Filter

新建 TimeFilter

@Component
public class TimeFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("time filter init");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("time filter start");
        long startTime = System.currentTimeMillis();

        filterChain.doFilter(servletRequest, servletResponse);

        long endTime = System.currentTimeMillis();
        System.out.println("time filter consume " + (endTime - startTime) + " ms");
        System.out.println("time filter end");
    }

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

啟動(dòng)服務(wù)器，在瀏覽器輸入：http://localhost:8080/hello?name=tom
可以在控制臺輸出如下結(jié)果：

time filter start
name: tom
time filter consume 3 ms
time filter end

可以看到，filter 先執(zhí)行，再到真正執(zhí)行 HelloController.sayHello() 方法。
通過 TimeFilter.doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) 方法的參數(shù)可以看出，我們只能得到原始的 request 和 response對象，不能得到這個(gè)請求被哪個(gè) Controller 以及哪個(gè)方法處理了，使用Interceptor 就可以獲得這些信息。

Interceptor

新建 TimeInterceptor

@Component
public class TimeInterceptor extends HandlerInterceptorAdapter {

    private final NamedThreadLocal<Long> startTimeThreadLocal = new NamedThreadLocal<>("startTimeThreadLocal");

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("time interceptor preHandle");

        HandlerMethod handlerMethod = (HandlerMethod) handler;
        // 獲取處理當(dāng)前請求的 handler 信息
        System.out.println("handler 類：" + handlerMethod.getBeanType().getName());
        // 方法名，方法注解，注解的值都可以獲取
        System.out.println("handler 方法：" + handlerMethod.getMethod().getName());

        MethodParameter[] methodParameters = handlerMethod.getMethodParameters();
        for (MethodParameter methodParameter : methodParameters) {
            String parameterName = methodParameter.getParameterName();
            // 只能獲取參數(shù)的名稱，不能獲取到參數(shù)的值
            //System.out.println("parameterName: " + parameterName);
        }

        // 把當(dāng)前時(shí)間放入 threadLocal
        startTimeThreadLocal.set(System.currentTimeMillis());

        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("time interceptor postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

        // 從 threadLocal 取出剛才存入的 startTime
        Long startTime = startTimeThreadLocal.get();
        long endTime = System.currentTimeMillis();

        System.out.println("time interceptor consume " + (endTime - startTime) + " ms");

        System.out.println("time interceptor afterCompletion");
    }
}

注冊 TimeInterceptor
把 TimeInterceptor 注入 spring 容器

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {

    @Autowired
    private TimeInterceptor timeInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(timeInterceptor);
    }
}

啟動(dòng)服務(wù)器，在瀏覽器輸入：http://localhost:8080/hello?name=tom
可以在控制臺輸出如下結(jié)果：

time filter start
time interceptor preHandle
handler 類：com.nextyu.demo.web.controller.HelloController
handler 方法：sayHello
name: tom
time interceptor postHandle
time interceptor consume 40 ms
time interceptor afterCompletion
time filter consume 51 ms
time filter end

可以看到，filter 先于 interceptor 執(zhí)行，再到真正執(zhí)行 HelloController.sayHello() 方法。通過 interceptor 方法上的 handler 參數(shù)，我們就可以得到這個(gè)請求被哪個(gè) Controller 以及哪個(gè)方法處理了。但是不能直接獲取到這個(gè)方法上的參數(shù)值（在這里就是 HelloController.sayHello(String name) 方法參數(shù) name 的值），通過 Aspect 就可以獲取到。

Aspcet

新建 TimeAspect

@Aspect
@Component
public class TimeAspect {

    @Around("execution(* com.nextyu.demo.web.controller.*.*(..))")
    public Object handleControllerMethod(ProceedingJoinPoint pjp) throws Throwable {

        System.out.println("time aspect start");

        Object[] args = pjp.getArgs();
        for (Object arg : args) {
            System.out.println("arg is " + arg);
        }

        long startTime = System.currentTimeMillis();

        Object object = pjp.proceed();

        long endTime = System.currentTimeMillis();
        System.out.println("time aspect consume " + (endTime - startTime) + " ms");

        System.out.println("time aspect end");

        return object;
    }

}

啟動(dòng)服務(wù)器，在瀏覽器輸入：http://localhost:8080/hello?name=tom
可以在控制臺輸出如下結(jié)果：

time filter start
time interceptor preHandle
handler 類：com.nextyu.demo.web.controller.HelloController
handler 方法：sayHello
time aspect start
arg is tom
name: tom
time aspect consume 0 ms
time aspect end
time interceptor postHandle
time interceptor consume 2 ms
time interceptor afterCompletion
time filter consume 4 ms
time filter end

可以看到，filter 先執(zhí)行，再到 interceptor 執(zhí)行，再到 aspect 執(zhí)行，再到真正執(zhí)行 HelloController.sayHello() 方法。
我們也獲取到了 HelloController.sayHello(String name) 方法參數(shù) name 的值。

請求攔截過程圖

• Filter 可獲取原始http請求上下文
• Interceptor 可獲取類和方法及方法注解元信息
• Aspect 可獲取方法參數(shù)具體信息