@Table Annotation

[Joe Harry]

What does the catalogue refers to in the annotation definition for @Table?

[Joe Harry]

Also what does the @UniqueConstraint at a class level signify?

[Joe Harry]

With respect to the @UniqueConstraints, is it something like, we can collectively place this constraint at the Type?
Like @Table.UniqueConstraint(column1, column2)??

[Christophe Verré]

What does the catalogue refers to in the annotation definition for @Table?

This is related to databases. From EJB3 In Action, "you can think of a catalog as a "meta-schema" or a higher-level abstraction for organizing schemas. Often, a database will only have one common system catalog".

Also what does the @UniqueConstraint at a class level signify?

At a class level ? What do you mean by that ? @UniqueConstraint is used in the @Table annotation. From the API :
"This annotation is used to specify that a unique constraint is to be included in the generated DDL for a primary or secondary table."

    @Table(
        name="EMPLOYEE", 
        uniqueConstraints=
            @UniqueConstraint(columnNames={"EMP_ID", "EMP_NAME"})
    )