mybatis：自定义映射关系resultMap

创建表t_emp

定义实体类

package org.example.entity;

public class Emp {
    private Integer empId;
    private String empName;
    private Integer age;
    private String gender;
    private Integer deptId;

    public Emp() {
    }

    public Emp(Integer empId, String empName, Integer age, String gender, Integer deptId) {
        this.empId = empId;
        this.empName = empName;
        this.age = age;
        this.gender = gender;
        this.deptId = deptId;
    }

    public Integer getEmpId() {
        return empId;
    }

    public void setEmpId(Integer empId) {
        this.empId = empId;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Integer getDeptId() {
        return deptId;
    }

    public void setDeptId(Integer deptId) {
        this.deptId = deptId;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "empId=" + empId +
                ", empName='" + empName + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                ", deptId=" + deptId +
                '}';
    }
}

mapper接口

public interface EmpMapper {

   public Emp queryEmpById(@Param("id") int id);
}

EmpMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.example.mapper.EmpMapper">

    <!--
        resultMap：设置自定义映射关系
        id：唯一标识
        type：处理映射关系的实体类的类型
        常用的标签：
        id：处理主键和实体类中属性的映射关系
        result：处理普通字段实体类中属性的映射关系
        column：设置映射关系中的字段名，必须是sql查询出的某个字段
        property：设置映射关系中的属性的属性名，必须是处理的实体类类型中的属性名
    -->
    <resultMap id="empResultMap" type="emp">
        <id column="emp_id" property="empId"></id>
        <result column="emp_name" property="empName"></result>
        <result column="age" property="age"></result>
        <result column="gender" property="gender"></result>
        <result column="dept_id" property="deptId"></result>
    </resultMap>

    <select id="queryEmpById" resultMap="empResultMap">
        select * from t_emp where emp_id = #{id}
    </select>
</mapper>

测试代码

    @Test
    public void queryEmpById(){
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
        Emp emp = mapper.queryEmpById(2);
        System.out.println(emp);

        sqlSession.close();
    }