一、环境准备（模拟数据库的情况）

1.pojo

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Employee {     //  员工表
    private Integer id;
    private String lastName;
    private String email;
    private Integer gender;
    private Department department;
    private Date birth;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Department {       //  部门表
    private Integer id;
    private String departmentName;
}