一.spring的filter是作用在interceptor（拦截器）之前，filter主要是依赖serlvet容器

二.filter怎样在spring中的使用

2.1只用自定义的过滤器（使用WebFilter要使用ServletComponentScan注解，不然会失效）
实现java.servlet.filter接口

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

@Component
@WebFilter(filterName="myFilter",urlPatterns = "/*")
public class MyFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        filterChain.doFilter(servletRequest,servletResponse);
    }
}

@SpringBootApplication
@ComponentScan(value = "com.example")
@ServletComponentScan   //扫描过滤器
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

继承springframework.web.filter.oncePerRequestFilter(同样是要使用@ServletComponentScan)

import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter //继承OncePerRequestFilter的过滤的类，对每个请求只会过滤一次，这也是与实现Filter类不一样的地方
public class MyOnceProRequestFilter extends OncePerRequestFilter {
    @Override
    protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException {
        filterChain.doFilter(httpServletRequest,httpServletResponse);
    }
}

2.2注册自己自定义的过滤器

写一个配置类（使用Configuration），使用@Bean注入

@Configuration  //表示这是一个设置类
public class MyRegistration {

    @Bean
    public FilterRegistrationBean MyRegistrationBean(MyFilter myFilter){
        FilterRegistrationBean<Filter> registrationBean = new FilterRegistrationBean<>();
        registrationBean.setFilter(myFilter);   //设置过滤器
        registrationBean.setUrlPatterns(Collections.singleton("/*")); //设置过滤路径
        registrationBean.setOrder(1);  //设置优先级
        return registrationBean;
    }
}