Composite ID & Many To One Join

donlee8 · **Posted:** Fri Jan 23, 2009 7:04 pm

Hi,

I need some assistance on this (seemingly) simple mapping:

Tables:

Code:

security
    - securityId
    - ... more columns

Code:

company_security
    - companyId
    - securityId
    - rank

CompanySecurity.hbm.xml:

Code:

<composite-id>
    <key-many-to-one name="company" column="companyId" class="Company"/>
    <key-many-to-one name="security" column="securityId" class="Security"/>
</composite-id>
<property name="rank" column="rank"/>

Security.hbm.xml:

Code:

<id name="securityId" column="securityId">
    <generator class="increment"/>
</id>
<join table="company_security" inverse="true">
    <key column="security_id"/>
    <many-to-one name="companySecurity" column="companyId" class="CompanySecurity"/>
</join>

The structure calls for many securities associated with a single company, but only one company associated with a particular security. I can get the one-to-many mapping fine for Company -> CompanySecurity but the Security -> CompanySecurity mapping gives me this exception:

Code:

org.hibernate.MappingException: Foreign key (FK4F9028C25CCF0F1B:company_security [companySecurity])) must have same number of columns as the referenced primary key (company_security [companyId,securityId])

We're working with a legacy database so I can't change structure. Could someone give a beginner some pointers?

mmerder · **Posted:** Mon Jan 26, 2009 8:05 am

Quote:

Security.hbm.xml:

Code:

<id name="securityId" column="securityId">
    <generator class="increment"/>
</id>
<join table="company_security" inverse="true">
    <key column="security_id"/>
    <many-to-one name="companySecurity" column="companyId" class="CompanySecurity"/>
</join>

I think you can not use a <join> as Security has a one-to-many-association to CompanySecurity. Try to use a set or a bag instead.

donlee8 · **Posted:** Mon Jan 26, 2009 10:56 am

Is there a way to have a set or bag be a single item? I would not want my Security object to have Set<CompanySecurity> because this is confusing. Thanks for the help!

mmerder · **Posted:** Mon Jan 26, 2009 12:30 pm

I do not really understand what you need. Does one security only have one company?? I thought, companies can have many securities (with a different rank, so you need company_security) and securities can have many companies. So why do you need one company per security?

donlee8 · **Posted:** Mon Jan 26, 2009 1:01 pm

Sorry I wasn't clear. A Company can have many CompanySecurity objects (I have this mapping done using a <set> and it works great) but a Security can only have one CompanySecurity object (this is the mapping I can't get right). It's similar to the Parent/Child relationship in the Hibernate docs but with a join table. Company is the parent and Security is the child in this case.

mmerder · **Posted:** Mon Jan 26, 2009 1:09 pm

Ok, in that case you should not use a composite key in CompanySecurity.hbm.xml. If I understand your use case right, there is only one companySecurity per Security, so using only the securityId as primary key is the way to do it. So this relationship is actually a one-to-one(?)

donlee8 · **Posted:** Mon Feb 02, 2009 11:39 am

Thanks for the help. That worked. However I still need to persist the company first then add the CompanySecurity object:

Code:

Company company = new Company(... params ...);
new CompanyDao().create(company);
company.addSecurity(new CompanySecurity(company.getCompanyId,security.getSecurityId(),1));
session.flush();

Minor issue that i can live with (or possibly figure out how to resolve). Thanks again for the help