struts2基础——需要注意的几点

struts是流行和成熟的基于MVC设计模式的web应用程序框架，使用struts可以帮助我们减少运用MVC设计模型来开发web应用的时间。

目录：

一、struts2的工作原理及文件结构

二、三种访问Servlet API的方式

三、struts接收参数的三种方式

四、自定义拦截器

一、struts2的工作原理及文件结构

注：FilterDispatcher被替成StrutsPrepareAndExecuteFilter（如果使用FilterDispatcher过滤器时，程序员自己写的Filter过滤器必须放在所有过滤器的前面。而StrutsPrepareAndExecuteFilter过滤器可以让程序员在执行action之前写自己的Filter）

描述Struts流程：

网页产生HttpServletRequest请求->经过多个过滤器->到达ActionMaaper，判断是否是action请求（如果是）->通过StrutsPrepareAndExecuteFilter过滤器到达Actionproxy，一方面通过configuration Manager（配置管理器）读取struts.xml文档，另一方面创建一个实例，经过一系列的拦截器->执行到Action->返回result(对应了视图)->经过一系列的拦截器（逆序）->通过HttpServletResponse返回到用户实例。

二、三种访问servlet API的方法

struts2中没有提供任何一个servlet对象，不存在HttpServletRequest，HttpServletResponse对象。但是Struts2提供了三种方式间接的去访问Servlet API

1、ActionContext

通过ActionContext的getContext()静态方法获取ActionContext对象，通过ActionContext对象的一些getSession(),getApplication(),put()等方法，但是千万要注意的是，get获取到的对象都为Map键值对类型。com.opensymphony.xwork2.ActionContext

public String execute() {
        if ("ping".equals(username)) {
            /*
             * ActionContext可以获得Servlet对象 但是无法获得response响应对象获得
             * 获得的request、session、Application 都是Map类型
             */

            ActionContext.getContext().put("用户名", username);
            Map session=ActionContext.getContext().getSession();
            Map application=ActionContext.getContext().getApplication();
            Map request=(Map)ActionContext.getContext().get(StrutsStatics.HTTP_REQUEST);
        } else {
            ActionContext.getContext().put("info", "信息");
        }
        return SUCCESS;
    }

2、ServletActionContext

通过调用ServletActionContext类的一些包括getResponse(),getRequest(),getServletContext()等在内的静态方法，这些静态方法的返回类型是和Servlet中的对象类型是一一对应的。其中getResponse()返回类型为HttpServletResponse，getRequest()返回类型为HttpServletRequest().

public String execute2() throws IOException {
        if ("ping".equals(username)) { 
            HttpServletResponse response=ServletActionContext.getResponse();
 4             HttpServletRequest request=ServletActionContext.getRequest();
            HttpSession session=ServletActionContext.getRequest().getSession();
            ServletContext application=ServletActionContext.getServletContext();
        } else {
            
        }
        System.out.println(username);
        return SUCCESS;
    }

3、实现xxxAware接口

（1）实现ServletRequestAware，ServletResponseAware，ServletSessionAware  

public class LoginAction extends ActionSupport implements ServletRequestAware


private HttpServletRequest request;
//需实现方法 public void setServletRequest(HttpServletRequest request) { this.request=request; } //response示例
public String execute1() throws IOException {
        if ("ping".equals(username)) {
            response.setContentType("text/html;charset=utf-8");   
            PrintWriter out = response.getWriter();   
            out.print("<script type='text/javascript'>alert('验证码输入错误!')</script>");   
            out.print("<script type='text/javascript'>location.href='/index.jsp'</script>");   
            out.flush();   
            out.close();  
        } else {
            response.setContentType("text/html;charset=utf-8");   
            PrintWriter out = response.getWriter();   
            out.print("<script type='text/javascript'>alert('验证码输入错误!')</script>");   
            out.flush();   
            out.close();  
        }
        System.out.println(username);
        return SUCCESS;
    }

（2）实现RequestWare、SessionWare、ApplicationWare等接口


public class LoginAction2 extends ActionSupport implements RequestAware,SessionAware, ApplicationAware {
    
    private Map<String, Object> request;
    private Map<String, Object> session;
    private Map<String, Object> application;
    
    //DI dependency injection
    //IoC inverse of control
    public String execute() {
        request.put("r1", "r1");
        session.put("s1", "s1");
        application.put("a1", "a1");
        return SUCCESS; 
    }

