SpringBoot-拦截器

1.概述

对访问路径进行拦截和放行的，底层使用的是java反射机制（动态代理）

2.创建拦截器

1. 创建拦截类

   import org.springframework.web.servlet.HandlerInterceptor;
   import org.springframework.web.servlet.ModelAndView;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.util.Date;
   
   /*
   实现HandlerInterceptor接口
   重写方法
   */
   @Component
   public class LoginInterceptor implements HandlerInterceptor {
       /*
       该方法，处于controller之前执行，进行对请求地址的拦截
       true为放行，false为拦截
       */
       @Override
       public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
           System.out.println(new Date() + "preHandle:" + request.getRequestURL());
           //判断名为user的session是否为null
           //是则false
           //否是true
           return request.getSession().getAttribute("user") != null;
       }
   	/*
   	处于controller完毕后，做的一些改动，比如返回前端值为5，可以在这里更改为6
   	*/
       @Override
       public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
           System.out.println(new Date() + "postHandle:" + request.getRequestURL());
       }
   	/*
   	释放内存，清理内存变量
   	*/
       @Override
       public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
           System.out.println(new Date() + "afterCompletion:" + request.getRequestURL());
       }
   }
   

2. 创建配置类

   import com.dragon.interceptor.LoginInterceptor;
   import lombok.extern.slf4j.Slf4j;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
   import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
   import javax.annotation.Resource;
   
   @Slf4j
   @Configuration
   public class MyWebMvcConfig implements WebMvcConfigurer {
       @Resource
       private LoginInterceptor loginInterceptor;
   
       @Override
       public void addInterceptors(InterceptorRegistry registry) {
           registry.addInterceptor(loginInterceptor)
                   .addPathPatterns("/**") //拦截所有路径
                   .excludePathPatterns("/user/login");//放行指定路径
       }
   }
   
   

   当用户未登录时，Interceptor中的preHandler()返回false，进行拦截所有路径（除了"/user/login"）

   当用户登录成功后，Interceptor中的preHandler()返回true，进行所有路径放行