springboot三种过滤功能的使用与比较

若要实现对请求的过滤，有三种方式可供选择：filter、interceptort和aop。本文主要讨论三种拦截器的使用场景与使用方式。

下文中的举例功能是计算每个请求的从开始到结束的时间，例子来源是慕课网。

一、filter

特点：可以获取原始的ServletRequest，但无法获取具体方法

实现：

1.继承javax.servlet.Filter类，

2.@Component注解将其注入到框架中

3.实现其中的dofilter方法，所有的请求都会经过该方法，可以在此计算出每个请求的耗时，代码如下：

package com.zzy.web.filter;

import java.io.IOException;
import java.util.Date;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.stereotype.Component;

@Component
public class TimeFilter implements Filter{

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("filter init");
        
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
        Long startTime = new Date().getTime();
        System.out.println("filter 请求开始时间:"+ startTime);
        chain.doFilter(request, response);
         Long endTime = new Date().getTime();
        System.out.println("filter 请求结束时间：" + endTime +",请求耗时：" + (endTime - startTime));
        
    }

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
        
    }

}

注：如果有的框架没有@Component 这个注解，可以自己写一个配置类，在该类中指定过滤器，而且还可以指定过滤的url，配置类如下：

package com.zzy.web.config;

import static org.assertj.core.api.Assertions.failBecauseExceptionWasNotThrown;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import com.zzy.web.filter.TimeFilter;
import com.zzy.web.interceptor.TimeInterceptor;

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    
    @Autowired
    private TimeInterceptor timeInterceptor;
    
//    @Override
//    public void addInterceptors(InterceptorRegistry registry) {
//        // TODO Auto-generated method stub
//        registry.addInterceptor(timeInterceptor);
//    }
    
    @Bean
    public FilterRegistrationBean timeFilter() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        TimeFilter timeFilter = new TimeFilter();
        registrationBean.setFilter(timeFilter);
        List<String> urls = new ArrayList<>();
        urls.add("/user/*");
        registrationBean.setUrlPatterns(urls);
        return registrationBean;
    }

}

二、interceptor

特点：可以获取到原始的request和请求的方法，但无法获取方法的具体参数的值。

实现：

1.继承HandlerInterceptor接口

2.请求前的逻辑写在prehandle（请求前调用）

3.请求后的逻辑写在posthandle（请求成功后调用，失败则不调用）

4.请求后，不管成功失败都会调用aftercompletion。

5.intceptor方式继承了之后还没起作用，还需要在配置类里面加一下，把刚声明的拦截器注册一下。

代码示例：

package com.zzy.web.interceptor;

import java.util.Arrays;
import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
@Component
public class TimeInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        // TODO Auto-generated method stub
        System.out.println("interceptor 执行preHandle");

        request.setAttribute("startTime", new Date().getTime());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        // TODO Auto-generated method stub
        Long startTime = Long.parseLong(request.getAttribute("startTime").toString());
        Long endTime = new Date().getTime();
        System.out.println("interceptor 执行postHandle");
        System.out.println("interceptor 请求类："+((HandlerMethod)handler).getBean().getClass().getName());
        System.out.println("interceptor 请求方法："+((HandlerMethod)handler).getMethod());
//        System.out.println("interceptor 请求参数：");
//        Arrays.asList(((HandlerMethod)handler).getMethodParameters()).stream().forEach(arg->System.out.println(arg));
        System.out.println("interceptor 请求耗时：" + (endTime - startTime));

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        // TODO Auto-generated method stub
        Long startTime = Long.parseLong(request.getAttribute("startTime").toString());
        Long endTime = new Date().getTime();
        System.out.println("interceptor 执行afterCompletion");
        System.out.println("interceptor 请求类："+((HandlerMethod)handler).getBean().getClass().getName());
        System.out.println("interceptor 请求方法："+((HandlerMethod)handler).getMethod());
        System.out.println("interceptor 请求耗时：" + (endTime - startTime));
        System.out.println("interceptor 请求异常：" + ex);

    }

}

配置类如下：

package com.zzy.web.config;

import static org.assertj.core.api.Assertions.failBecauseExceptionWasNotThrown;

import java.util.ArrayList;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import com.zzy.web.filter.TimeFilter;
import com.zzy.web.interceptor.TimeInterceptor;

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    
    @Autowired
    private TimeInterceptor timeInterceptor;
    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // TODO Auto-generated method stub
        registry.addInterceptor(timeInterceptor);
    }


}

三、aop

特点：能拿到方法和具体参数的值，但是拿不到原始的servletrequest的信息。

实现：

1.使用@aspect注解

2.@execution声明切面，声明切面的语法可参考官网https://docs.spring.io/spring/docs/4.3.18.RELEASE/spring-framework-reference/htmlsingle/#aop-pointcuts

3.使用@Around(方法前和方法后),@Before（方法前）或@After（方法后）

以下为@Around举例，代码如下：

package com.zzy.web.aspect;

import java.util.Date;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.codehaus.jackson.map.ObjectMapper;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class TimeAspect {

    @Around("execution(* com.zzy.web.controller.UserController.*(..))")
    public Object test(ProceedingJoinPoint pjp) throws Throwable {
        Long startTime = new Date().getTime();
        Object[] args = pjp.getArgs();
        for (Object arg : args) {
            System.out.println("aspect 参数：" + arg);
        }
        Object object = pjp.proceed();
        System.out.println("aspect 请求耗时：" + (new Date().getTime() - startTime));
        System.out.println("aspect 请求结果：" + new ObjectMapper().writeValueAsString(object));

        return object;

    }
}

 下图是三种方式的拦截顺序，图片来自慕课网：