場景：頁面comet.jsp接受服務器推送的信息并顯示，頁面action.jsp執行一個動作，調用DwrServer.perform方法，perform方法做某些事，并發送事件信息PerformInfo。NotifyClient監聽事件，當接收到PerformInfo后，把PerformInfo的信息發送到comet.jsp頁面。這個場景模擬了頁面1執行了一個時間比較長或復雜的任務，任務執行情況可以反饋到頁面2(比如模式窗口)。
信息載體PerformInfo.java
package application.comet;
import java.util.Date;
public class PerformInfo {
private int id;
private String msg;
private Date time;
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the msg
*/
public String getMsg() {
return msg;
}
/**
* @param msg the msg to set
*/
public void setMsg(String msg) {
this.msg = msg;
}
/**
* @return the time
*/
public Date getTime() {
return time;
}
/**
* @param time the time to set
*/
public void setTime(Date time) {
this.time = time;
}
}
package application.comet;
import java.util.Date;
public class PerformInfo {
private int id;
private String msg;
private Date time;
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the msg
*/
public String getMsg() {
return msg;
}
/**
* @param msg the msg to set
*/
public void setMsg(String msg) {
this.msg = msg;
}
/**
* @return the time
*/
public Date getTime() {
return time;
}
/**
* @param time the time to set
*/
public void setTime(Date time) {
this.time = time;
}
}
Spring的事件InfoEvent.java
package application.comet;
import org.springframework.context.ApplicationEvent;
public class InfoEvent extends ApplicationEvent {
public InfoEvent(Object source){
super(source);
}
}
DwrService.java 執行任務，就是寫了100遍PerformInfo,需要實現ApplicationContextAware接口
package application.comet;
import java.util.Date;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEvent;
public class DwrService implements ApplicationContextAware{
private ApplicationContext ctx;
public void setApplicationContext(ApplicationContext ctx) {
this.ctx = ctx;
}
public void perform(){
for (int i=0;i<100;i++){
PerformInfo info = new PerformInfo();
info.setId(i);
info.setMsg("發送"+i+"信息");
info.setTime(new Date());
InfoEvent evt = new InfoEvent(info);
ctx.publishEvent(evt);
}
}
}
NotifyClient.java監聽事件，發送信息到頁面。實現ApplicationListener,ServletContextAware接口，對中文需要編碼
package application.comet;
import java.io.UnsupportedEncodingException;
import java.util.Collection;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import org.springframework.web.context.ServletContextAware;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
public class NotifyClient implements ApplicationListener,ServletContextAware{
private ServletContext servletContext = null;
public void setServletContext( ServletContext servletContext )
{
this.servletContext = servletContext;
}
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof InfoEvent) {
PerformInfo info = (PerformInfo)event.getSource();
System.out.println(info.getMsg());
//Collection<ScriptSession> sessions=ctx.getAllScriptSessions();
ServerContext ctx = ServerContextFactory.get(servletContext );
Collection<ScriptSession> sessions =
ctx.getScriptSessionsByPage("/dwrcomet/comet.jsp");
for (ScriptSession session : sessions) {
ScriptBuffer script = new ScriptBuffer();
String s=null;
String s2 = null;
try {
s = java.net.URLEncoder.encode(info.getMsg(),"UTF-8");
s2 = java.net.URLEncoder.encode("通知結束","UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
if (info.getId()<99){
script.appendScript("putInfo('")
.appendScript(info.getId()+":"+s)
.appendScript("');");
}else{
script.appendScript("alert(decodeURI('").
appendScript(s2).appendScript("'));");
}
System.out.println(script.toString());
session.addScript(script);
}
}
}
}
action.jsp執行任務
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String root = request.getContextPath();
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>doing</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='<%=root%>/dwr/engine.js'></script>
<script type='text/javascript' src='<%=root%>/dwr/util.js'></script>
<script type='text/javascript' src='<%=root%>/dwr/interface/DwrService.js'></script>
</head>
<body>
<input name='action' onclick='DwrService.perform();' type="button" value="行動"/>
</body>
</html>
comet.jsp接受信息。關鍵是增加onload="dwr.engine.setActiveReverseAjax(true);",還可以根據user或session id判斷是否是自己的信息.
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String root = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"
+request.getServerPort()+root+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>Comet with DWR</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
</head>
<body onload="dwr.engine.setActiveReverseAjax(true);">
<script type='text/javascript' src='<%=root%>/dwr/engine.js'></script>
<script type='text/javascript' src='<%=root%>/dwr/util.js'></script>
<script type="text/javascript">
var user = '<%=request.getParameter("user")%>';
function putInfo(data) {
var d = decodeURI(data);
var text = dwr.util.getValue('info');
dwr.util.setValue('info',text+'\n'+d);
}
</script>
<br/>
<textarea rows="20" cols="100" id='info'></textarea>
</body>
</html>
applicationContext.xml配置了NotifyClient和DwrService，這兩個bean實現了ApplicationContextAware
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<bean id="notifyClient" class="application.comet.NotifyClient">
</bean>
<bean id="dwrService" class="application.comet.DwrService"></bean>
</beans>
dwr.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN"
"http://www.getahead.ltd.uk/dwr/dwr10.dtd">
<dwr>
<allow>
<create creator="spring" javascript="DwrService">
<param name="beanName" value="dwrService" />
</create>
</allow>
</dwr>
web.xml定義了dwr的comet控制，關鍵是pollAndCometEnabled=true
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/app*.xml</param-value>
</context-param>
<servlet>
<servlet-name>context</servlet-name>
<servlet-class>
org.springframework.web.context.ContextLoaderServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<!--dwr servlet-->
<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>pollAndCometEnabled</param-name>
<param-value>true</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>
</web-app>
運行時要先打開comet.jsp,然后執行action.jsp