Filter、Interceptor、AOP三种拦截方式比较

Filter

javax.servlet.filter 是java sevlet规范定义的接口,定义了3个方法

public void init(FilterConfig filterConfig) throws ServletException;

public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException;

public void destroy();

filter 的缺点在于无法拿到具体请求的哪个controller的哪个方法

Interceptor

通过org.springframework.web.servlet.HandlerInterceptor接口实现

该接口是由SpringMVC提供，有三个方法

default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    return true;
}

default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
}

default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
}

该方式可以拿到请求的具体类名和方法

((HandlerMethod)handler).getBean().getClass().getName()
((HandlerMethod)handler).getMethod().getName()

但是这种方式拿不到方法上的具体参数值

AOP

可以通过ProceedingJoinPoint 拿到具体的参数值
但是无法获取HttpServletRequest 和HttpServletResponse 对象

@Around("execution(* com.jerio.web.controller.UserController.*(..))")
public Object handleControllerMethod(ProceedingJoinPoint pjp) throws Throwable {
    Object[] args = pjp.getArgs();
        for (Object arg : args) {
            System.out.println("arg is "+arg);
        }
// 获取类名
pjp.getSignature().getDeclaringTypeName()
// 获取方法名
pjp.getSignature().getName()
}

如果想要拿到Request对象，需要借助Spring提供的org.springframework.web.context.request.RequestContextHolder，该类使用ThreadLocal保存了本次请求的相关信息

ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = attributes.getRequest();