struts2基础——需要注意的几点
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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。
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