns=""xmlns:xsi=""xsi:schemaLocation=" "><display-name></display-name><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list><!– 配置DWR –><servlet><servlet-name>dwr-invoker</servlet-name><servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class><init-param><param-name>debug</param-name><param-value>true</param-value></init-param><span style="color:#ff0000;"><!– 开启DWR反向ajax功能 –><init-param><param-name>activeReverseAjaxEnabled</param-name><param-value>true</param-value></init-param></span></servlet><servlet-mapping><servlet-name>dwr-invoker</servlet-name><url-pattern>/dwr/*</url-pattern></servlet-mapping></web-app>然后：
<%@ 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"><script type='text/javascript' src='/DwrDemo/dwr/engine.js'></script><script type='text/javascript' src='/DwrDemo/dwr/util.js'></script><script type='text/javascript' src='/DwrDemo/dwr/interface/DwrDemo.js'></script><script type="text/javascript">function dwrdemo() {//调用服务器段的DwrDemo类的getServerData方法,serverReturn是回调方法DwrDemo.getServerData(serverReturn);}function serverReturn(data) {dwr.util.setValue("val", data);}function dwrdemo1() {DwrDemo.getPerson(serverReturn1);}function serverReturn1(data) {dwr.util.setValue("val1", data.name + ":" + data.age + ":"+ data.address);}<span style="color:#ff0000;">//服务器端会调用这个js来向前端的输入框里面设置数据function serverPush(data) {var v = dwr.util.getValue("box") ;dwr.util.setValue("box",v+data) ;}</span></script></head><span style="color:#ff0000;"><!– 需要在页面onload的时候设置反向ajax是true –><body onload="dwr.engine.setActiveReverseAjax(true);"></span><button name="btn" onclick="dwrdemo()" title="click me">clickme</button>返回值:<input type="text" id="val" name="val"><button name="btn1" onclick="dwrdemo1()">获得用户</button>用户信息:<input type="text" id="val1" name="val1"><div><input type="text" id="box" name="box"></div></body></html>最后修改java代码：
package cn.gov.zjport.dwr;import java.util.Collection;import org.directwebremoting.ScriptBuffer;import org.directwebremoting.ScriptSession;import org.directwebremoting.proxy.dwr.Util;import uk.ltd.getahead.dwr.WebContext;import uk.ltd.getahead.dwr.WebContextFactory;public class DwrDemo {public String getServerData() {serverPush();return "Message from server";}public Person getPerson() {Person person = new Person();person.setName("张三");person.setAge(32);person.setAddress("杭州下城区");return person;}<span style="color:#ff0000;">/** * 开启一个线程用来定时的向前端来push数据 */public void serverPush() {d dd = new d(getSessions());dd.start();}public Collection<ScriptSession> getSessions(){WebContext content = WebContextFactory.get();Collection<ScriptSession> session = content.getAllScriptSessions();return session ;}</span>}class d extends Thread {private Collection<ScriptSession> sessions;public d(Collection<ScriptSession> sessions) {this.sessions = sessions;}@Overridepublic void run() {int i = 1;while (true) {for (ScriptSession session : sessions) {push(i, session);}i++;try {Thread.sleep(2000);} catch (Exception ex) {ex.printStackTrace();}}}<span style="color:#ff0000;">/** * 调用前端js方法:serverPush(data) * @param i * @param session */public void push(int i, ScriptSession session) {ScriptBuffer buffer = new ScriptBuffer();buffer.appendScript("serverPush(");buffer.appendData(i);buffer.appendScript(")");Util util = new Util(session);util.addScript(buffer);System.out.println("—-");}</span>}运行结果：
首先开启几个窗口然后点击其中一个串口的click me按钮会发现其他窗口的最后一个输入框也会出现数据:
第一幅图：
而有的旅行是释放负面情绪，换个心情，轻装上阵。
