doFilter是否登录状态验证和拦截

使用过滤器
过滤器要起作用，必须在主启动程序上加上@ServletComponentScan注解

@ServletComponentScan  //扫描WebFilter的注解

package com.tj.reggie.filter;
import com.alibaba.fastjson.JSON;
import com.tj.reggie.controller.utils.R;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.AntPathMatcher;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * 检查用户是否已经完成登录
 * "/*"是拦截所有访问
 */
@WebFilter(filterName = "loginCheckFilter", urlPatterns = "/*")
@Slf4j
public class LoginCheckFilter implements Filter {
    //路径匹配器，支持通配符
    public static final AntPathMatcher PATH_MATCHER = new AntPathMatcher();
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest; //转成http请求
        HttpServletResponse response = (HttpServletResponse) servletResponse;  //转成http响应
        //1.获取本次请求的URI
        String requestURI = request.getRequestURI();
        log.info("拦截到请求：{}", requestURI);
        //2.定义不需要处理的请求路径
        String[] uris = new String[]{
                "/users/login",
                "/users/logout",
                "/login.html",
                "/logout.html",
                "/img/**"
        };
        //3.判断本次请求是否需要处理
        boolean check = check(uris, requestURI);
        if (check) {
            //不需要处理的情况
            filterChain.doFilter(request, response);
            log.info("本次请求不需要处理：{}", requestURI);
            return;
        }
        //4.判断登录状态，如果已登录，则直接放行
        if (request.getSession().getAttribute("users") != null) {
            filterChain.doFilter(request, response);
            log.info("已经登录，用户id为：{}", request.getSession().getAttribute(("users")));
            return;
        }
        //5.如果未登录则返回未登录结果，通过输出流方式向客户端页面响应数据
        response.getWriter().write(JSON.toJSONString(R.error("NOTLOGIN")));
        log.info("未登录，返回响应数据：{}", requestURI);
        return;
    }
    /**
     * 路径匹配，检查本次请求是否需要放行
     *
     * @param uris
     * @param requestURI
     * @return
     */
    public boolean check(String[] uris, String requestURI) {
        for (String uri : uris) {
            boolean match = PATH_MATCHER.match(uri, requestURI);
            if (match) return true;
        }
        return false;
    }
}