Question

我有以下课程：

@Entity
@Table(name = "PARENT")
public class Parent {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "PARENT_ID", unique = true, nullable = false, insertable = true, updatable = true)
private Long parentId;


@OneToMany(cascade = {CascadeType.ALL}, fetch = FetchType.EAGER ) 
@JoinColumn(name="PARENT_ID", nullable = false)
private List<Child> children;


public Parent(List<Child> children) {
this.children = children;
}


..
... Getters\Setters

}


@Entity
@Table(name = "CHILD")
public class Child {

@Id 
@Column(name = "TYPE", unique = false, nullable = false)
private String type;

@Column(name = "RANK", unique = false, nullable = false, insertable = true, updatable = false)
private String rank;

}

'PARENT_ID'是“CHILD”表中的外键。所以它使“CHILD”表有2列形成它的PRIMARY_KEY。

我执行以下插入：

List<Child> children = new LinkedList<Child>();
children.add(new Child("1,2,3,4"));
children.add(new Child("1,2,3,4"));

Parent parent = new Parent(children);

session.save(parent);

如果两个表都为空，则通过分配PARENT_ID！， BUT 来正确创建“父”和“子”，如果表中已存在“子”条目，则表示执行更新而不是插入！ / p>

注意两个'孩子'都有相同的“TYPE”（“1,2,3,4”），但他们应该有不同的“PARENT_ID”。

我在这里错过了什么????

谢谢！

Answer 1

在您的孩子中，您需要拥有父母的实例，并且我相信您错误地放置了您的子类中的JoinColumn，该类应该在您的子类中。在您的Parent类中不需要构造函数。

父类应该类似于：

@Entity
@Table(name = "PARENT")
public class Parent {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "PARENT_ID", unique = true, nullable = false, insertable = true,          updatable = true)
private Long parentId;


@Embedded
private Child children;


..
... Getters\Setters (MAke sure you have the getter setter for children as well)

}

您的Child类应该是这样的：

@Embeddable
@Table(name = "CHILD")
public class Child {

@Id 
@Column(name = "TYPE", unique = false, nullable = false)
private String type;

@Column(name = "RANK", unique = false, nullable = false, insertable = true, updatable = false)
private String rank;


    //getter and setters

具有外键的单向OneToMany不会插入到表中

1 个答案: