CODEWITHSUNDEEP
hibernatejpamappingjpa-2.0
Dave
Dave

Reputation: 19150

JPA mapping: Foreign key must have same number of columns in the referenced primary key

I’m using JPA 2.0 with Hibernate 4.1.0.Final. I’m having trouble figuring out how to Map a couple of entities. I have a Group and a GroupMember class, but the following mappings …

@Entity
@Table(name = "group")
public class Group    
{
    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;
    …

    @ManyToMany
    @ElementCollection
    @CollectionTable(name="group_member", joinColumns=@JoinColumn(name="GROUP_ID"))
    private Set<GroupMember> members;




@Entity
@Table(name = "group_member")
public class GroupMember
{

    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;
    …

    @ManyToOne
    @JoinColumn(name = "GROUP_ID", nullable = false, updatable = true)
    private Group group;

result in this exception …

Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:914)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:889)
    at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:73)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:287)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:310)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1514)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1452)
    ... 38 more
Caused by: org.hibernate.MappingException: Foreign key (FK4719AC489E4DD84:group_member [members_ID])) must have same number of columns as the referenced primary key (group_member [GROUP_ID,members_ID])
    at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:110)
    at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:93)
    at org.hibernate.cfg.Configuration.secondPassCompileForeignKeys(Configuration.java:1704)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1627)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1362)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1727)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:88)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:904)

How do I map my GroupMembers field into my Group class?

    ... 44 more

Upvotes: 0

Views: 8360

Answers (1)

Alan Hay
Alan Hay

Reputation: 23226

The issue is that you have a @OneToMany on one side and @ManyToMany on the other. Additionally @ElementCollection and @CollectionTable are the wrong annotations in this case as your are dealing with a collection of Entities rather than Embeddables:

http://en.wikibooks.org/wiki/Java_Persistence/ElementCollection

If the model is such that one Group can have many Members and a Member can belong to many Groups then you have two options. You can use @ManyToMany Group <> Member (and use @JoinTable to define the Join table) or, you can define an intermediate entity for the join and map the relationships as @OneToMany.

The latter is the recommended approach as it will allow you to store extra information about the relationship: for example, in this case you could define an extra field on GroupMember to store the date the Member joined the Group.

@Entity
@Table(name = "group")
public class Group    
{
    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;
    …

    @OneToMany(mappedBy = "group")
    private Set<GroupMember> members;
}

@Entity
@Table(name = "member")
public class Member    
{
    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;
    …

    @OneToMany(mappedBy = "member")
    private Set<GroupMember> groups;
}

@Entity
@Table(name = "group_member")
public class GroupMember
{

    @Id
    @NotNull
    @GeneratedValue(generator = "uuid-strategy")
    @Column(name = "ID")
    private String id;
    …

    @ManyToOne
    @JoinColumn(name = "GROUP_ID", nullable = false, updatable = true)
    private Group group;

    @ManyToOne
    @JoinColumn(name = "MEMBER_ID", nullable = false, updatable = true)
    private Member member;
}

Upvotes: 2

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