Java 中的过滤器Filter 和拦截器 Interceptor

1.先说拦截器 Interceptor

本项目以springboot为例：

新建

InterceptorConfig

package com.opendev.mystudy.MyInterceptor;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class InterceptorConfig extends WebMvcConfigurerAdapter {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
}

MyInterceptor

package com.opendev.mystudy.MyInterceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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

public class MyInterceptor implements HandlerInterceptor{
    /**
     *
     * preHandle是请求执行前执行的，postHandler是请求结束执行的，
     * 但只有preHandle方法返回true的时候才会执行，afterCompletion是视图渲染完成后才执行，
     * 同样需要preHandle返回true，该方法通常用于清理资源等工作。
     *
     */
    long start = System.currentTimeMillis();

    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("preHandle。。。");
        start = System.currentTimeMillis();
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle。。。");
        System.out.println("Interceptor cost="+(System.currentTimeMillis()-start));
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("afterCompletion。。。");
    }
}

执行的顺序如下

　　

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2.再说说 Filter ，先集成到配置类中

FiterConfig

package com.opendev.mystudy.MyFilter;

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FilterConfig {

    @Bean
    public FilterRegistrationBean registFilter() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new MyFilter());
        registration.addUrlPatterns("/test/frist/*");
        registration.setName("MyFilter");
        registration.setOrder(1);
        return registration;
    }
}

MyFilter

package com.opendev.mystudy.MyFilter;

import javax.servlet.*;
import javax.servlet.FilterConfig;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

/**
 * 用这个@WebFilter就要在主类上配置@ServletComponentScan
 */
//@ServletComponentScan("com.opendev.mystudy.MyFilter")
@WebFilter(urlPatterns = "/*", filterName = "MyFilter")
public class MyFilter implements Filter {

    /**
     *
     * servlet 初始化过程
     * @param filterConfig
     * @throws ServletException
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("进入了 init 方法");
    }

    /**
     *
     * 这段代码的逻辑比较简单，就是在方法执行前先记录时间戳，
     * 然后通过过滤器链完成请求的执行，在返回结果之间计算执行的时间。
     * 这里需要主要，这个类必须继承Filter类，这个是Servlet的规范，
     * 这个跟以前的Web项目没区别。但是，有了过滤器类以后，
     * 以前的web项目可以在web.xml中进行配置，但是spring boot项目并没有web.xml这个文件，
     *
     * @param servletRequest
     * @param servletResponse
     * @param filterChain
     * @throws IOException
     * @throws ServletException
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("进入了 doFilter 方法");
        long start = System.currentTimeMillis();
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("Execute cost="+(System.currentTimeMillis()-start));
    }

    @Override
    public void destroy() {
        System.out.println("进入了 destroy 方法");
    }
}

二者的方法都是访问controller为

package com.opendev.mystudy.Controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/test")
public class MyController  {

    @RequestMapping(value = "/frist",method = RequestMethod.GET)
    public void TestController() throws InterruptedException {
        System.out.println("-----------------");
        Thread.sleep(2000);
    }
}

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3.以上二者的分别使用，现在把他们二个集成使用看

从上面打印的日志就可以看，过滤器比拦截器先执行。

总结：过滤器比拦截器先执行