一、DWR介绍

DWR（Direct Web Remoting）可用于实现javascript直接调用java函数和后台直接调用页面javascript代码，后者可用作服务端推送消息到Web前端。

二、环境搭建

1.dwr-3.0.0-RELEASE.jar（在maven中央仓库下载）

2.spring-3.2.2.RELEASE

3.jdk1.7

三、dwr配置

1.在resources下创建dwr.xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://getahead.org/dwr/dwr20.dtd">
<dwr>
    <allow>
        <!-- 建立JS对象，将目标对象的方法转换成JS对象的方法 -->
        <create javascript="dwrPush" creator="new">
            <param name="class" value="com.yudu.dwr.DwrPush"></param>
        </create>
        <!-- 指定针对于特定对象的转换器 -->
        <convert match="entity.*" converter="bean"></convert>
        <convert match="java.lang.Throwable" converter="bean">
            <param name="include" value="message"></param>
        </convert>
    </allow>
</dwr>

2.web.xml配置

<!-- 配置DWR前端控制器 -->
  <servlet>
      <servlet-name>dwrServlet</servlet-name>
      <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class>
      <!-- 指定配置文件 -->
      <init-param>
          <param-name>config</param-name>
          <!-- 如果有多个用","分开 -->
          <param-value>
              /WEB-INF/classes/dwr.xml                
          </param-value>
      </init-param>
      <init-param>
          <param-name>debug</param-name>
          <param-value>true</param-value>
      </init-param>
      <!-- 设置使用反向Ajax技术 -->
       <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>
       <!--长连接只保持时间 -->
        <param-name>maxWaitAfterWrite</param-name>
        <param-value>60</param-value>
       </init-param>
  </servlet>

四、后端

package com.yudu.dwr;

import java.util.Collection;

import javax.servlet.http.HttpSession;

import org.directwebremoting.Browser;
import org.directwebremoting.Container;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessionFilter;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;
import org.directwebremoting.extend.ScriptSessionManager;
import org.directwebremoting.servlet.DwrServlet;
import com.ccc.system.model.UserInfo;


public class DwrPush{

    public void onPageLoad(String userId){
        ScriptSession scriptSession = WebContextFactory.get().getScriptSession();
        scriptSession.setAttribute(userId, userId);
        DwrScriptSessionManagerUtil  dssmu = new DwrScriptSessionManagerUtil();
        dssmu.init();
    }
    
    public void sendMsg(String userid,String org){
        final String userId = userid;
        final String msg = org;
        final String jsFunc = "receiveMsg";
        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(){
                script = script.appendScript(jsFunc+"(");
                script = script.appendData(msg);
                script = script.appendScript(")");
                Collection<ScriptSession> sessions = Browser.getTargetSessions();
                for(ScriptSession scriptSession : sessions){
                    scriptSession.addScript(script);
                }
            }
        });
    }
    class DwrScriptSessionManagerUtil extends DwrServlet{
        private static final long serialVersionUID = -7504612622407420071L;
        
        public void init(){
            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 =((UserInfo) session.getAttribute("userinfo")).getUserInfoId()+"";
                     ev.getSession().setAttribute("userId", userId);
              }
              public void sessionDestroyed(ScriptSessionEvent ev) {}
            };
            manager.addScriptSessionListener(listener);
        }
    }
}

五、前端
1.查看http://ip:port/program/dwr/

image.png

<script type='text/javascript' src='/traveloa/dwr/engine.js'></script>
<script type='text/javascript' src='/traveloa/dwr/interface/dwrPush.js'></script>
<script type='text/javascript' src='/traveloa/dwr/util.js'></script>
<script>
function init(){
    dwr.engine.setActiveReverseAjax(true);
    dwr.engine.setNotifyServerOnPageUnload(true);
    var userId='${userInfo.userInfoId}';
    dwrPush.onPageLoad(userId);
}
window.onload = init;
function send(msg){
    var userId='${userInfo.userInfoId}';
    dwrPush.sendMsg(userId,msg);
}
function receiveMsg(msg){
    alert(dwr.util.toDescriptiveString(msg));
}
</script>