什么是与Servlet API解耦？

为了避免与servlet API耦合在一起，方便Action做单元测试，

Struts2对HttpServletRequest，HttpSession，和ServletContext进行了封装，构造了3个Map对象来替代这三个对象，在Action中可以直接使用HttpServletRequest，HttpSession，ServletContext对应的Map对象来保存和读取数据。

两种解耦方式：

1、    使用Struts2提供的工具类中提供的静态方法，得到对用的封装后对象。

　　

package cn.itcast.context;

import java.util.Map;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

public class ContextAction extends ActionSupport {

    /**

     *

     */

    private static final long serialVersionUID = 1L;

    public String test() throws Exception{

        System.out.println("ContextAction ****** test()");

        HttpServletRequest request=ServletActionContext.getRequest();

        request.setAttribute("username","username_request");

        HttpServletResponse response=ServletActionContext.getResponse();

        Map sessionMap=ServletActionContext.getContext().getSession();

        sessionMap.put("username", "username_session");

        ServletContext sc=ServletActionContext.getServletContext();

        sc.setAttribute("username", "username_application");

        return "attr";

    }

}

2、    Action实现ServletRequestAware，ServletResponseAware，ServletContextAware，SessionAware四个接口，分别重写对应的set方法，达到操作该4个封装后对象。

package cn.itcast.context;

import java.util.Map;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import org.apache.struts2.ServletActionContext;

import org.apache.struts2.interceptor.ServletRequestAware;

import org.apache.struts2.interceptor.ServletResponseAware;

import org.apache.struts2.interceptor.SessionAware;

import org.apache.struts2.util.ServletContextAware;

import com.opensymphony.xwork2.ActionSupport;

public class Context02Action extends ActionSupport

    implements ServletRequestAware,ServletResponseAware,ServletContextAware,SessionAware{

    HttpServletRequest request;

    HttpServletResponse response;

    ServletContext context;

    Map<String, Object> sessionMap;

    private static final long serialVersionUID = 1L;

    public String test() throws Exception{

        System.out.println("ContextAction ****** test()");

        HttpServletRequest request=ServletActionContext.getRequest();

        request.setAttribute("username","username_request");

        HttpServletResponse response=ServletActionContext.getResponse();

        Map sessionMap=ServletActionContext.getContext().getSession();

        sessionMap.put("username", "username_session");

        ServletContext sc=ServletActionContext.getServletContext();

        sc.setAttribute("username", "username_application");

        return "attr";

    }

    public void setSession(Map<String, Object> session) {

        this.sessionMap=session;

    }

    public void setServletContext(ServletContext context) {

        this.context=context;

    }

    public void setServletResponse(HttpServletResponse response) {

        this.response=response;

    }

    public void setServletRequest(HttpServletRequest request) {

        this.request=request;

    }

}

两种方式没有好坏之分，全凭个人喜好！

其他代码：

<?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="context" namespace="/context" extends="struts-default">

         <action name="contextAction_test" class="cn.itcast.context.ContextAction" method="test">

             <result name="success">/context/success.jsp</result>

             <result name="attr">/context/attr.jsp</result>

         </action>

         <action name="contextAction02_test" class="cn.itcast.context.Context02Action" method="test">

             <result name="success">/context/success.jsp</result>

             <result name="attr">/context/attr.jsp</result>

         </action>

     </package>

</struts>

struts_context.xml

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<%

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>My JSP 'test.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">

    <meta http-equiv="cache-control" content="no-cache">

    <meta http-equiv="expires" content="">

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

    <meta http-equiv="description" content="This is my page">

    <!--

    <link rel="stylesheet" type="text/css" href="styles.css">

    -->

  </head>

  <body>

    <a href="${pageContext.request.contextPath }/context/contextAction_test.do">textContext</a><br/>

    <a href="${pageContext.request.contextPath }/context/contextAction02_test.do">testContext</a><br/>

  </body>

</html>

context/test.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<%

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>My JSP 'success.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">

    <meta http-equiv="cache-control" content="no-cache">

    <meta http-equiv="expires" content="">

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

    <meta http-equiv="description" content="This is my page">

    <!--

    <link rel="stylesheet" type="text/css" href="styles.css">

    -->

  </head>

  <body>

    xxxxxxxxxxxxxx<br/>

  </body>

</html>

context/success.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%@ taglib prefix="s" uri="/struts-tags" %>

<%

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>My JSP 'attr.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">

    <meta http-equiv="cache-control" content="no-cache">

    <meta http-equiv="expires" content="">

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

    <meta http-equiv="description" content="This is my page">

    <!--

    <link rel="stylesheet" type="text/css" href="styles.css">

    -->

  </head>

  <body>

    ${requestScope.username }<br/>

    ${sessionScope.username }<br/>

    ${applicationScope.username }

  </body>

</html>

context/attr.jsp

　　

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