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:

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:   <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myresult拦截器 -->

 11:           <interceptor name="myresult" class="cc.openhome.BeforeResultInterceptor">

 12:             <!-- 为该拦截器指定参数值 -->

 13:             <param name="name">结果的拦截器</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="myresult">

 22:         <param name="name">结果拦截器</param>

 23:       </interceptor-ref>

 24:     </action>

 25:     <!-- Add packages here -->

 26: </struts>

 27:

运行结果