DWR（Direct Web Remoting）是一个用于改善web页面与Java类交互的远程服务器端Ajax开源框架，可以帮助开发人员开发包含AJAX技术的网站。它可以允许在浏览器里的代码使用运行在WEB服务器上的JAVA函数，就像它就在浏览器里一样。
其实这些配置也是网上大神们的，只是拿出来整理下，少走弯路。
首先需要导入dwr3.0.jar，
然后在web.xml中加入
<!-- dwr配置 -->
<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>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>false</param-value>
</init-param>
<init-param>
<param-name>logLevel</param-name>
<param-value>WARN</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping> 在webapps下新建dwr.xml（文件名不能改）
<?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="MessagePush">
<param name="class" value="cn.qnight.common.MessagePush"/>
</create>
</allow>
</dwr>再新建一个MessagePush.java就完成dwr的配置，但是我们需要做收邮件提示得还需要一些改进。
新建 DwrScriptSessionManagerUtil.java
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 = ((Employee) session.getAttribute("loginuser")).getId();
ev.getSession().setAttribute("userId", userId);
}
public void sessionDestroyed(ScriptSessionEvent ev) {
}
};
manager.addScriptSessionListener(listener);
}
}新建MessagePush.java 初始化
public class MessagePush {
public void onPageLoad(String userId) {
ScriptSession scriptSession = WebContextFactory.get().getScriptSession();
scriptSession.setAttribute(userId, userId);
DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil();
try {
dwrScriptSessionManagerUtil.init();
} catch (ServletException e) {
e.printStackTrace();
}
}
}
最后我们在定义一个服务器发送消息的实体就行了
public class SendMessageAuto {
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() {
/* 前台接收的function 名为showMessage， 消息 是autoMessage */
script.appendCall("showMessage", autoMessage);
Collection<ScriptSession> sessions = Browser
.getTargetSessions();
for (ScriptSession scriptSession : sessions) {
scriptSession.addScript(script);
}
}
});
}
}需要在接收页面上的js
<script type="text/javascript" src="${ctx }/dwr/engine.js"></script>
<script type="text/javascript" src="${ctx }/dwr/util.js"></script>
<script type="text/javascript" src="${ctx }/dwr/interface/MessagePush.js"></script>body 需要加入
<body onload="dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);onPageLoad();">
加入js代码
/* dwr初始化 */
function onPageLoad(){
var userId = '${loginuser.id}';
MessagePush.onPageLoad(userId);
}
/* dwr接收消息 */
function showMessage(autoMessage) {
alertMsg.info(autoMessage);
}客户端响应的是showMessage这个函数，这样我们就可以完成这个功能了。