JPA (Hibernate) issue with OneToOne mappedBy annot

问题:

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

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

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

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

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

Here are the entities

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
...

回答1:

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).

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:

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.

Here is a code example:

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

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