syntax for passing array to annotation

Question

A few days ago I was forced to use the following construction for my class declaration:

@Table(name="UserPattern",  uniqueConstraints={
   @UniqueConstraint(columnNames={"user_id", "patern_id"})
})

I was very surprised by this syntax.

Usually I thought that if I should to pass array to annotation O I should write the following:

declared_inside_annotation_name={value1,value2...}

but in this case it looks like the following:

uniqueConstraints={
                    @UniqueConstraint(columnNames={"user_id", "patern_id"})
                  }

@Table annotation declaration:

@Target(TYPE)
@Retention(RUNTIME)
public @interface Table {

    String name() default "";


    String catalog() default "";


    String schema() default "";


    UniqueConstraint[] uniqueConstraints() default { };


    Index[] indexes() default {};
}

please clarify this syntax.

Could you point a difference between your expected notation of declared_inside_annotation_name={value1,value2...} and actual uniqueConstraints={single_value}? — Oleg Estekhin
– Oleg Estekhin, Commented Jul 15, 2014 at 9:38
instead of value1,value2 I see @UniqueConstraint(columnNames={value1,value2}) — gstackoverflow
– gstackoverflow, Commented Jul 15, 2014 at 10:35
You confuse the @Table.uniqueConstraints, which is an array of @UniqueConstraints and contains a single item, with the value @UniqueConstraint.columnNames, which belongs to another object and is an array of strings and contains two items. — Oleg Estekhin
– Oleg Estekhin, Commented Jul 15, 2014 at 10:46

Jack · Accepted Answer · 2014-07-15 09:54:41Z

1

There is actually not a conflict between your expected syntax from your declared_inside_annotation_name example and the syntax from the @Table annotation. The type of elements for an array property of an annotation does not necessarily have to be a string (which might be what you have expected). It may actually be another annotation.

This is the case with the uniqueConstraints property of the @Table annotation. If you check the declaration of the UniqueConstraint class, you see that it is an annotation itself. When writing it down, you use the usual @AnnotationTypeName notation.

answered Jul 15, 2014 at 9:54

Jack

3,0696 gold badges37 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

gstackoverflow Over a year ago

Thus @UniqueConstraint(columnNames={"user_id", "patern_id"}) one array element ?

Collectives™ on Stack Overflow

syntax for passing array to annotation

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related