mybatis处理多对一映射关系1 - 通过联级属性赋值解决多对一映射关系

1.数据库关系

SELECT * FROM mybaits.t_emp;

SELECT * FROM mybaits.t_dept;

 

2.POJO实体类添加Dept信息

定义dept属性，get set方法，重写tostring方法

package com.mybatis.pojo;

public class Emp {

    private Integer eid;

    private String empName;

    private Integer age;

    private String sex;

    private String email;

    private Dept dept;

    public Emp(Integer eid, String empName, Integer age, String sex, String email) {
        this.eid = eid;
        this.empName = empName;
        this.age = age;
        this.sex = sex;
        this.email = email;
    }

    public Emp() {
    }

    public Integer getEid() {
        return eid;
    }

    public void setEid(Integer eid) {
        this.eid = eid;
    }

    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 getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "eid=" + eid +
                ", empName='" + empName + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                ", email='" + email + '\'' +
                ", dept=" + dept +
                '}';
    }

    public Dept getDept() {
        return dept;
    }

    public void setDept(Dept dept) {
        this.dept = dept;
    }
}

3.接口

    /**
     * 查询员工和对应部门信息
     */
    Emp getEmpAndDept(@Param("eid") Integer eid);

4. Mapper映射文件 4.1映射细节

    
        select * from t_emp left join t_dept on t_emp.did = t_dept.did where t_emp.eid = #{eid}
    

4.2自定义resultMap 

5.测试类

    @Test
    public void testGetOneEmpAndDept(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);
        Emp empAndDept = mapper.getEmpAndDept(1);
        System.out.println(empAndDept);

    }

 6.结果