简介

拦截器是基于web框架的调用，因此可以使用Spring的依赖注入（DI）进行一些业务操作。在SpringMVC中就是依赖于SpringMVC框架。在实现上基于Java的反射机制，属于面向切面编程（AOP）的一种运用。

主要工作场景

拦截器可以获取IOC容器中的各个bean，而过滤器就不行，所以在拦截器里注入一个service，可以调用业务逻辑。
拦截器只能对controller请求进行拦截，对其他的一些比如直接访问静态资源的请求则没办法进行拦截处理。

实现

1. 定义自己拦截器

/**
 * Created by liusj 2019/6/29
 */
@Log
public class MyInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("MyInterceptor == preHandler ");
        long startTime = System.nanoTime();
        request.setAttribute("startTime", startTime);
        return super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("MyInterceptor == postHandle ");
        super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("MyInterceptor == afterCompletion ");

        Long startTime = (Long) request.getAttribute("startTime");
        long endTime = System.nanoTime();
        // 打印出接口请求时间
        log.info("This method expired :" + (endTime - startTime) / 1000000 + " 毫秒");

        super.afterCompletion(request, response, handler, ex);
    }
}

2. 配置(添加到Spring中)

@Configuration
public class MyMvcConfigure extends WebMvcConfigurerAdapter {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/");// 添加拦截路径
        super.addInterceptors(registry);
    }
}

由于SpringBoot2中WebMvcConfigurerAdapter过时@Deprecated，这里通过实现WebMvcConfigurer来实现拦截器的配置。

/**
 * Created by liusj 2019/6/29
 */
@Configuration
public class MyMvcConfigure2 implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/");// 添加拦截路径
    }
}

测试

@SpringBootApplication
@RestController
@Log
public class Application {

    @RequestMapping(value = "/")
    public String home() {
        log.info("接口请求");
        return "Hello Interceptor World";
    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}