Struts2拦截器介绍

一、拦截器简介

Struts拦截器和Action的关系如图：

为了在使用拦截器时制定参数值，应通过<interceptor-ref …/>元素添加<param …/>子元素来为拦截器指定参数值。下面是配置拦截器动态指定参数值的语法。

  1: <interceptor-stack name="拦截器栈一">
  2:     <interceptor-ref name="拦截器一">
  3:         <param name="参数一">参数值一</param>
  4:         <param name="参数二">参数值二</param>
  5:     </interceptor-ref>
  6: </interceptor-stack>

二、自定义拦截器

1、简单的拦截器

用户要开发自己的拦截器，需要实现com.opensymphony.xwork2.interceptor.Interceptor接口。下面实现了一个简单的拦截器

1、SimpleInterceptor.java

  1: package cc.openhome;
  2: import java.util.Date;
  3: import com.opensymphony.xwork2.ActionInvocation;
  4: import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
  5: public class SimpleInterceptor extends AbstractInterceptor {
  6:   //简单的拦截器的名字
  7:   private String name;
  8:   //为该简单拦截器设置名字的setter方法
  9:   //拦截Action方法的intercept方法
 10:   @Override
 11:   public String intercept(ActionInvocation invocation) throws Exception {
 12:     // TODO Auto-generated method stub
 13:     //取得被拦截的Action实例
 14:     LoginAction action = (LoginAction) invocation.getAction();    
 15:     //打印
 16:     System.out.println("正在执行 ‘"+name+"’ 拦截器的动作========"+"开始执行登录的时间为："+new Date());    
 17:     //取得开始执行Action的时间
 18:     long start = System.currentTimeMillis();    
 19:     //执行该拦截器的后一个拦截器，或者直接指定Action的execute()方法
 20:     String result = invocation.invoke();
 21:     System.out.println("正在执行 ‘"+name+" ’拦截器的动作========"+"执行完登录的时间为："+new Date());  
 22:     //取得执行完Action的时间
 23:     long end = System.currentTimeMillis();
 24:     System.out.println("正在执行 ‘"+name+"’ 拦截器的动作========"+"Action执行了"+(end-start)+"毫秒");
 25:     return result;
 26:   }
 27:   public String getName() {
 28:     return name;
 29:   }
 30: 
 31:   public void setName(String name) {
 32:     this.name = name;
 33:   }
 34: }
 35:

2、struts.xml

  1: <?xml version="1.0" encoding="UTF-8" ?>
  2: <!DOCTYPE struts PUBLIC
  3:   "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
  4:   "http://struts.apache.org/dtds/struts-2.3.dtd">
  5: <struts>   
  6:   <package name="struts2" extends="struts-default">    
  7:     <!-- 配置应用所使用的拦截器 -->    
  8:         <interceptors>
  9:           <!-- 配置mysimple拦截器 -->
 10:           <interceptor name="mysimple" class="cc.openhome.SimpleInterceptor">
 11:             <!-- 为该拦截器指定参数值 -->
 12:             <param name="name">简单拦截器</param>
 13:           </interceptor>    
 14:           <interceptor name="authority" class="cc.openhome.AuthorityInterceptor"/>
 15:         </interceptors>  
 16:         <action name="login" class="cc.openhome.LoginAction">          
 17:           <result name="success">/success.jsp</result>
 18:           <result name="error">/error.jsp</result>
 19:           <result name="input">/denglu.jsp</result>
 20:           <interceptor-ref name="defaultStack"/>
 21:           <interceptor-ref name="mySimple">
 22:               <param name="name">动态拦截器</param>
 23:           </interceptor-ref>
 24:         </action>
 25:     </package>
 26: </struts>

3、登录页面login.jsp

  1: <%@ page language="java" contentType="text/html; charset=UTF-8"
  2:     pageEncoding="UTF-8"%>
  3: <%@ taglib prefix="s" uri="/struts-tags"%>
  4: <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
  5: <html>
  6:   <head>
  7:     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  8:     <title>登录界面</title>
  9:   </head>
 10:   <body>
 11:     <s:form action="login">
 12:       <s:textfield name="username" label="用户名"/>
 13:       <s:textfield name="password" label="密    码"/>
 14:       <s:submit value="登录"/>
 15:     </s:form>
 16:   </body>
 17: </html>

4、LoginAction.java

  1: package cc.openhome;
  2: import com.opensymphony.xwork2.Action;
  3: import com.opensymphony.xwork2.ModelDriven;
  4: public class LoginAction  implements Action{
  5:   private String username;
  6:   private String password;
  7:   public String getUsername() {
  8:     return username;
  9:   }
 10:   public void setUsername(String username) {
 11:     this.username = username;
 12:   }
 13:   public String getPassword() {
 14:     return password;
 15:   }
 16:   public void setPassword(String password) {
 17:     this.password = password;
 18:   }
 19:   @Override
 20:   public String execute() throws Exception {
 21:     // TODO Auto-generated method stub
 22:     return SUCCESS;
 23:   }
 24: }
 25:

