（三）Struts2 拦截器

所有的学习我们必须先搭建好Struts2的环境（1、导入对应的jar包，2、web.xml，3、struts.xml）

第一节：拦截器简介　

　　　　（百度百科Struts2）

　　　　Struts2 拦截器是在访问某个Action 或Action 的某个方法，字段之前或之后实施拦截，并且Struts2 拦截器是可
　　　　插拔的，拦截器是ＡＯＰ的一种实现．
　　　　优点：通用功能的封装，提供了可重用性；

第二节：Struts2 预定义拦截器&拦截器栈

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7 
 8   <package name="manage" namespace="/" extends="struts-default">
 9       
10       <interceptors>
11           <interceptor name="myInterceptor" class="com.wishwzp.interceptor.MyInterceptor"></interceptor>
12       </interceptors>
13       
14       <action name="hello" class="com.wishwzp.action.HelloAction">
15           <result name="success">success.jsp</result>
16           
17           <interceptor-ref name="myInterceptor"></interceptor-ref>
18           <interceptor-ref name="defaultStack"></interceptor-ref>
19       </action>
20   </package>
21 
22 </struts>
struts.xml
 1 package com.wishwzp.interceptor;
 2 
 3 import com.opensymphony.xwork2.ActionInvocation;
 4 import com.opensymphony.xwork2.interceptor.Interceptor;
 5 
 6 public class MyInterceptor implements Interceptor{
 7 
 8     @Override
 9     public void destroy() {
10         // TODO Auto-generated method stub
11         System.out.println("MyInterceptor销毁");
12     }
13 
14     @Override
15     public void init() {
16         // TODO Auto-generated method stub
17         System.out.println("MyInterceptor初始化");
18     }
19 
20     @Override
21     public String intercept(ActionInvocation invocation) throws Exception {
22         System.out.println("在Action执行之前");
23         String result=invocation.invoke();
24         System.out.println("result:"+result);
25         System.out.println("在Action执行之后");
26         return result;
27     }
28 
29 }
MyInterceptor.java
 1 package com.wishwzp.action;
 2 
 3 import com.opensymphony.xwork2.ActionSupport;
 4 
 5 public class HelloAction extends ActionSupport{
 6 
 7     /**
 8      * 
 9      */
10     private static final long serialVersionUID = 1L;
11     
12     private String name;
13     
14     
15 
16     public String getName() {
17         return name;
18     }
19 
20     public void setName(String name) {
21         this.name = name;
22     }
23 
24     @Override
25     public String execute() throws Exception {
26         System.out.println("执行了HelloAction的默认方法");
27         return SUCCESS;
28     }
29     
30     
31 }
HelloAction.java
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 Name:${name }
11 </body>
12 </html>
success.jsp

url:http://localhost:8080/Struts2Chap03/hello?name=Struts2

我们需要注意的是在MyInterceptor.java中的：

String result=invocation.invoke();

