拦截器, 技术java反射技术, 不依赖Spring容器, 可以使用 Spring 容器管理的bean.

客户端发起请求到 DispatcherServlet , 然后根据 HandlerMapping 匹配处理器, 返回一个 HandlerExecution 对象, 包含 处理器 和 拦截器, 这里的拦截器会对处理器进行拦截, 通过拦截器可以增强处理器的功能.

1. 创建拦截器, 实现 HandlerInterceptor 接口

package com.codingos.springboot.test.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;public class Interceptor1 implements HandlerInterceptor {	/**	 * 在 controller 方法之前执行, 返回false则结束, 返回true则继续下一步.	 */	@Override	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {		System.out.println("****** 处理器前方法 *******");		return true;//		request.getRequestDispatcher("/file/uploadPage").forward(request, response);//		return false;	}	/**	 * 在处理器方法之后, 视图渲染之前执行.	 */	@Override	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {		System.out.println("****** 处理器后方法 *******");		HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);	}	/**	 * 在视图渲染之后执行	 */	@Override	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {		System.out.println("****** 处理器完成后方法 *******");		HandlerInterceptor.super.afterCompletion(request, response, handler, ex);	}}

package com.codingos.springboot.test.interceptor;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor;import org.springframework.web.servlet.ModelAndView;public class MultiInterceptor1 implements HandlerInterceptor {	@Override	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {		System.out.println(this.getClass().getName() + "处理器前方法");		return true;	}		@Override	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {		System.out.println(this.getClass().getName() + "处理器后方法");		HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);	}		@Override	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {		System.out.println(this.getClass().getName() + "处理器完成后方法");		HandlerInterceptor.super.afterCompletion(request, response, handler, ex);	}}

2. 注册拦截器, springboot 主类 实现 WebMvcConfigurer

@SpringBootApplicationpublic class SpringBootTestApplication implements WebMvcConfigurer{		/**	 * 注册拦截器	 */	@Override	public void addInterceptors(InterceptorRegistry registry) {//		registry.addInterceptor(new Interceptor1()).addPathPatterns("/interceptor/*");		registry.addInterceptor(new MultiInterceptor1()).addPathPatterns("/interceptor/*");		registry.addInterceptor(new MultiInterceptor2()).addPathPatterns("/interceptor/*");		registry.addInterceptor(new MultiInterceptor3()).addPathPatterns("/interceptor/*");	}	public static void main(String[] args) {		SpringApplication.run(SpringBootTestApplication.class, args);	}}

3. 多个拦截器的顺序

com.codingos.springboot.test.interceptor.MultiInterceptor1处理器前方法com.codingos.springboot.test.interceptor.MultiInterceptor2处理器前方法com.codingos.springboot.test.interceptor.MultiInterceptor3处理器前方法执行处理器逻辑com.codingos.springboot.test.interceptor.MultiInterceptor3处理器后方法com.codingos.springboot.test.interceptor.MultiInterceptor2处理器后方法com.codingos.springboot.test.interceptor.MultiInterceptor1处理器后方法视图渲染com.codingos.springboot.test.interceptor.MultiInterceptor3处理器完成后方法com.codingos.springboot.test.interceptor.MultiInterceptor2处理器完成后方法com.codingos.springboot.test.interceptor.MultiInterceptor1处理器完成后方法