SpringBoot 使用 Filter 过滤器

 Filter 过滤器 是Java EE 提供的只能处理  ServletRequest 和 ServletResponse 里的相关信息，不能处理与Spring相关的信息

package com.example.interceptor;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import java.io.IOException;

@Component
public class DemoFilter implements Filter {
    private static final Logger logger = LoggerFactory.getLogger(DemoFilter.class);
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        logger.info("=========DemoFilter=======init==============");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        logger.info("=========DemoFilter=======doFilter==start============");

        filterChain.doFilter(servletRequest,servletResponse);//执行过滤

        logger.info("=========DemoFilter=======doFilter==end============");
    }

    @Override
    public void destroy() {
        logger.info("=========DemoFilter=======destroy==============");
    }
}

package com.example.config;

import com.example.interceptor.DemoFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

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

@Configuration//说明这是一个配置类
public class WebConfig {

    @Bean  //Bean注入，相当于原本在web.xml中写配置注入类
    public FilterRegistrationBean demoFilter(){
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();

        //在DemoFilter类上不用@Compent注入则可以用如下方法注入
        DemoFilter demoFilter = new DemoFilter();
        registrationBean.setFilter(demoFilter);
        List<String> urls = new ArrayList<>();
        urls.add("/*");//对所有url起作用
        registrationBean.setUrlPatterns(urls);

        return  registrationBean;
    }
}