Action类的三种编写方式（七）

1. Action类就是一个POJO类什么是POJO类，POJO（Plain Ordinary Java Object）简单的Java对象.简单记：没有继承某个类，没有实现接口，就是POJO的类。2. Action类可以实现Action接口* Action接口中定义了5个常量，5个常量的值对应的是5个逻辑视图跳转页面（跳转的页面还是需要自己来配置），还定义了一个方法，execute方法。* 大家需要掌握5个逻辑视图的常量* SUCCESS-- 成功.* INPUT-- 用于数据表单校验.如果校验失败,跳转INPUT视图.* LOGIN-- 登录.* ERROR-- 错误.* NONE-- 页面不转向.3. Action类可以去继承ActionSupport类（开发中这种方式使用最多）* 设置错误信息

supportAction里面提供了一些属性的方法供我们使用。

举例：

1.POJO

package com.ken.action;public class Demo1Action {/** * execute是默认方法 * return null; 不会进行跳转 * @return */public String execute(){System.out.println("Demo1Action就是POJO类...");return null;}}

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN""http://struts.apache.org/dtds/struts-2.3.dtd"><struts><package name="default" namespace="/" extends="struts-default"><!-- 配置Action --><action name="hello" class="com.ken.action.HelloAction" method="sayHello"><!-- 配置跳转的页面，路径的写法：在struts2框架中，不管是转发还是重定向都不用写项目名 --><!-- name中的ok叫做逻辑视图名称 --><result name="ok">/demo1/success.jsp</result></action><!-- POJO --><action name="demo1Action" class="com.ken.action.Demo1Action"></action></package></struts>

执行结果:

2.实现Action接口

/* * Copyright 2002-2007,2009 The Apache Software Foundation. *  * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at *  *      http://www.apache.org/licenses/LICENSE-2.0 *  * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.opensymphony.xwork2;/** * All actions <b>may</b> implement this interface, which exposes the <code>execute()</code> method. * <p/> * However, as of XWork 1.1, this is <b>not</b> required and is only here to assist users. You are free to create POJOs * that honor the same contract defined by this interface without actually implementing the interface. */public interface Action {    /**     * The action execution was successful. Show result     * view to the end user.     */    public static final String SUCCESS = "success";    /**     * The action execution was successful but do not     * show a view. This is useful for actions that are     * handling the view in another fashion like redirect.     */    public static final String NONE = "none";    /**     * The action execution was a failure.     * Show an error view, possibly asking the     * user to retry entering data.     */    public static final String ERROR = "error";    /**     * The action execution require more input     * in order to succeed.     * This result is typically used if a form     * handling action has been executed so as     * to provide defaults for a form. The     * form associated with the handler should be     * shown to the end user.     * <p/>     * This result is also used if the given input     * params are invalid, meaning the user     * should try providing input again.     */    public static final String INPUT = "input";    /**     * The action could not execute, since the     * user most was not logged in. The login view     * should be shown.     */    public static final String LOGIN = "login";    /**     * Where the logic of the action is executed.     *     * @return a string representing the logical result of the execution.     *         See constants in this interface for a list of standard result values.     * @throws Exception thrown if a system level exception occurs.     *                   <b>Note:</b> Application level exceptions should be handled by returning     *                   an error value, such as <code>Action.ERROR</code>.     */    public String execute() throws Exception;}

这是Action的源码，其实，和自己定义一个接口没什么区别。

package com.ken.action;import com.opensymphony.xwork2.Action;/** * 实现Action接口，Action是框架提供的接口 */public class Demo2Action implements Action {@Overridepublic String execute() throws Exception {System.out.println("实现了Action接口");return SUCCESS;}}

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN""http://struts.apache.org/dtds/struts-2.3.dtd"><struts><package name="default" namespace="/" extends="struts-default"><!-- 配置Action --><action name="hello" class="com.ken.action.HelloAction" method="sayHello"><!-- 配置跳转的页面，路径的写法：在struts2框架中，不管是转发还是重定向都不用写项目名 --><!-- name中的ok叫做逻辑视图名称 --><result name="ok">/demo1/success.jsp</result></action><!-- POJO --><action name="demo1Action" class="com.ken.action.Demo1Action"></action><!-- 实现Action接口 --><action name="demo2Action" class="com.ken.action.Demo2Action"><result name="success">/demo1/success.jsp</result></action></package></struts>

运行效果：

三、Action类继承ActionSupport

package com.ken.action;import com.opensymphony.xwork2.ActionSupport;/** * 编写Action类继承ActionSupport，ActionSupport已经实现了Action和一些其他的类 * */public class Demo3Action extends ActionSupport {private static final long serialVersionUID = -1796731178213647676L;@Overridepublic String execute() throws Exception {System.out.println("Demo3Action继承了ActionSupport类");return NONE;}}

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN""http://struts.apache.org/dtds/struts-2.3.dtd"><struts><package name="default" namespace="/" extends="struts-default"><!-- 配置Action --><action name="hello" class="com.ken.action.HelloAction" method="sayHello"><!-- 配置跳转的页面，路径的写法：在struts2框架中，不管是转发还是重定向都不用写项目名 --><!-- name中的ok叫做逻辑视图名称 --><result name="ok">/demo1/success.jsp</result></action><!-- POJO --><action name="demo1Action" class="com.ken.action.Demo1Action"></action><!-- 实现Action接口 --><action name="demo2Action" class="com.ken.action.Demo2Action"><result name="success">/demo1/success.jsp</result></action><!-- Action类继承ActionSupport --><action name="demo3Action" class="com.ken.action.Demo3Action"></action></package></struts>

运行效果：

源码下载