    @Override
    public void setRequest(Map<String, Object> request) {
        this.request = request;
    }

    @Override
    public void setSession(Map<String, Object> session) {
        this.session = session;
    }

    @Override
    public void setApplication(Map<String, Object> application) {
        this.application = application;
    }
    
    
}

三、struts三种接收参数方式

Struts有三种方式接收参数，且这三种方式都是自动完成赋值的setter方法。

1、使用Action的属性接收参数

代码：

struts.xml

<?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">
  <action name="LoginAction" method="login" class="com.third.LoginAction1">
    <result>/loginSuccess.jsp</result>
  </action>
</package>


</struts>

login.jsp(登陆提示页面）

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>login page</h1>
    <form action="LoginAction.action" method="post">
       <table>
          <tr>
             <td>username:</td>
             <td><input type="text" name="username"/></td>
          </tr>
           <tr>
             <td>password:</td>
             <td><input type="password" name="password"/></td>
          </tr>
       
          <tr> 
             <td><input type="submit" value="submit"></td>
             <td><input type="reset" value="reset"></td>
          </tr>
          
       </table>
    
    </form>
</body>
</html>

loginSuccess.jsp（登陆成功提示界面）

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>login success!</title>
</head>
<body>
<h1>login success!</h1>
</body>
</html>

LoginAction.java

package com.third;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction1 extends ActionSupport {

    private String username;
    private String password;
    
    public String login(){
        //这里能够打印出来传入的值，则说明能够自动调用setter方法完成赋值
        System.out.println("username:"+username+"  password:"+password);
        return SUCCESS;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
    
}

运行结果截图：

2、使用DomainModel接收参数

注：这里在表单传值是，必须指明这个属性值，到底穿个action中的那个引用，例如user.username.

代码：

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
   
   <package name="default" namespace="/" extends="struts-default">
      <action name="LoginAction" method="login" class="com.third.LoginAction">
        <result>/loginSuccess.jsp</result>
      </action>
   </package>
  
</struts>  

login.jsp

<%@ 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>My JSP 'login.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
  <h1>login page!</h1>
   <form action="LoginAction.action" method="post">
       <table>
          <tr>
             <td>username:</td>
             <td><input type="text" name="user.username"/></td>
          </tr>
           <tr>
             <td>password:</td>
             <td><input type="password" name="user.password"/></td>
          </tr>
       
          <tr> 
             <td><input type="submit" value="submit"></td>
             <td><input type="reset" value="reset"></td>
          </tr>       
       </table>   
    </form>
  </body>
</html>

loginSuccess.jsp

<%@ 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>My JSP 'loginSuccess.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
      <h1>login success!</h1>
  </body>
</html>

User.java

package com.third;

public class User {

    private String username;
    private String password;
    
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }    
}

LoginAction.java

package com.third;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.inject.Context;

public class LoginAction extends ActionSupport {

    private User user;
    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
    public String login(){
          //这里可以打印出传入的值的话，Action完成了自动调用setter方法赋值
        System.out.println("username:"+user.getUsername()+" password:"+this.getUser().getPassword());
        return SUCCESS;
    }
    
}

运行结果截图：

3、使用ModelDriven接受参数

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
   
   <package name="default" namespace="/" extends="struts-default">
      <action name="LoginAction" method="login" class="com.third.LoginAction">
        <result>/loginSuccess.jsp</result>
      </action>
   </package>
  
</struts>    

login.jsp

<%@ 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>My JSP 'login.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
  <h1>login page!</h1>
   <form action="LoginAction.action" method="post">
       <table>
          <tr>
             <td>username:</td>
             <td><input type="text" name="username"/></td>
          </tr>
           <tr>
             <td>password:</td>
             <td><input type="password" name="password"/></td>
          </tr>
       
          <tr> 
             <td><input type="submit" value="submit"></td>
             <td><input type="reset" value="reset"></td>
          </tr>       
       </table>   
    </form>
  </body>
</html>

loginSuccess.jsp

<%@ 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>My JSP 'loginSuccess.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
      <h1>login success!</h1>
  </body>
</html>

User.java

package com.third;

public class User {

    private String username;
    private String password;
    
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }    
}

LoginAction.java

package com.third;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;
import com.opensymphony.xwork2.inject.Context;

public class LoginAction extends ActionSupport implements ModelDriven<User> {

    private User user=new User();
    public String login(){
      //这里打印出传入的参数值，说明自动调用setter方法赋值
        System.out.println("username:"+user.getUsername()+" password:"+user.getPassword());
        return SUCCESS;
    }

