Java mappingBy 引用了一个未知的目标实体属性
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mappedBy reference an unknown target entity property
提问by boyd4715
I am having an issue in setting up a one to many relationship in my annotated object.
我在带注释的对象中设置一对多关系时遇到问题。
I have the following:
我有以下几点：
@MappedSuperclass
public abstract class MappedModel
{
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id",nullable=false,unique=true)
private Long mId;
then this
那么这个
@Entity
@Table(name="customer")
public class Customer extends MappedModel implements Serializable
{
/**
*
*/
private static final long serialVersionUID = -2543425088717298236L;
/** The collection of stores. */
@OneToMany(mappedBy = "customer", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Collection<Store> stores;
and this
和这个
@Entity
@Table(name="store")
public class Store extends MappedModel implements Serializable
{
/**
*
*/
private static final long serialVersionUID = -9017650847571487336L;
/** many stores have a single customer **/
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn (name="customer_id",referencedColumnName="id",nullable=false,unique=true)
private Customer mCustomer;
what am i doing incorrect here
我在这里做错了什么
采纳答案by Pascal Thivent
The mappedByattribute is referencing customerwhile the property is mCustomer, hence the error message. So either change your mapping into:
当mappedBy属性为customer时，该属性正在引用mCustomer，因此会出现错误消息。因此，要么将您的映射更改为：
/** The collection of stores. */
@OneToMany(mappedBy = "mCustomer", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
private Collection<Store> stores;
Or change the entity property into customer(which is what I would do).
或者将实体属性更改为customer（这是我要做的）。
The mappedBy reference indicates "Go look over on the bean property named 'customer' on the thing I have a collection of to find the configuration."
mappingBy 引用表示“在我收集的事物上查看名为‘customer’的 bean 属性以查找配置。”
回答by Dhyanesh
I know the answer by @Pascal Thiventhas solved the issue. I would like to add a bit more to his answer to others who might be surfing this thread.
我知道@Pascal Thivent的回答已经解决了这个问题。我想在他对可能浏览此线程的其他人的回答中添加更多内容。
If you are like me in the initial days of learning and wrapping your head around the concept of using the @OneToManyannotation with the 'mappedBy' property, it also means that the other side holding the @ManyToOneannotation with the @JoinColumnis the 'owner' of this bi-directional relationship.
如果你和我一样，在刚开始学习的时候，对使用@OneToMany带有 ' mappedBy' 属性的注解的概念感到头疼，这也意味着持有@ManyToOne带有@JoinColumn'的注解的另一边是这个双向的“所有者”关系。
Also, mappedBytakes in the instance name(mCustomerin this example) of the Class variable as an input and not the Class-Type(ex:Customer) or the entity name(Ex:customer).
此外，mappedBy将类变量的实例名称（mCustomer在本例中）作为输入，而不是类类型（例如：客户）或实体名称（例如：客户）。
BONUS :
Also, look into the orphanRemovalproperty of @OneToManyannotation. If it is set to true, then if a parent is deleted in a bi-directional relationship, Hibernate automatically deletes it's children.
奖励：另外，查看注释的orphanRemoval属性@OneToMany。如果设置为 true，那么如果在双向关系中删除了父级，Hibernate 会自动删除它的子级。
