dwr入门 -

java110eye · 发表于 2013-1-29 09:29:58

1、在web.xml添加一段代码,解决上一篇第一访问时的错：DefaultContainer can't find a classes。修改结果如下：
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list><servlet><servlet-name>dwr-invoker</servlet-name><servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class><init-param><description></description><param-name>debug</param-name><param-value>true</param-value></init-param><init-param>          <param-name>classes</param-name>          <param-value>java.lang.Object</param-value>       </init-param> </servlet><servlet-mapping><servlet-name>dwr-invoker</servlet-name><url-pattern>/dwr/*</url-pattern></servlet-mapping></web-app> 2、现在我们传递使用javabean, 首先建个javabean：
package com.xx;import java.io.Serializable;public class UserBean implements Serializable {private String name;private String pwd;public UserBean() {}public UserBean(String name, String pwd) {this.name = name;this.pwd = pwd;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPwd() {return pwd;}public void setPwd(String pwd) {this.pwd = pwd;}} 然后修改Test类里的hello方法：

package com.xx;public class Test {public UserBean hello(UserBean user) {//return "您好！" + user.getName() + ", 您的密码是: " + user.getPwd();return user;}} 3、传递javabean需要在dwr.xml配置文件中做一些修改：
<!DOCTYPE dwr PUBLIC    "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"    "http://www.getahead.ltd.uk/dwr//dwr20.dtd"><dwr><allow><create creator="new" javascript="Hello"><param name="class" value="com.xx.Test" /></create><convert match="com.xx.UserBean" converter="bean" /></allow></dwr> 4、JSP也改下,有用户名和密码：
<%@ 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 : hello word</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"><meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><script type='text/javascript' src='<%=basePath%>dwr/interface/Hello.js'></script><script type='text/javascript' src='<%=basePath%>dwr/engine.js'></script><script type='text/javascript' src='<%=basePath%>dwr/util.js'></script><script type='text/javascript' src='<%=basePath%>hello.js'></script></head><body><input id="user_name" type="text" /><input id="user_pwd" type="password" /><input type='button' value='提交' onclick='hello();' /><div id="result"></div></body></html> 5、最后就是交互的hello.js文件修改：
function hello() {var user_name = $('user_name').value; // document.getElementById("user_name").value// 或者 DWRUtil.getValue("user_name") 直接取值var user_pwd = DWRUtil.getValue("user_pwd");var user = {name:user_name, pwd:user_pwd };Hello.hello(user, callback);}// 回调函数function callback(msg) {//DWRUtil.setValue('result', msg);for(var property in msg){ alert("property:"+property); alert(property+"的值是:"+msg[property]); }// 知道属性名的情况下直接msg.name}/* DWRUtil.getText("id"),返回一个select下拉菜单中的text值.仅适用于select类型的元素.  * DWRUtil.onReturn(event, submitFunction) 定义在输入框中按回车的响应,可以防止执行submit.  */ 6、OK.部署,启动服务器,访问！

1、要注意DWR异步机制带来的数据可能不同步问题
2、返回结果只能是一个值所以要详细设计返回结果类型
3、要注意Java引用传递和JavaScript值传递的差异
4、连续多次后台请求尽量采用批量调用(一个批量方法调用以DWREngine.beginBatch()开始WREngine.endBatch()结束.当DWREngine.endBatch()被调用时就说明开始调用批量方法,DWR就将这些方法打包在一起作为一次请求发送给服务器.)

5、尽量将JavaScript的逻辑处理代码抽取成一个独立的文件

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