Unique constraints on members of embedded member in Hibernate

Question

Is it possible to define unique constraints on members of an embedded class in Hibernate?

I need to be sure that Nested::i1 and Nested::i2 are unique as a pair (the combination)

@Entity
@Table( uniqueConstrains = ???)
public class Widget {
   @Id
   private int id;

   @Embedded
   Nested nested;
}

@Embeddable
public class Nested {
    private int i1;
    private int i2;
}

Answer 1

It is possible by using:

@Entity
@Table(uniqueConstraints = { @UniqueConstraint(columnNames = {"i1", "i2"})})
public class Widget {

It would result in CREATE SQL (postgresql example)

create table Widget 
(  id int8 not null,
   i1 int8, 
   i2 int8 ,
   primary key (id),
   unique (i1, i2)
) 

Optionally - it would be probably more consise and readable when you add @AttributeOverride annotation specyfying in one file - column names for both attributes

@AttributeOverrides({
        @AttributeOverride(name = "i1", column = @Column(name = "i1")),
        @AttributeOverride(name = "i2", column = @Column(name = "i2"))
})
@Embedded
Nested nested;