[hibernate-issues] [Hibernate-JIRA] Created: (HHH-3791) Primary Key class (@IdClass) used as object values and implies foreign key

[Timothy Twelves (JIRA)]

Primary Key class (@IdClass) used as object values and implies foreign key
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                 Key: HHH-3791
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3791
             Project: Hibernate Core
          Issue Type: Improvement
          Components: core, metamodel, query-hql
            Reporter: Timothy Twelves



As per: http://forums.hibernate.org/viewtopic.php?t=991417

Map primary key objects enforcing referential integrity without mapping the actual object.

This ensures that there is no possibility for lazy loading and also becomes nice for serialization and data transport.



{code:title=MyExample.java|borderStyle=solid}

@Entity
@IdClass(AccountPk.class)
class Account {
  long accountNo;
  PersonPk owner;                     // <----  here we refer many to one but using PersonPk instead of Person
}

class AccountPk {
  long accountNo;
}


class PersonPk {
  int person;
}

@Entity
@IdClass(PersonPk.class)
class Person {
  int id;
  AccountPk primaryAccount;
  Collection<AccountPk> accounts;  // <----  here we have one to many but using AccountPk instead of Account
}

{code}




The above example is insufficient as the PK object does not indicate its entity. @PrimaryEntity and @PrimaryEntityCollection is used below as an example how this would be marked appropriately.

{code:title=MyExample.java|borderStyle=solid}

@Entity
@IdClass(AccountPk.class)
class Account {
  long accountNo;

  @PrimaryEntity(entity=Person.class)
  PersonPk owner;
}

class AccountPk {
  long accountNo;
}


class PersonPk {
  int person;
}

@Entity
@IdClass(PersonPk.class)
class Person {
  int id;
  AccountPk primaryAccount;

  @PrimaryEntityCollection(entity=Person.class, primarykey=AccountPk.class)
  Collection<AccountPk> accounts;
}

{code}


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