Question

我试图找出用于建模JPA实体字段的适当关系，该实体字段需要查找表（在UI上等效的Comboxbox）来从中选择值。以下示例：

@Entity
public class Employee {

    @Id
    private int employeeId;
    private String name;
    private Department department;
}

@Entity
public class Department  {

    @Id
    private int id;
    private String name;
}

部门的实例可以如下：

Id    | Name
-----------------------
100   | Human Resources
101   | Sales
102   | Finances

对于员工，部门字段应从上述之一获取值。两个实体中相应字段的JPA注释应该是什么？

谢谢，

Sandeep Joseph

Answer 1

我认为您正在寻找从Employee到Department的单向ManyToOne关系，如下所示：

@Entity
public class Employee {

    @Id
    private int employeeId;
    private String name;

    @ManyToOne
    @JoinColumn(name = "department_id", nullable = false)
    private Department department;
}

这意味着员工必须与单个部门相关联，部门可以与许多员工相关联。

如果您需要知道与某个部门相关联的员工列表，那么您可以通过添加以下内容来建立双向关系：

@Entity
public class Department  {

    @Id
    private int id;
    private String name;

    @OneToMany(mappedBy = "department")
    private Collection<Employee> employees; 
}

JPA实体字段的模型查找表

1 个答案: