mybatis 一对多查询

mybatis 一对多查询

一、实体类

//一个部门对应多个员工
public class Dept {
    private Integer deptid;
    private String dname;
    private String dloc;
    private Set<Emp> emps= new HashSet<>();
}
public class Emp {
    private Integer empid;
    private String ename;
    private String esex;
    private Date ehiredate;
    private Double esal;
    private Dept dept;
}

二、接口方法

public interface DeptMapper {
    
    @Select("select * from dept ")
    @Results({@Result(property = "deptid" ,column = "deptid"),
        @Result(property = "dname" ,column = "dname"),
        @Result(property = "dloc" ,column = "dloc"),
        @Result(property = "emps",javaType = Set.class, column = "deptid",
        many = @Many(select="com.gx.mapper.EmpMapper.selectEmpByDeptId"))
        }) //调用方法的全路径+方法名
    public List<Dept> selectAll();
}

public interface EmpMapper {
    /**
     * 根据部门id查询员工信息
     */
    @Select("select * from emp where deptid=#{deptid}")
    public List<Emp>selectEmpByDeptId(Integer deptid);
}