完善登录功能

用户不登录不能访问系统其它页面，否则跳转到登录页面。

使用拦截器或过滤器，在拦截器或过滤器中判断用户是否已经完成登录，如果没有登录则跳转到登录页面。

（1）创建自定义过滤器（LoginCheckFilter）

package com.itheima.filter;

import lombok.extern.slf4j.Slf4j;

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
 */
@WebFilter(filterName = "loginCheckFilter", urlPatterns = "/*")
@Slf4j
public class LoginCheckFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse; 
        log.info("拦截到请求: {}", request.getRequestURI());
        filterChain.doFilter(request, response);
    }   


}

（2）在启动类上加入注解@ServletComponentScan

package com.itheima;

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.ComponentScan;

@Slf4j
@SpringBootApplication
@ServletComponentScan
public class ReggieTakeOutApplication {

    public static void main(String[] args) {

        SpringApplication.run(ReggieTakeOutApplication.class, args);
        log.info("项目启动成功");
    }

}

（3）完善过滤器的处理逻辑

package com.itheima.filter;

import com.alibaba.fastjson.JSON;
import com.itheima.common.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 javax.servlet.http.HttpSession;
import java.io.IOException;


/**
 * 检查用户是否已经完成登录
 */
@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;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        //1、获取本次请求的URI
        String requestURI = request.getRequestURI();
        log.info("拦截到请求:{}", requestURI);
        //定义不需要处理的请求路径
        String[] urls = new String[]{
                "/employee/login",
                "/employee/logout",
                "/backend/**",
                "/front/**"
        };

        //2、判断本次请求是否需要处理
        boolean check = check(urls, requestURI);
        // 3、如果不需要处理，则直接放行
        if(check){
            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("employee")!=null){
            filterChain.doFilter(request, response);
            log.info("用户已登录,用户id为：{}", request.getSession().getAttribute("employee"));
            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响应数据
        response.getWriter().write(JSON.toJSONString(R.error("NOTLOGIN")));
        log.info("用户未登录:{}", requestURI);
        return;


    }


    /**
     * 路径匹配，检查本次请求是否需要放行
     */
    public boolean check(String urls[], String requestURI){
        for(String url : urls){
            boolean match = PATH_MATCHER.match(url, requestURI);
            if(match){
                return  true;
            }
        }
        return  false;
    }


}