第三节：自定义拦截器简单实例

我们在第二节中“MyInterceptor.java”中已经是自己定义的拦截器了

第四节：自定义拦截器-登录验证拦截器

 struts.xml
 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7 
 8   <package name="manage" namespace="/" extends="struts-default">
 9       
10       <interceptors>
11           <interceptor name="loginInterceptor" class="com.wishwzp.interceptor.LoginInterceptor"></interceptor>
12       </interceptors>
13       
14       <action name="user" class="com.wishwzp.action.UserAction">
15           <result name="success">success.jsp</result>
16           <result name="error">error.jsp</result>
17           <interceptor-ref name="defaultStack"></interceptor-ref>
18       </action>
19       
20       <action name="gril" class="com.wishwzp.action.GrilAction">
21           <result name="success">success.jsp</result>
22           <result name="error">error.jsp</result>
23           <interceptor-ref name="loginInterceptor"></interceptor-ref>
24           <interceptor-ref name="defaultStack"></interceptor-ref>
25       </action>
26   </package>
27 
28 </struts>
 User.java
 1 package com.wishwzp.model;
 2 
 3 public class User {
 4 
 5     private String userName;
 6     private String password;
 7     
 8     public String getUserName() {
 9         return userName;
10     }
11     public void setUserName(String userName) {
12         this.userName = userName;
13     }
14     public String getPassword() {
15         return password;
16     }
17     public void setPassword(String password) {
18         this.password = password;
19     }
20 }
 UserService.java
 1 package com.wishwzp.service;
 2 
 3 import com.wishwzp.model.User;
 4 
 5 public class UserService {
 6 
 7     public boolean login(User user){
 8         if("wishwzp".equals(user.getUserName())&&"123".equals(user.getPassword())){
 9             return true;
10         }else{
11             return false;
12         }
13     }
14 }
 UserAction.java
 1 package com.wishwzp.action;
 2 
 3 import java.util.Map;
 4 
 5 import com.wishwzp.model.User;
 6 import com.wishwzp.service.UserService;
 7 import com.opensymphony.xwork2.ActionContext;
 8 import com.opensymphony.xwork2.ActionSupport;
 9 
10 public class UserAction extends ActionSupport{
11 
12     /**
13      * 
14      */
15     private static final long serialVersionUID = 1L;
16     
17     private UserService userService=new UserService();
18     private User user;
19     private String error;
20 
21     public User getUser() {
22         return user;
23     }
24 
25     public void setUser(User user) {
26         this.user = user;
27     }
28 
29     public String getError() {
30         return error;
31     }
32 
33     public void setError(String error) {
34         this.error = error;
35     }
36 
37     @Override
38     public String execute() throws Exception {
39         if(userService.login(user)){
40             ActionContext actionContext=ActionContext.getContext();//获取上下文，去获取actionContext
41             Map<String, Object> session=actionContext.getSession();//通过actionContext去获取session
42             session.put("currentUser", user);//将用户存放在session中，就是放到了currentUser
43             return SUCCESS;//返回到SUCCESS
44         }else{
45             this.error="用户名或密码错误";
46             return "error";
47         }
48     }
49     
50     
51 }
 GrilAction.java
 1 package com.wishwzp.action;
 2 
 3 import com.opensymphony.xwork2.ActionSupport;
 4 
 5 public class GrilAction extends ActionSupport{
 6 
 7     /**
 8      * 
 9      */
10     private static final long serialVersionUID = 1L;
11     @Override
12     public String execute() throws Exception {
13         System.out.println("看美女");
14         return SUCCESS;
15     }
16     
17     
18 }
 LoginInterceptor.java
 1 package com.wishwzp.interceptor;
 2 
 3 import java.util.Map;
 4 
 5 import javax.servlet.http.HttpServletRequest;
 6 
 7 import org.apache.struts2.ServletActionContext;
 8 
 9 import com.opensymphony.xwork2.ActionContext;
10 import com.opensymphony.xwork2.ActionInvocation;
11 import com.opensymphony.xwork2.interceptor.Interceptor;
12 
13 public class LoginInterceptor implements Interceptor{
14 
15     @Override
16     public void destroy() {
17         // TODO Auto-generated method stub
18         System.out.println("LoginInterceptor销毁");
19     }
20 
21     @Override
22     public void init() {
23         // TODO Auto-generated method stub
24         System.out.println("LoginInterceptor初始化");
25     }
26 
27     @Override
28     public String intercept(ActionInvocation invocation) throws Exception {
29         System.out.println("在Action执行之前");
30         ActionContext actionContext=invocation.getInvocationContext();//获取actionContext，这样就可以获取session了
31         Map<String, Object> session=actionContext.getSession();//获取session
32         Object currentUser=session.get("currentUser");//获取前面的的用户有没有
33         String result=null;
34         if(currentUser!=null){
35             result=invocation.invoke();//不是空的话，说明已经登录过了
36         }else{//否则没有登录
37             //获取request
38             HttpServletRequest request=(HttpServletRequest)invocation.getInvocationContext().get(ServletActionContext.HTTP_REQUEST);
39             request.setAttribute("error", "请先登录！");
40             result="error";
41         }
42         System.out.println("result:"+result);
43         System.out.println("在Action执行之后");
44         return result;
45     }
46 
47 }
 login.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 <form action="user" method="post">
11     用户名：<input type="text" name="user.userName"/>
12     密码：<input type="password" name="user.password"/>
13     <input type="submit" value="登录"/>
14 </form>
15 </body>
16 </html>
 success.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 当前用户：${currentUser.userName }
11 </body>
12 </html>
 error.jsp
 1 <%@ page language="java" contentType="text/html; charset=UTF-8"
 2     pageEncoding="UTF-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 7 <title>Insert title here</title>
 8 </head>
 9 <body>
10 错误信息：${error }  <a href="login.jsp">登录</a>
11 </body>
12 </html>

url：http://localhost:8080/Struts2Chap03/login.jsp

url:http://localhost:8080/Struts2Chap03/gril

我们再上面的代码中优化一下strut.xml。

其他什么地方都不变

 struts.xml
 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE struts PUBLIC
 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
 4     "http://struts.apache.org/dtds/struts-2.0.dtd">
 5 
 6 <struts>
 7     
 8   
 9   <package name="manage" namespace="/" extends="struts-default">
10       
11       <interceptors>
12           <!-- 配置loginInterceptor拦截器 -->
13           <interceptor name="loginInterceptor" class="com.wishwzp.interceptor.LoginInterceptor"></interceptor>
14           
15           <!-- 拦截器栈 -->
16           <!-- 配置一个名为myStack的拦截器栈，里面有拦截器loginInterceptor和默认的拦截器 -->
17           <interceptor-stack name="myStack">
18               <interceptor-ref name="loginInterceptor"></interceptor-ref>
19               <interceptor-ref name="defaultStack"></interceptor-ref>
20           </interceptor-stack>
21       </interceptors>
22       
23       <!-- 配置使用自己配置的默认拦截器myStack -->
24       <default-interceptor-ref name="myStack"></default-interceptor-ref>
25       
26       <!-- 使用全局错误信息，就不需要去一个个写error了 ，所有的action都会找到这个全局error的-->
27       <global-results>
28           <result name="error">error.jsp</result>
29       </global-results>
30       
31       <action name="user" class="com.wishwzp.action.UserAction">
32           <result name="success">success.jsp</result>
33           
34           <!-- 这个默认拦截器栈这里必须有，不然的话这里的登录也被拦截掉了 -->
35           <interceptor-ref name="defaultStack"></interceptor-ref>
36       </action>
37       
38       <action name="gril" class="com.wishwzp.action.GrilAction">
39           <result name="success">success.jsp</result>
40       </action>
41   </package>
42 
43 </struts>
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原文地址：https://www.cnblogs.com/wishwzp/p/5470955.html