SpringMVC中的拦截器

public class MyInterceptor implements HandlerInterceptor {
    
    /**
     * 预处理 controller方法执行前执行
     * return true 放行 ,执行下一个拦截器, 如果没有, 执行controller中的方法
     * return false  不放行, 可以直接跳转到其他页面
     * @param request
     * @param response
     * @param handler
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle (HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println ("preHandle....");
        HttpSession session = request.getSession ();
        //如果用户名已存在,直接跳转到个人中心页面
        if (null!=session.getAttribute ("username")){
            request.getRequestDispatcher("/WEB-INF/pages/PersonalCenter.jsp").forward(request, response);
            return false;
        }
        //用户名不存在,用户未登陆, 可以进入登录页面,进行登录
        return true;
    }

    /**
     * 后处理方法, controller方法执行后, 跳转到对应页面之前
     * @param request
     * @param response
     * @param handler
     * @param modelAndView
     * @throws Exception
     */
    @Override
    public void postHandle (HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println ("postHandle...");
    }

    @Override
    public void afterCompletion (HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println ("afterCompletion..");
    }
}

@Controller
@RequestMapping("/UserControl")
public class UserController {

    //跳转到登录页面
    @RequestMapping("/GoLogin")
    public String GoLogin() throws Exception{
        System.out.println ("now begin jump Login page");
        return "Login";
    }

    @RequestMapping("/Login")
    //登录操作
    public String Login(User user,HttpSession session){
        System.out.println (user);
        //如果登录成功, 把用户名存进session域对象中
        session.setAttribute ("username",user.getUsername ());
        //跳转到个人中心
        System.out.println ("now begin jump PersonalCenter page");
        return "PersonalCenter";
    }

    @RequestMapping("/Logout")
    public String Logout(HttpSession session) throws Exception{
        System.out.println ("Logout....");
        //session过期
        session.invalidate ();
        System.out.println ("now begin jump index page");
        return "redirect:../index.jsp";
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 开启注解扫描 -->
    <context:component-scan base-package="com.mkl"/>

    <!-- 视图解析器对象 -->
    <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!--前端控制器，哪些静态资源不拦截-->
    <!-- 不处理静态内容 -->
    <mvc:default-servlet-handler/>
    <mvc:resources location="/css/" mapping="/css/**"/>
    <mvc:resources location="/images/" mapping="/images/**"/>
    <mvc:resources location="/js/" mapping="/js/**"/>

    <!-- 开启SpringMVC框架注解的支持 -->
    <mvc:annotation-driven />

    <!--配置拦截器-->
    <!--配置拦截器-->
    <mvc:interceptors>
        <!--配置拦截器-->
        <mvc:interceptor>
            <!--要拦截的具体的方法-->
            <mvc:mapping path="/UserControl/GoLogin"/>
            <mvc:mapping path="/UserControl/Login"/>
            <!--不要拦截的方法-->
            <!--<mvc:exclude-mapping path=""/>-->
            <!--配置拦截器对象-->
            <bean class="com.mkl.interceptor.MyInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

</beans>

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>

  <!--配置解决中文乱码的过滤器-->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>


  <!--配置前端控制器-->
  <servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcherServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

</web-app>