JPA（Hibernate）问题与OneToOne mappedBy注解 [英] JPA (Hibernate) issue with OneToOne mappedBy annotation

问题描述

在设置onetoOne关系时，我有两张表。
Bill和BillSimpleEntry。 （每个账单都有一个BillSimpleEntry

I have two tables for while I setup a oneToOne relationship. Bill and BillSimpleEntry. (Each Bill has one BillSimpleEntry

以下是他们的结构

Here is their structure

CREATE TABLE `bill` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  ..
  ..
  PRIMARY KEY (`id`),
  UNIQUE KEY `id_UNIQUE` (`id`),
  KEY `fk_bill_groups1_idx` (`groupId`),
  KEY `fk_bill_user1_idx` (`billPayerId`),
  CONSTRAINT `fk_b...` FOREIGN KEY (`groupId`) REFERENCES `groups` (`id`) ON D     ELETE  NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_b...` FOREIGN KEY (`billPayerId`) REFERENCES `user` (`id`) ON    DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;
/*!40101 SET character_set_client = @saved_cs_client */;



DROP TABLE IF EXISTS `billsimpleentry`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `billsimpleentry` (
  `..` varchar(200) DEFAULT NULL,
  `..` text,
  `billId` bigint(20) DEFAULT NULL,
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`),
  KEY `fk_bill_idx` (`billId`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

JPA配置（来自票据实体的oneToOne关系属性片段）。

JPA config (snippet from the bill Entity for the oneToOne relationship attribute).

@OneToOne(cascade=CascadeType.ALL,mappedBy="billId",fetch = FetchType.EAGER)
private BillSimpleEntry billSimpleEntry;

我试图通过billSimpleEntry.billId和bill.Id在Bill和BillSimpleEntry之间进行连接。但我似乎得到一个错误。

I'm trying to do a Join between Bill and BillSimpleEntry by billSimpleEntry.billId and bill.Id. But I seem to get an error.

这是我得到的错误 -

Here is the error I get-

Caused by: org.hibernate.AnnotationException: Referenced property not a (One|Many)ToOne:
com.uh.br.domain.BillSimpleEntry.billId in mappedBy of    
com.uh.br.domain.Bill.billSimpleEntryry

以下是实体

Bill.java
@Entity
@Table(name = "bill")
public class Bill implements GenericObject {

/**
 *
 */
private static final long serialVersionUID = -5660869020353250221L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)  
private Long id;

...
..
@OneToOne(cascade=CascadeType.ALL,fetch = FetchType.EAGER)
@JoinColumn(name="billId")
private BillSimpleEntry billSimpleEntry;

...
getters & setters
...
}

BillSimpleEntry.java
@Entity
@Table(name="billsimpleentry")
public class BillSimpleEntry  implements GenericObject{

@Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)  
    private Long id;
    private Long billId;
    @Column(columnDefinition="TEXT")
private String itemDescription;//napkin
...
...

    ...
getters & setters
...

推荐答案

mappedBy 属性仅对于双向关系是必需的，因此可以在注释中省略此元素。它在源实体上用于指向定义关系的目标实体上的字段（包含@JoinColumn）。

The mappedBy attribute is only necessary for a bidirectional relationship, this element can be omitted on the annotation. It is used on the source entity to point back to a field on the target entity that defines the relationship (contains @JoinColumn).

@ JoinColumn 注释应放置在 billSimpleEntry 字段上以定义应该用于连接两个表的列。在 OneToOne 的情况下适用：

The @JoinColumn annotation should be placed upon the billSimpleEntry field to define the column that should be used to join the two tables. In the case of a OneToOne the following applies:

如果连接是使用外键
映射策略的OneToOne或ManyToOne映射，外键列位于源
实体的表中或可嵌入。

If the join is for a OneToOne or ManyToOne mapping using a foreign key mapping strategy, the foreign key column is in the table of the source entity or embeddable.

$ b $

Here is a code example:

@OneToOne(cascade=CascadeType.ALL,fetch = FetchType.EAGER)
@JoinColumn(name="id")
private BillSimpleEntry billSimpleEntry;

另外，如果 Bill 包含 SimpleBillEntry 字段 BILL 表应该包含 billsimpleentry 表。

Also, if the Bill will contain the SimpleBillEntry field the BILL table should contain a foreign key to the billsimpleentry table.

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