5、运行结果

2、拦截器的执行顺序

修改struts.xml如下

  1: <?xml version="1.0" encoding="UTF-8" ?>
  2: <!DOCTYPE struts PUBLIC
  3:   "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
  4:   "http://struts.apache.org/dtds/struts-2.3.dtd">
  5: <struts> 
  6:   <constant name="struts.custom.i18n.resources" value="messageResource"></constant>
  7:   <package name="openhome" extends="struts-default">
  8:     <!-- 配置应用所使用的拦截器 -->    
  9:         <interceptors>
 10:           <!-- 配置mysimple拦截器 -->
 11:           <interceptor name="mysimple" class="cc.openhome.SimpleInterceptor">
 12:             <!-- 为该拦截器指定参数值 -->
 13:             <param name="name">简单拦截器</param>
 14:           </interceptor>
 15:         </interceptors>      
 16:     <action name="login" class="cc.openhome.LoginAction" method="execute">
 17:       <result name="input">/input.jsp</result>
 18:       <result name="success">/WEB-INF/page/welcome.jsp</result>
 19:       <result name="error">/WEB-INF/page/error.jsp</result>
 20:       <interceptor-ref name="defaultStack" />
 21:       <interceptor-ref name="mysimple">
 22:         <param name="name">第一个动态拦截器</param>
 23:       </interceptor-ref>
 24:       <interceptor-ref name="mysimple">
 25:         <param name="name">第二个动态拦截器</param>
 26:       </interceptor-ref>      
 27:     </action>
 28:   </package>
 29:     <!-- Add packages here -->
 30: </struts>
 31:

运行结果如下：可以看到先配置的拦截器，先获得执行机会。

3、方法拦截器

如果不需要拦截特定的方法，假如不拦截execute方法，则在控制台上就不会输出任何信息。

只需要修改提供方法过滤的拦截器

MyFilterInterceptor.java

  1: package cc.openhome;
  2: import java.util.Date;
  3: import com.opensymphony.xwork2.ActionInvocation;
  4: import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;
  5: public class MyFilterInterceptor extends MethodFilterInterceptor {
  6:   private String name;  
  7:   public String getName() {
  8:     return name;
  9:   }
 10:   public void setName(String name) {
 11:     this.name = name;
 12:   }
 13:   @Override
 14:   protected String doIntercept(ActionInvocation invocation) throws Exception {
 15:     // TODO Auto-generated method stub
 16:     //取得被拦截的Action实例
 17:         LoginAction action = (LoginAction) invocation.getAction();
 18:         
 19:         //打印
 20:         System.out.println("正在执行 ‘"+name+"’ 拦截器的动作========"+"开始执行登录的时间为："+new Date());
 21:         
 22:         //取得开始执行Action的时间
 23:         long start = System.currentTimeMillis();
 24:         
 25:         //执行该拦截器的后一个拦截器，或者直接指定Action的execute()方法
 26:         String result = invocation.invoke();
 27:         System.out.println("正在执行 ‘"+name+" ’拦截器的动作========"+"执行完登录的时间为："+new Date());
 28:         
 29:         //取得执行完Action的时间
 30:         long end = System.currentTimeMillis();
 31:         System.out.println("正在执行 ‘"+name+"’ 拦截器的动作========"+"Action执行了"+(end-start)+"毫秒");
 32:         return result;
 33:   }
 34: }
 35:

struts.xml

  1: <?xml version="1.0" encoding="UTF-8" ?>
  2: <!DOCTYPE struts PUBLIC
  3:   "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
  4:   "http://struts.apache.org/dtds/struts-2.3.dtd">
  5: <struts> 
  6:   <package name="openhome" extends="struts-default">
  7:     <!-- 配置应用所使用的拦截器 -->    
  8:         <interceptors>
  9:           <!-- 配置myfilter拦截器 -->
 10:           <interceptor name="myfilter" class="cc.openhome.MyFilterInterceptor">
 11:             <!-- 为该拦截器指定参数值 -->
 12:             <param name="name">方法过滤拦截器</param>
 13:           </interceptor>  
 14:           </interceptor>        
 15:           <interceptor name="authority" class="cc.openhome.AuthorityInterceptor"/>
 16:         </interceptors>      
 17:     <action name="login" class="cc.openhome.LoginAction" method="execute">
 18:       <result name="input">/input.jsp</result>
 19:       <result name="success">/WEB-INF/page/welcome.jsp</result>
 20:       <result name="error">/WEB-INF/page/error.jsp</result>
 21:       <interceptor-ref name="defaultStack" />
 22:       <interceptor-ref name="myfilter">
 23:         <param name="name">改名后的方法拦截器</param>
 24:         <param name="excludeMethods">execute</param>
 25:       </interceptor-ref>      
 26:     </action>
 27:   </package>  
 28:     <!-- Add packages here -->
 29: </struts>
 30:

3、拦截结果的监听器

为了更精确的定义在execute方法执行前后的结构，以及执行后再处理Result执行的动作。这个监听器通过手动注册在拦截内部，必须实现PreReslutListener接口。

MyPreResultListener.java

  1: package cc.openhome;
  2: import com.opensymphony.xwork2.ActionInvocation;
  3: import com.opensymphony.xwork2.interceptor.PreResultListener;
  4: public class MyPreResultListener implements PreResultListener {
  5:   @Override
  6:   public void beforeResult(ActionInvocation invocation, String resultCode) {
  7:     // TODO Auto-generated method stub
  8:     System.out.println("返回的逻辑视图是："+resultCode);
  9:   }
 10: }
 11:

BeforeResultInterceptor.java

  1: package cc.openhome;
  2: import com.opensymphony.xwork2.ActionInvocation;
  3: import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
  4: public class BeforeResultInterceptor extends AbstractInterceptor {  
  5:   @Override
  6:   public String intercept(ActionInvocation invocation) throws Exception {
  7:     // TODO Auto-generated method stub
  8:     //将一个拦截器结果的监听器注册给该拦截器
  9:     invocation.addPreResultListener(new MyPreResultListener());
 10:     System.out.println("execute方法执行之前的拦截。。。");    
 11:     //调用下一个拦截器，或者Action的执行方法execute()
 12:     String result = invocation.invoke();
 13:     System.out.println("execute方法执行之后的拦截。。。");
 14:     return result;
 15:   }  
 16: }
 17: