how to make a composite primary key (java persistence annotation)

by

You’ve already had a few good answers here on how to do exactly as you ask..

For reference let me just mention the recommended way to do this in Hibernate instead, which is to use a surrogate key as primary key, and to mark business keys as NaturalId’s:

Although we recommend the use of
surrogate keys as primary keys, you
should try to identify natural keys
for all entities. A natural key is a
property or combination of properties
that is unique and non-null. It is
also immutable. Map the properties of
the natural key inside the
element. Hibernate will
generate the necessary unique key and
nullability constraints and, as a
result, your mapping will be more
self-documenting.

It is recommended that you implement
equals() and hashCode() to compare the
natural key properties of the entity.

In code, using annotations, this would look something like this:

@Entity
public class UserRole {
  @Id
  @GeneratedValue
  private long id;

  @NaturalId
  private User user;
  @NaturalId
  private Role role;
}

Using this will save you a lot of headaches down the road, as you’ll find out when you frequently have to reference / map the composed primary key.

I found this out the hard way, and in the end just gave up fighting against Hibernate and instead decided to go with the flow. I fully understand that this might not be possible in your case, as you might be dealing with legacy software or dependencies, but I just wanted to mention it for future reference. (if you can’t use it maybe someone else can!)

More Related Contents:

  1. Name attribute in @Entity and @Table
  2. Setting a JPA timestamp column to be generated by the database?
  3. Only using @JsonIgnore during serialization, but not deserialization
  4. Xml configuration versus Annotation based configuration [closed]
  5. Is it possible to read the value of a annotation in java?
  6. Java Annotations values provided in dynamic manner
  7. What is the use of marker interfaces in Java?
  8. Should we @Override an interface’s method implementation?
  9. Which types can be used for Java annotation members?
  10. How do different retention policies affect my annotations?
  11. JFreechart series tool tip above shape annotation
  12. Why doesn’t a missing annotation cause a ClassNotFoundException at runtime?
  13. Difference Between One-to-Many, Many-to-One and Many-to-Many?
  14. Hibernate : How override an attribute from mapped super class
  15. Retrieve Java Annotation Attribute
  16. How to scan multiple paths using the @ComponentScan annotation?
  17. @OneToMany and composite primary keys?
  18. Java String validation using enum values and annotation
  19. Error setting a default null value for an annotation’s field
  20. intellij incorrectly saying no beans of type found for autowired repository
  21. Annotating the functional interface of a Lambda Expression
  22. Spring @ContextConfiguration how to put the right location for the xml
  23. Where should I put @Transactional annotation: at an interface definition or at an implementing class?
  24. Multiple annotations of the same type on one element?
  25. Accessing source code from Java Annotation Processor
  26. What is the default annotation processors discovery process?
  27. What is Persistence Context?
  28. BeanNotOfRequiredTypeException due to autowired fields
  29. When to use DiscriminatorValue annotation in hibernate
  30. JPA Map mapping

Leave a Comment