Bagaimana untuk melaksanakan fungsi log masuk backend Java

package com.itheima.reggie.common;
import lombok.Data;
import java.util.HashMap;
import java.util.Map;
/**
 * 返回通用类
 * @author jekong
 * @date 2022/4/22
 */
@Data
public class R<T> {
    /** 编码：1成功，0和其它数字为失败*/
    private Integer code;
    /** 信息返回*/
    private String msg;
    /** 信息返回数据*/
    private T data;
    /** 动态数据*/
    private Map map = new HashMap();
    public static <T> R<T> success(T object) {
        R<T> r = new R<T>();
        r.data = object;
        r.code = 1;
        return r;
    }
    public static <T> R<T> error(String msg) {
        R r = new R();
        r.msg = msg;
        r.code = 0;
        return r;
    }
    public R<T> add(String key, Object value) {
        this.map.put(key, value);
        return this;
    }
}

package com.itheima.reggie.entity;
import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.annotation.TableField;
import lombok.Data;
import java.io.Serializable;
import java.time.LocalDateTime;
/**
 * 员工实体类
 * @author jektong
 * @date 2022/4/21
 */
@Data
public class Employee implements Serializable {
    /** 序列号*/
    private static final long serialVersionUID = 1L;
    /**唯一主键*/
    private Long id;
    /**用户名*/
    private String username;
    /**姓名*/
    private String name;
    /**密码*/
    private String password;
    /**电话*/
    private String phone;
    /**性别*/
    private String sex;
    /**身份证号码*/
    private String idNumber;
    /**状态*/
    private Integer status;
    /**创建时间*/
    private LocalDateTime createTime;
    /**更新时间*/
    private LocalDateTime updateTime;
    /**添加用户时使用*/
    @TableField(fill = FieldFill.INSERT)
    private Long createUser;
    /**更新用户时使用*/
    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Long updateUser;
}

package com.itheima.reggie.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itheima.reggie.entity.Employee;
import org.apache.ibatis.annotations.Mapper;
/**
 * EmployeeMapper
 * @author jektong
 * @date 2022/4/21
 */
@Mapper
public interface EmployeeMapper extends BaseMapper<Employee> {
}

package com.itheima.reggie.service;
import com.baomidou.mybatisplus.extension.service.IService;
import com.itheima.reggie.entity.Employee;
import org.springframework.stereotype.Service;
/**
 * @author jektong
 * @date 2022/4/21
 */
public interface EmployeeService extends IService<Employee> {
}

package com.itheima.reggie.service.impl;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.itheima.reggie.entity.Employee;
import com.itheima.reggie.mapper.EmployeeMapper;
import com.itheima.reggie.service.EmployeeService;
import org.springframework.stereotype.Service;
/**
 * @author jektong
 * @date 2022/4/21
 */
@Service
public class EmployeeServiceImpl extends ServiceImpl<EmployeeMapper, Employee> implements EmployeeService {
}

package com.itheima.reggie.controller;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.itheima.reggie.common.CommonsConst;
import com.itheima.reggie.common.R;
import com.itheima.reggie.entity.Employee;
import com.itheima.reggie.service.EmployeeService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.DigestUtils;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
/**
 * 员工控制类
 *
 * @author tongbing
 * @date 2022/4/21
 */
@Slf4j
@RestController
@RequestMapping("/employee")
public class EmployeeController {
    @Resource
    private EmployeeService employeeService = null;
    /**
     * 登录请求处理
     * TODO 后续改进将业务处理的代码放入业务层，这里只做数据请求与返回
     * @param request
     * @param employee
     * @return
     */
    @PostMapping("/login")
    public R<Employee> login(HttpServletRequest request,
                             @RequestBody Employee employee) {
        // 将页面提交的密码进行MD5加密
        String password = employee.getPassword();
        password = DigestUtils.md5DigestAsHex(password.getBytes());
        // 根据用户名查数据库
        LambdaQueryWrapper<Employee> queryWrapper = new LambdaQueryWrapper<Employee>();
        queryWrapper.eq(Employee::getUsername, employee.getUsername());
        Employee emp = employeeService.getOne(queryWrapper);
        // 查不到返回登录失败结果
        if(emp == null){
            return R.error(CommonsConst.LOGIN_FAIL);
        }
        // 比对密码
        if(!emp.getPassword().equals(password)){
            return R.error(CommonsConst.LOGIN_FAIL);
        }
        // 查看员工状态
        if(emp.getStatus() == CommonsConst.EMPLOYEE_STATUS_NO){
            return R.error(CommonsConst.LOGIN_ACCOUNT_STOP);
        }
        // 登录成功将员工的ID放入session中
        request.getSession().setAttribute("employeeId",emp.getId());
        return R.success(emp);
    }
}

package com.itheima.reggie.common;
/**
 * 常量定义
 * @author jektong
 * @date 2022/4/23
 */
public class CommonsConst {
    // 登录失败
    public static final String LOGIN_FAIL = "登录失败";
    // 账号禁用
    public static final String LOGIN_ACCOUNT_STOP = "账号禁止使用";
    // 员工账号禁用状态 0：禁用
    public static final Integer EMPLOYEE_STATUS_NO = 0;
    // 员工账号正常状态 1：正常使用
    public static final Integer EMPLOYEE_STATUS_YES = 1;
}