Action类的三种编写方式（七）
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2022-05-07 21:53:03
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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>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;
}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 {
@Override
public 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>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;
@Override
public 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>