struts2拦截器（二）

一.理解拦截器

1. 拦截器是在防问某个方法，字段之前或之后实施拦截，并且拦截器是可插拔的，拦截器是ＡＯＰ的一种实现．

2. 拦截器栈（Interceptor Stack）。拦截器栈就是将拦截器按一定的顺序联结成一条链。在访问被拦截的方法或字段时，拦截器链中的拦截器就会按其之前定义的顺序被调用。

二.实现原理
Struts2拦截器的实现原理相对简单，当请求struts2的action时，Struts 2会查找配置文件，并根据其配置实例化相对的拦截器对象，然后串成一个列表，最后一个一个地调用列表中的拦截器

三.拦截器的配置
1. 普通的拦截器

xml代码(即stuts的配置文件)

1 < package name = " default " extends = " struts-default " > 
2
3
4 < interceptors > 
5
6
7 < interceptor name = " 拦截器名1 " class = " 拦截器实现类 " /> 
8
9
10 < interceptor name = " 拦截器名2 " class = " 拦截器实现类 " /> 
11
12
13 </ interceptors > 
14
15
16 < action name = " login " 　 class = " com.Logon " > 
17
18
19 　　 < interceptor - ref name = " defaultStack " /> 
20
21
22 < interceptor - ref name = " 拦截器名1 " /> 
23
24
25 < interceptor - ref name = " 拦截器名2 " /> 
26
27
28 < result name = " input " > logon.jsp </ result > 
29
30
31 < result name = " success " >/ index.jsp </ result > 
32
33
34 </ action > 
35
36
37 </ package >

2. 拦截器栈

1 package name = " default " extends = " struts-default " > 
2
3
4 < interceptors > 
5
6
7 < interceptor name = " 拦截器名1 " class = " 拦截器实现类 " /> 
8
9
10 < interceptor name = " 拦截器名2 " class = " 拦截器实现类 " /> 
11
12
13 < interceptor - stack name = " myStack " > 
14
15
16 < interceptor - ref name = " 拦截器名1 " /> 
17
18
19 < interceptor - ref name = " 拦截器名2 " /> 
20
21
22 </ interceptor - stack > 
23
24
25 </ interceptors > 
26
27
28 < action name = " login " class = " com.Logon " > 
29
30
31 　　　　　 < interceptor - ref name = " defaultStack " /> 
32
33
34 < interceptor - ref name = " myStack " /> 
35
36
37 < result name = " input " > login.jsp </ result > 
38
39
40 < resultnameresultname = " success " >/ index.jsp </ result > 
41
42
43 </ action > 
44
45
46 </ package >

需要注意的是，如果为Action指定了一个拦截器，则系统默认的拦截器栈将会失去作用。为了继续使用默认拦截器，所以上面配置文件中手动引入了默认拦截器.

四.自定义拦截器
 1.直接或间接实现接口com.opensymphony.xwork2.interceptor.Interceptor。
 2.或者继承类com.opensymphony.xwork2.interceptor.AbstractInterceptor
 3.通过<interceptor>元素来定义拦截器
 4.通过<interceptor-ref>元素来使用拦截器

五.使用拦截器实现权限控制
1.功能
使用自定义拦截器来完成用户权限的控制，当执行操作时，判断用户是否己经登陆，如果没有登陆跳转到登陆页面

2.拦截器类

java代码

1 package com.interceptor;
2 
3 import com.opensymphony.xwork2.Action;
4 import com.opensymphony.xwork2.ActionContext;
5 import com.opensymphony.xwork2.ActionInvocation;
6 import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
7 
8 public class AuthorizationInterceptor extends AbstractInterceptor {
9 
10 private static final long serialVersionUID = 1L ;
11 
12  @Override
13 public String intercept(ActionInvocation actionInvocation) throws Exception {
14 
15 ActionContext actionContext = actionInvocation.getInvocationContext();
16 
17 Object user = actionContext.get("user" );
18 
19 if(user != null ){
20 return actionInvocation.invoke();
21 } else {
22 actionInvocation.getInvocationContext().put("nav_title", "你还没有登陆,请先登陆" );
23 return Action.LOGIN;
24 }
25 }
26 
27  }
28

2.配置
Xml代码

1 <?xml version="1.0" encoding="UTF-8" ?> 
2
3
4 <!DOCTYPE struts PUBLIC 
5
6
7 "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" 
8
9
10 "http://struts.apache.org/dtds/struts-2.0.dtd"> 
11
12 <struts> 
13 <package name="user" extends="struts-default">
14
15 <interceptors>
16 
17 <interceptor name="authority" class="com.interceptor.AuthorizationInterceptor"></interceptor>
18 </interceptors> 
19
20 <action name="user" class="com.UserAction"> 
21 
22 <interceptor-ref name="authority"/>
23 <interceptor-ref name="defaultStack"/>
24 <result name="succee">/logon/welcome.jsp</result> 
25 <result name="login">/logon/logon.jsp</result>
26 </action>
27 </package>
28 </struts> 

访问http://localhost:8080/struts2-interceptor/user.action时，会判断用户是否登陆

六.方法拦截器
1.Struts2提供MethodFilterInterceptor类，该类是AbstractInerceptor的子类，可以实现对Action方法的拦截.
2. MethodFilterInterceptor中有两个方法
　 setExcludeMethods:排除需要过滤的方法
setIncludeMethods:设置需要过滤的方法
如果一个方法同时在excludeMethods和includeMethods中出现,则会被拦截

3.实现拦截器
Java代码

1 package com.interceptor;
2 
3 import com.opensymphony.xwork2.ActionInvocation;
4 import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;
5 
6 public class LogInterceptor extends MethodFilterInterceptor {
7 
8 private static final long serialVersionUID = 1L ;
9 
10 private String name;
11 
12 @Override
13 protected String doIntercept(ActionInvocation actionInvocation) throws Exception {
14 
15 System.out.println( " 拦截器名称: " + name);
16 System.out.println( " action: " + actionInvocation.getAction());
17 
18 return actionInvocation.invoke();
19 }
20 
21 public String getName() {
22 return name;
23 }
24 
25 public void setName(String name) {
26 this .name = name;
27 }
28 }
29

Java代码

1 package com; 
2 public class ManageAction { 
3 public String execute(){
4 System.out.println( " execute

. " ); 
5 return " succee " ;
6 } 
7
8 public String search(){ 
9 System.out.println( " search

. " );
10          return " succee " ;
11     }
12      public String add(){
13         System.out.println( " add

. " );
14 return " succee " ;
15 }
16 } 
17

struts.xml配置

1 < action name = " manage " class = " com.ManageAction " > 
2 < interceptor - ref name = " log " > 
3 < param name = " name " > 日志拦截 </ param > 
4 
5
6 < param name = " includeMethods " > execute,add </ param > 
7  
8 < param name = " excludeMethods " > search,execute </ param >
9 </ interceptor - ref > 
10 < result name = " succee " >/ welcome.jsp </ result >
11 </ action >
12

打开浏览器访问　http://localhost:8080/struts2-interceptor/manage.action

会报执行execute方法，会执行拦截器
拦截器名称:日志拦截
action:com.ManageAction@1a0ae6d
execute....

当访问 http://localhost:8080/struts2-interceptor/manage!search.action
执行search方法，不会执行拦截器

struts2拦截器（二）

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