@UniqueConstraint annotation in Java
To ensure a field value is unique you can write
@Column(unique=true)String username;The @UniqueConstraint annotation is for annotating multiple unique keys at the table level, which is why you get an error when applying it to a field.
References (JPA TopLink):
You can use at class level with following syntax
@Entity@Table(uniqueConstraints={@UniqueConstraint(columnNames={"username"})})public class SomeEntity { @Column(name = "username") public String username;}
I'm currently using play framework too with hibernate and JPA 2.0 annotation and this model works without problems
@Entity@Table(uniqueConstraints={@UniqueConstraint(columnNames = {"id_1" , "id_2"})})public class class_name {@Id@GeneratedValuepublic Long id;@NotNullpublic Long id_1;@NotNullpublic Long id_2;}Hope it helped.