修改Mappper文件

EmployeeMapper
//希望查询员工的同时部门信息也是查询好的
    private Department department;
    public void setDepartment(Department department) {
        this.department = department;
    }
    public Department getDepartment() {
        return department;
    }

自定义resultMap

  <resultMap id="BaseResultMap" type="com.atguigu.crud.bean.Employee">
    <id column="emp_id" jdbcType="INTEGER" property="empId" />
    <result column="emp_name" jdbcType="VARCHAR" property="empName" />
    <result column="gender" jdbcType="CHAR" property="gender" />
    <result column="eamil" jdbcType="VARCHAR" property="eamil" />
    <result column="d_id" jdbcType="INTEGER" property="dId" />
  </resultMap>
  <!--自定义resultMap-->
  <resultMap id="WithDeptResultMap" type="com.atguigu.crud.bean.Employee">
    <id column="emp_id" jdbcType="INTEGER" property="empId" />
    <result column="emp_name" jdbcType="VARCHAR" property="empName" />
    <result column="gender" jdbcType="CHAR" property="gender" />
    <result column="eamil" jdbcType="VARCHAR" property="eamil" />
    <result column="d_id" jdbcType="INTEGER" property="dId" />
    <!--指定联合查询出的部门字段的封装-->
    <association property="department" javaType="com.atguigu.crud.bean.Department">
      <id column="dept_id" property="deptId"></id>
      <result column="dept_name" property="deptName"></result>
    </association>
  </resultMap>

  <sql id="Base_Column_List">
    emp_id, emp_name, gender, eamil, d_id
  </sql>
  <sql id="WithDept_Column_List">
    e.emp_id, e.emp_name, e.gender, e.eamil, e.d_id, d.dept_id, d.dept_name
  </sql>
<!--  List<Employee> selectByExampleWithDept(EmployeeExample example);

  Employee selectByPrimaryKeyWithDept(Integer empId);-->
  <select id="selectByPrimaryKeyWithDept" resultMap="WithDeptResultMap">
    select
    <include refid="WithDept_Column_List" />
    from tbl_emp
    left join tbl_dept d on e.d_id = d.dept_id
    where emp_id = #{empId,jdbcType=INTEGER}
  </select>
  <select id="selectByExampleWithDept" resultMap="WithDeptResultMap">
    select
    <if test="distinct">
      distinct
    </if>
    <include refid="WithDept_Column_List" />
    from tbl_emp e
    left join tbl_dept d on e.d_id = d.dept_id
    <if test="_parameter != null">
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null">
      order by ${orderByClause}
    </if>
  </select>
  <select id="selectByExample" parameterType="com.atguigu.crud.bean.EmployeeExample" resultMap="BaseResultMap">
    select
    <if test="distinct">
      distinct
    </if>
    <include refid="Base_Column_List" />
    from tbl_emp
    <if test="_parameter != null">
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null">
      order by ${orderByClause}
    </if>
  </select>
  <select id="selectByPrimaryKey" parameterType="java.lang.Integer" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from tbl_emp
    where emp_id = #{empId,jdbcType=INTEGER}
  </select>