    @Override
    public User getModel() {
        
        return user;
    }
    
}

运行结果截图：

四、自定义拦截器

注：特别要注意在使用拦截的器的时候，使用表单传值，会导致Action中获得的属性的值为null，或是其他的默认的初始化值。

1、实现Interceptor接口

-void init()方法：初始化拦截器所需要的资源

-void destory()方法：释放init()中分配的资源

-String intercept(ActionInvocation invocation)throws Exception:实现拦截器功能，利用ActionInvocation参数获取Action状态，返回result字符串作为逻辑视图。

代码：

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>

   
   <package name="default" namespace="/" extends="struts-default">
   <!--注册拦截器  -->
      <interceptors>
         <interceptor name="timefigureFilter" class="com.third.TimeInterceptor">
         </interceptor>
      </interceptors>
   
   
      <action name="LoginAction" method="login" class="com.third.LoginAction">
        <result>/loginSuccess.jsp</result>
        <interceptor-ref name="timefigureFilter"></interceptor-ref>
      </action>
   </package>
  
</struts>    

login.jsp

<%@ 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>My JSP 'login.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
  <h1>login page!</h1>
   <form action="LoginAction.action" method="post">
       <table>
          <tr>
             <td>username:</td>
             <td><input type="text" name="username"/></td>
          </tr>
           <tr>
             <td>password:</td>
             <td><input type="password" name="password"/></td>
          </tr>
       
          <tr> 
             <td><input type="submit" value="submit"></td>
             <td><input type="reset" value="reset"></td>
          </tr>       
       </table>   
    </form>
  </body>
</html>

loginSuccess.jsp

<%@ 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>My JSP 'loginSuccess.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>
  
  <body>
      <h1>login success!</h1>
  </body>
</html>

User.java

package com.third;

public class User {

    private String username;
    private String password;
    
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }    
}

TimeInterceptor.java

package com.third;

import javax.servlet.http.HttpServletRequest;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.Interceptor;

public class TimeInterceptor implements Interceptor {

    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    @Override
    public void init() {
        // TODO Auto-generated method stub

    }

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        HttpServletRequest request=ServletActionContext.getRequest();
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        request.setAttribute("username", username);
        //1执行action之前
        long start=System.currentTimeMillis();
        //2执行下一个拦截器，直到最后一个拦截器，则执行目标Action
        String result=invocation.invoke();
        //3执行完action之后
        long end=System.currentTimeMillis();
        System.out.println("执行Action花费的时间为："+(end-start)+"ms");
        return result;
    }

}

LoginAction.java

package com.third;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;
import com.opensymphony.xwork2.inject.Context;

public class LoginAction extends ActionSupport implements ModelDriven<User> {

    private User user=new User();
    public String login(){
           //着重看着两行代码运行打印的结果
        System.out.println("username:"+user.getUsername());
           //System.out.println("username:"+ServletContext.getRequest().getAttribute("username");//这里也可完成正常的获值
        System.out.println("username:"+ServletActionContext.getRequest().getAttribute("username"));
        return SUCCESS;
    }

    @Override
    public User getModel() {
        
        return user;
    }
    
}

运行结果截图：

注：注意看结果，打印的第一个username的属性值为null，而第二个为表单填写的dasd。这里涉及到拦截器的使用导致的表单传值问题。

分析：拦截器的使用导致的表单传值问题

原因：登陆界面填写完成之后，表单需要实现页面跳转，而这些将会交给struts，struts在调用action的过程其实是调用action中的struts.xml配置action标签method属性指定的方法（默认是execute()）,而在调用这个方法前会对表单的属性信息将会别匹配赋值给action中同名属性。正常情况下没有自定义的拦截器，通过表单传递的属性值没有问题。

要完成这个功能，有很大程度上， Struts 2 要依赖与 ValueStack 对象。这个对象贯穿整个 Action 的生命周期 (每个 Action 类的对象实例会拥有一个 ValueStack 对象 ) 。当 Struts 2 接收到一个 action 的请求后，会先建立Action 类的对象实例，但不会调用 Action 方法，而是先将 Action 类的相应属性放到 ValueStack 对象的顶层节点(ValueStack 对象相当于一个栈 ). 只是所有的属性值都是默认的值，如 String 类型的属性值为 null,int 类型的属性值为 0 等。

