spring裡的三大攔截器

摘要： Filter 新建 TimeFilter @Component public class TimeFilter implements Filter { @Override public void init(FilterConfig filterConfig) throw...

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");
}
}

啟動伺服器，在瀏覽器輸入：http://localhost:8080/hello?name=tom

可以在控制檯輸出如下結果：

time filter start

name: tom

time filter consume 3 ms

time filter end

可以看到，filter 先執行，再到真正執行 HelloController.sayHello() 方法。

通過 TimeFilter.doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) 方法的引數可以看出，我們只能得到原始的 request 和 response 物件，不能得到這個請求被哪個 Controller 以及哪個方法處理了，使用Interceptor 就可以獲得這些資訊。

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;
// 獲取處理當前請求的 handler 資訊
System.out.println("handler 類：" + handlerMethod.getBeanType().getName());
System.out.println("handler 方法：" + handlerMethod.getMethod().getName());

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

// 把當前時間放入 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");
}
}

註冊 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);
}
}

啟動伺服器，在瀏覽器輸入：http://localhost:8080/hello?name=tom

可以在控制檯輸出如下結果：

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 先於 interceptor 執行，再到真正執行 HelloController.sayHello() 方法。通過 interceptor 方法上的 handler 引數，我們就可以得到這個請求被哪個Controller 以及哪個方法處理了 。但是不能直接獲取到這個方法上的引數值（在這裡就是 HelloController.sayHello(String name) 方法引數 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;
}

}

啟動伺服器，在瀏覽器輸入：http://localhost:8080/hello?name=tom

可以在控制檯輸出如下結果：

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 先執行，再到 interceptor 執行，再到 aspect 執行，再到真正執行 HelloController.sayHello() 方法。

我們也獲取到了 HelloController.sayHello(String name) 方法引數 name 的值 。

請求攔截過程圖

graph TD
httprequest-->filter
filter-->interceptor
interceptor-->aspect
aspect-->controller