集的唯一约束 <String> 与Hibernate

Question

I'm having an Entity that contains a Set like the following:

@ElementCollection
Set<String> branches;

Now what Hibernate does, is creating a table project_branches (project_id | branches) and adding a unique constraint on branches . Is there any way to tell hibernate that the unique constraint should involve both, project_id and branches ?

I could not find an answer to this question, though I think I'm not the first with this problem... Thanks

Answer 1

This is dependent on the columns involved in the mapping.

There in one other configuration. Please consider adding an UniqueConstraint annotation at entity level eg below:

  @Table(name="project_branches",
    uniqueConstraints = {@UniqueConstraint(columnNames={"project_id", "branches"})}
  )

EDIT: Try using @CollectionTable annotation.

 @ElementCollection
 @CollectionTable(
    name="project_branches",
    joinColumns=@JoinColumn(name="branches"),
    uniqueConstraints = {@UniqueConstraint(columnNames={"project_id", "branches"})}
  )
  Set<String> branches;

Answer 2

Ok I found the solution: Entity fields support the Annotation @CollectionTable so I was able to solve it like this:

@ElementCollection(fetch = FetchType.EAGER)
@CollectionTable(name = "project_branches", uniqueConstraints = @UniqueConstraint(columnNames = {
        "project_id", "branches" }))
Set<String> branches = new HashSet<String>();