Springboot 三种拦截Rest API的方法-过滤器、拦截器、切片

过滤器方式实现拦截（Filter）

通过继承Servlet的Filter类来实现拦截：

@Component
public class TimeFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("time filter init");
    }
    /**
     * 处理服务的请求时间
     * @param request
     * @param response
     * @param chain
     * @throws IOException
     * @throws ServletException
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        //System.out.println("time filter start");
        long start = System.currentTimeMillis();
        chain.doFilter(request,response);
        //System.out.println("time filter 耗时:" + (System.currentTimeMillis() - start));
        //System.out.println("time filter finish");

    }
    @Override
    public void destroy() {
        //System.out.println("time filter destroy");
    }
}

假如这个Filter是第三方jar提供的，怎么加入我们自己的工程呢？通过org.springframework.boot.web.servlet.FilterRegistrationBean来加入

@Configuration
public class WebConfig {
    
    @Bean
    public FilterRegistrationBean timeFilter() {
        
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        
        TimeFilter timeFilter = new TimeFilter();
        registrationBean.setFilter(timeFilter);
        
        List<String> urls = new ArrayList<>();
        urls.add("/*");
        registrationBean.setUrlPatterns(urls);
        
        return registrationBean;
        
    }

}

拦截器方式实现拦截（Interceptor）

此种方式可以获取到拦截的类名称、方法名称，不能获取到方法参数，原因是在dispatcherservlet源码中，经过preHandle才对方法参数通过request里面开始处理拼接）

1.继承HandlerInterceptor，preHandle在控制器方法调用之前执行，postHandle在控制器方法正常执行后执行，afterCompletion不管控制器方法执行成功与否，都会执行;拦截器优于过滤器的地方就是拦截器有handler这个参数可以了解到针对哪个具体的方法进行了拦截。

@Component
public class TimeInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle");
        //打印类名
        System.out.println(((HandlerMethod)handler).getBean().getClass().getName());
        //打印方法名
        System.out.println(((HandlerMethod)handler).getMethod().getName());
        request.setAttribute("startTime",System.currentTimeMillis());
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle");
        Long start = (Long)request.getAttribute("startTime");
        System.out.println("time intercept 耗时：" + (System.currentTimeMillis() - start));
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object o, Exception ex) throws Exception {
        System.out.println("afterCompletion");
        Long start = (Long)request.getAttribute("startTime");
        System.out.println("time intercept 耗时：" + (System.currentTimeMillis() - start));
        System.out.println("ex is" + ex);
    }
}

2. 配置拦截器注入到spring容器（配置类需要继承WebMvcConfigurerAdapter，重写addInterceptors，手动添加自定义拦截器来到达注入的目的），也可为异步请求加入拦截器

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Autowired
    private TimeInterceptor timeInterceptor;

    /**
     * 针对异步的拦截器配置，拦截异步请求
     * @param configurer
     */
    @Override
    public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
        super.configureAsyncSupport(configurer);
        //比如如下给异步服务请求添加拦截器
        //configurer.registerCallableInterceptors((CallableProcessingInterceptor) timeInterceptor);
    }
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(timeInterceptor);
    }
}

切片方式实现拦截（Aspect）

可以拦截到类名、方法名，方法参数名

@Aspect
@Component
public class TimeAspect {
    //切入点
    @Around("execution(* com.zlt.web.controller.UserController.*(..))")
    //增强
    public Object handleControllerMethod(ProceedingJoinPoint pjp) throws Throwable {

            System.out.print("time aspect start");
            Object[] args = pjp.getArgs();
            for (Object arg :args){
            System.out.println("arg is" + arg);
            }
            long start = System.currentTimeMillis();
            //调用被拦截的方法
            Object object = pjp.proceed();
            System.out.println("time filter 耗时：" + (System.currentTimeMillis() - start));
            System.out.println("time aspect end");
            return object; 
    }
}

小结

区别：

过滤器：可以拿到原始的HTTP请求和响应信息，拿不到处理请求的方法值信息 
拦截器：既可以拿到HTTP请求和响应信息，也可以拿到请求的方法信息，拿不到方法调用的参数值信息 
切片：可以拿到请求方法的传入参数值，拿不到原始的HTTP请求和响应的对象

发起一个请求，若三者共存的情况下：

正常运行顺序为：filter-interceptor-controllerAdvice-aspect-controller
异常情况下：controller-aspect-controllerAdvice-interceptor-filter