CODEWITHSUNDEEP
javahibernateprimary-keycomposite-primary-key
Pete B.
Pete B.

Reputation: 3286

Using Hibernate Get with Multi-Column Primary Key

Say I have a class that looks like this:

public class MyClass {
  @Id
  @Column(name = "ID")
  private long Id;
}

I can use a hibernate session to do a get or load on the class like this:

MyClass a = (MyClass)session.get(MyClass.class, new Long(100));

However, assume I have a class with multiple columns as the primary key:

public MyJoinClass implements Serializable {
  private static final long serialVersionUID = -5L;
  @Id
  @Column(name = "ID")
  private long id;

  @Id
  @Column(name = "EMAIL_ADDRESS_ID")
  private long emailAddressId;
}

Is it possible to use get or load with such a class?

Upvotes: 6

Views: 16302

Answers (2)

dpelisek
dpelisek

Reputation: 1031

In Hibernate yes (documentation):

MyJoinClass a = session.get(MyJoinClass.class, new MyJoinClass(100, 200));

Just make sure to have a constructor with all parts of the composite key (and don't forgot the default public constructor with no parameters):

public MyJoinClass implements Serializable {
  private static final long serialVersionUID = -5L;
  @Id
  @Column(name = "ID")
  private long id;

  @Id
  @Column(name = "EMAIL_ADDRESS_ID")
  private long emailAddressId;

  public MyJoinClass() {}

  public MyJoinClass(long id, long emailAddressId) {
    this.id= id;
    this.emailAddressId= emailAddressId;
  }
}

Upvotes: 1

Koitoer
Koitoer

Reputation: 19533

Try to use and @IdClass or @EmbeddedId

public MyJoinClass implements Serializable {
  private static final long serialVersionUID = -5L;

  @EmbeddedId
  private MyJoinClassKey key;
}

public MyJoinClassKey implements Serializable{

  @Column(name = "ID")
  private long id;

  @Column(name = "EMAIL_ADDRESS_ID")
  private long emailAddressId;
}

Then use 

MyJoinClass a = (MyJoinClass )session.get(MyJoinClass .class, new MyJoinClassKey (1, "email"));

Take a look at this question, this is broadly explained. Basically hibernate have a mechanism for compound keys.

Upvotes: 9

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