DWR推送–HelloWorld详解编程语言

• maven 依赖

 <!--dwr--> 
        <dependency> 
            <groupId>org.directwebremoting</groupId> 
            <artifactId>dwr</artifactId> 
            <version>3.0.1-RELEASE</version> 
        </dependency>

• dwr servlet

 <!-- Dwr 推技术 --> 
    <!--  Start  --> 
    <servlet> 
        <servlet-name>dwr-invoke</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> 
        <init-param> 
            <param-name>initApplicationScopeCreatorsAtStartup</param-name> 
            <param-value>true</param-value> 
        </init-param> 
        <load-on-startup>1</load-on-startup> 
    </servlet> 
    <servlet-mapping> 
        <servlet-name>dwr-invoke</servlet-name> 
        <url-pattern>/dwr/*</url-pattern> 
    </servlet-mapping> 
    <!--  End  -->

• 配置dwr.xml (放在和web.xml 同一个目录)

<!DOCTYPE dwr PUBLIC 
        "-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN" 
        "http://www.getahead.ltd.uk/dwr/dwr10.dtd"> 
<dwr> 
<!--定义了DWR能够创建和转换的类，以供 javascript 访问。--> 
    <allow> 
     <!--  <create> 标签中指定 javascript 中可以访问的 java 类，并定义 dwr 应当如何获得要进行远程的类的实例。 
              其中 javascript=" testClass " 属性指定 javascript 代码访问对象时使用的名称。 
              creator是类构造器，creator="new" 属性指定 java 类实例的生成方式， new 意味着 DWR 应当调用类的默认构造函数来获得实例，其他的还有 spring 方式，通过与 IOC 容器 Spring 进行集成来获得实例等等。 --> 
        <create creator="new" javascript="CheckUserStatus"> 
            <param name="class" value="com.lb.mil.service.CheckUserStatusService"/> 
        </create> 
    </allow> 
</dwr>

• 编写CheckUserStatusService

package com.lb.mil.service; 
 
import com.alibaba.fastjson.JSON; 
import com.lb.common.data.json.StatusResult; 
import com.lb.common.utils.ObjectUtils; 
import com.lb.mil.cache.EHCacheConfig; 
import com.lb.mil.cache.EHCacheUtil; 
import com.lb.mil.cache.data.UserState; 
import com.lb.mil.entity.MilInformation; 
import com.lb.mil.entity.MilInformationAttach; 
import org.directwebremoting.ScriptBuffer; 
import org.directwebremoting.ScriptSession; 
import org.directwebremoting.WebContext; 
import org.directwebremoting.WebContextFactory; 
import org.directwebremoting.proxy.dwr.Util; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
 
import java.util.ArrayList; 
import java.util.Collection; 
import java.util.List; 
 
/** 
 * Created by Administrator on 2016/7/18. 
 */ 
public class CheckUserStatusService 
 { 
     protected Logger logger = LoggerFactory.getLogger(CheckUserStatusService.class); 
 
     public void check() 
        { 
            //获取上线下线人员 
            //添加逻辑 
 
            ScriptBuffer scriptBuffer = new ScriptBuffer(); //构造js脚本 
            WebContext webContext= WebContextFactory.get(); 
            String currentPage = webContext.getCurrentPage(); 
            ScriptSession myScSession = webContext.getScriptSession(); 
            if(ObjectUtils.isNotNull(offLineIds)||ObjectUtils.isNotNull(onlineIds)) 
            { 
                 //调用页面的show方法 
                scriptBuffer.appendScript("show(") 
                        .appendData(JSON.toJSONString(statusResult)) 
                        .appendScript(");"); 
                //获取所有浏览当前页面的脚本session 
                Collection<ScriptSession> sessions = webContext.getScriptSessionsByPage(currentPage); 
                //获取请求页面的脚本session   
                //ScriptSession sessions = webContext.getScriptSession(); 
                Util util = new Util(sessions); 
                util.addScript(scriptBuffer); 
            } 
        } 
} 

• 页面调用

  1. 引用js文件(直接引用就行，路径dwr/是web.xml里面里的值，最后一个js，CheckUserStatus.js是dwr.xml里面create javascript属性值)

     <script type='text/javascript' src='${pageContext.request.contextPath }/dwr/engine.js'></script> 
     <script type='text/javascript' src='${pageContext.request.contextPath }/dwr/util.js'></script> 
     <script type='text/javascript' src='${pageContext.request.contextPath }/dwr/interface/CheckUserStatus.js'></script>

  2. 页面body 里添加：

     <body  onload="dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true,true);dwr.engine.setErrorHandler(function(){});">

  3. 添加在java代码中引用的js方法

       function show(msg){ 
       //添加逻辑 
       }

  4. 调用java代码

     // 定时查看用户状态 
     setInterval(getUserStatus,5000);//1000为1秒钟 
     /** 
      * 获取用户状态 
      */ 
     function getUserStatus() 
     { 
         //check为CheckUserStatusService类中的方法，直接调用 
         CheckUserStatus.check(); 
     }