How to update foreign key on associated entity?

Arron.Ferguson · **Joined:** Fri Jul 25, 2008 5:22 am **Posts:** 12

I have a one-to-one bidirectional relationship using the foreign key as:

member(id, ...)
memberaddress(id, ...)

The member has:

Code:

public class Member ...
{
...
    @Id
    @Column(name = "member_id")
    @GeneratedValue(strategy = AUTO)
    public int getId() {
        return id;
    }

    @OneToOne(optional = true, cascade = ALL, fetch = EAGER)
    @JoinColumn(name="member_id", unique = true, updatable = false)
    public MemberAddress getMemberAddress()
    {
        return memberAddress;
    }
...
}

The member address has:

Code:

public class MemberAddress ...
{
    @OneToOne(mappedBy = "memberAddress")
    public Member getMember()
    {
        return member;
    }

    @Id
    @Column(name = "member_id", updatable= false, unique = true)
    public int getId()
    {
        return id;
    }
...
}

In my application I call:

Code:

  // Member newMember = Member();
  ...
  MemberAddress ma = new
   stateOrProvince, zipOrpostalCode);
  ma.setId(newMember.getId());
  newMember.setMemberAddress(ma);
  ma.setMember(newMember);
  em.persist(newMember);

Both entities are updated to the MySQL DB. However, the MemberAddress id value (foreign/primary key) is not updated (it still has the -1 value that was set during construction).

How do I get Hibernate to update the weak entity MemberAddress's foreign key which references the parent entity? And actually I thought with all the annotations I was using, that this was suppose to be already taken care of for me. Or am I missing something?

Any help most appreciated.

Arron.Ferguson · **Joined:** Fri Jul 25, 2008 5:22 am **Posts:** 12

I've actually noticed that Hibernate isn't doing what the documentation says the annotations should do since after I run my application, I get this from the MySQL DB:

Code:

CREATE TABLE `memberaddress` (
  `member_id` int(11) NOT NULL,
  `mailingaddress` varchar(255) default NULL,
  `stateorprovince` varchar(255) default NULL,
  `ziporpostalcode` varchar(255) default NULL,
  PRIMARY KEY  (`member_id`)

FYI: I get the above DDL by running:

Code:

mysqldump -u mysqlaccount -p mydb --no-data > script_file.sql

andydale · **Posted:** Wed Aug 06, 2008 4:22 am

Hi,

I think the foreign key will be in the member table (member is the owning side of the realtionship). You should change you entities as follows:

Code:

public class Member ... 
{ 
... 
    @Id 
    @Column(name = "member_id") 
    @GeneratedValue(strategy = AUTO) 
    public int getId() { 
        return id; 
    } 

    @OneToOne(optional = true, cascade = ALL, fetch = EAGER) 
    public MemberAddress getMemberAddress() 
    { 
        return memberAddress; 
    } 
... 
}

public class MemberAddress ... 
{ 
    @OneToOne(mappedBy = "memberAddress") 
    public Member getMember() 
    { 
        return member; 
    } 

    @Id 
    @GeneratedValue(strategy = AUTO)
    public int getId() 
    { 
        return id; 
    } 
... 
}

You can add the additional @Column annotations if you desire.

The above setup generates the following DDL:

Code:

CREATE TABLE member
(
  member_id int4 NOT NULL,
  memberaddress_member_id int4,
  CONSTRAINT member_pkey PRIMARY KEY (member_id),
  CONSTRAINT fk892776ba9c783481 FOREIGN KEY (memberaddress_member_id)
      REFERENCES memberaddress (member_id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)

CREATE TABLE memberaddress
(
  member_id int4 NOT NULL,
  CONSTRAINT memberaddress_pkey PRIMARY KEY (member_id)
)

Cheers,

Andy

Arron.Ferguson · **Joined:** Fri Jul 25, 2008 5:22 am **Posts:** 12

andydale wrote:

Hi,

I think the foreign key will be in the member table (member is the owning side of the realtionship). You should change you entities as follows:
...
Cheers,

Andy

Andy, thanks for your time. That does work although it has an extra id value in the member table (which thus breaks normalization because it contains nulls). My idea was that the weak entity should use the primary key of the parent entity. That is to say: the address table should have its primary key set as the foreign key reference to the member table. The problem is that the Hibernate documentation makes absolutely no mention whatsoever of how to force the weak entity to set its primary key as a foreign key to the parent table (at least not using annotations).

I did find a solution from a post made by Hibernate forum user efriedman (half way down the page) at:

http://forum.hibernate.org/viewtopic.php?p=2367400

It uses GenericGenerator with a foreign strategy. His solution generates the following in MySQL:

Code:

DROP TABLE IF EXISTS `address`;
CREATE TABLE `address` (
  `id` bigint(20) NOT NULL,
  `mem_city` varchar(255) default NULL,
  PRIMARY KEY  (`id`),
  KEY `FKBB979BF42EA0FBC4` (`id`)
)

DROP TABLE IF EXISTS `member`;
CREATE TABLE `member` (
  `id` bigint(20) NOT NULL auto_increment,
  `mem_name` varchar(255) default NULL,
  PRIMARY KEY  (`id`)
)

Thus, if a member is generated, its primary key value is trickled down to the weak entity. But thanks, your solution also works - it's just another perspective.

:)