Spring的OncePerRequestFilter过滤器用法解读

package com.fchan.espractice.filter;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.annotation.Order;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

@Component
@Order(-1000)
public class MyOnceFilter extends OncePerRequestFilter {

    @Autowired
    private ObjectMapper objectMapper;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        String token = request.getHeader("token");
        if(!StringUtils.isEmpty(token)){
            filterChain.doFilter(request, response);
        }

        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        response.setContentType(MediaType.APPLICATION_JSON_UTF8_VALUE);
        Map<String,Object> map = new HashMap<>();
        map.put("name","李四");
        ServletOutputStream outputStream = response.getOutputStream();
        outputStream.write(objectMapper.writeValueAsBytes(map));
        outputStream.close();
        //重定向之后还是会进入过滤器的
        //response.sendRedirect("/testQuery");
    }
}