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"); } }
启动服务器,在浏览器输入:http://localhost:8080/hello?name=tom
可以在控制台输出如下结果:

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

可以看到,filter 先执行,再到真正执行 HelloController.sayHello() 方法。
通过 TimeFilter.doFilter(ServletRequest servletRequest, ServletResponse
servletResponse, FilterChain filterChain) 方法的参数可以看出,我们只能得到原始的 request 和 response
对象,不能得到这个请求被哪个 Controller 以及哪个方法处理了,使用Interceptor 就可以获得这些信息。

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; // 获取处理当前请求的 handler 信息
System.out.println("handler 类:" + handlerMethod.getBeanType().getName());
System.out.println("handler 方法:" + handlerMethod.getMethod().getName());
MethodParameter[] methodParameters = handlerMethod.getMethodParameters(); for
(MethodParameter methodParameter : methodParameters) { String parameterName =
methodParameter.getParameterName(); // 只能获取参数的名称,不能获取到参数的值
//System.out.println("parameterName: " + parameterName); } // 把当前时间放入
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 { // 从 threadLocal
取出刚才存入的 startTime Long startTime = startTimeThreadLocal.get(); long endTime =
System.currentTimeMillis(); System.out.println("time interceptor consume " +
(endTime - startTime) + " ms"); System.out.println("time interceptor
afterCompletion"); } }
注册 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); } }
启动服务器,在浏览器输入:http://localhost:8080/hello?name=tom
可以在控制台输出如下结果:
time filter start time interceptor preHandle handler
类: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 执行,再到真正执行 HelloController.sayHello() 方法。通过
interceptor 方法上的 handler 参数,我们就可以得到这个请求被哪个Controller 以及哪个方法处理了
。但是不能直接获取到这个方法上的参数值(在这里就是 HelloController.sayHello(String name) 方法参数 name
的值),通过 Aspect 就可以获取到。

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; } }
启动服务器,在浏览器输入:http://localhost:8080/hello?name=tom
可以在控制台输出如下结果:
time filter start time interceptor preHandle handler
类: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 先执行,再到 interceptor 执行,再到 aspect 执行,再到真正执行
HelloController.sayHello() 方法。
我们也获取到了 HelloController.sayHello(String name) 方法参数 name 的值。

请求拦截过程图
graph TD httprequest-->filter filter-->interceptor interceptor-->aspect
aspect-->controller