   在处理完上述工作后， Struts 2 就会调用拦截器链中的拦截器，当调用完所有的拦截器后，最后会调用 Action 类的 Action 方法，在调用 Action 方法之前，会将 ValueStack 对象顶层节点中的属性值赋给 Action 类中相应的属性。大家要注意，在这里就给我们带来了很大的灵活性。也就是说，在 Struts 2 调用拦截器的过程中，可以改变ValueStack 对象中属性的值，当改变某个属性值后， Action 类的相应属性值就会变成在拦截器中最后改变该属性的这个值。

好多废话~总结就是：在拥有自定义的过滤器时，表单传属性值会先赋值给Action中属性，当运行完过滤器时，才会调用Action中的方法，在调用之前会将 ValueStack 对象中的默认初始化值赋给action中的属性，然后调用action中的方法，这样action中的属性全是ValueStack 对象中的默认初始化值。

解决的方法：间接访问Servlet的API，通过request对象去访问属性和属性值。如：

HttpServletRequest request=ServletActionContext.getRequest();

String username=request.getParameter("username");

2、方式二：继承AbstractInterceptor类

-提供了init()和destroy()方法的实现

-只需要实现intercept()方法即可

代码：

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>

   
   <package name="default" namespace="/" extends="struts-default">
   <!--注册拦截器  -->
      <interceptors>       
          <interceptor name="timefigureFilter1" class="com.third1.TimeInterceptor">
         </interceptor>
      </interceptors>
      
       <action name="TimeAction" class="com.third1.TimeAction">
        <result>/index.jsp</result>
        <!--引用拦截器  -->
        <interceptor-ref name="timefigureFilter1"></interceptor-ref>
      </action>
      
   </package>
  
</struts>    

TimeInterceptor.java

package com.third1;

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class TimeInterceptor extends AbstractInterceptor {

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        //1.执行action之前
        long start=System.currentTimeMillis();
        //2.执行下一个拦截器，如果已经是最后一个拦截器，则执行目标Action
        
        ServletActionContext.getRequest().setAttribute("username", "小帅哥");
        ServletActionContext.getRequest().getSession().setAttribute("username","小美女");
        ServletActionContext.getServletContext().setAttribute("username", "少艾");
        String result=invocation.invoke();
        //3.执行Action之后
        long end=System.currentTimeMillis();
        System.out.println("执行Action花费的时间："+(end-start)+"ms");
        //获取request对象，调用其setAttribute函数，将时间作为属性保存到request对象中
        ServletActionContext.getRequest().setAttribute("time", (end-start));
        ServletActionContext.getRequest().getSession().setAttribute("time1",(end-start));
        ServletActionContext.getServletContext().setAttribute("time2", (end-start));
        return result;
    }

}

TimeAction.java

package com.third1;

import com.opensymphony.xwork2.ActionSupport;

public class TimeAction extends ActionSupport {

    @Override
    public String execute() throws Exception{
        
        for(int i=0;i<3;i++){
            Thread.sleep(1000);
        }
        return SUCCESS;
    }
}

index.jsp

<%@ 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>My JSP 'index.jsp' starting page</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">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>
  
  <body>
   
   <h1>执行Action用户名：<%=request.getAttribute("username") %>（通过request方式获取）</h1>
   <h1>执行Action用户名：<%=session.getAttribute("username") %>（通过session方式获取）</h1>
   <h1>执行Action用户名：<%=application.getAttribute("username") %>（通过application方式获取）</h1>
  
   <h1>执行Action花费的时间：<%=request.getAttribute("time") %>（通过request方式获取）</h1>
   <h1>执行Action花费的时间：<%=session.getAttribute("time1") %>（通过session方式获取）</h1>
   <h1>执行Action花费的时间：<%=application.getAttribute("time2") %>（通过application方式获取）</h1>
  </body>
</html>

运行结果截图：

分析：对比两种颜色标记的代码区，对比一下他们，并且结合结果进行分析。我们不难发现过滤器的调用分为两个阶段，第一个阶段是在产生HttpServletRequest请求之后、action方法调用之前；第二阶段是产生与action之后，jsp页面（Template显示）跳转之后，HttpServletResponse之前。所以当你在 String result=invocation.invoke();   这条语句之后通过request，application，session给它设置属性值，将会没有起到任何作用。

可以结合struts2的工作原理及文件结构图进行参考。