Extending @interface

Question

hi, first time posting...
I'm more of a hobbyist java programmer, so i can jump in to 1.5 faster than my friends who have to continue to use 1.3 or whatever because of what their company uses. the only downside to this is that I don't have anyone to ask! ok, so here goes
I was seeing if I could write some kind of Annotation, and then have another Annotation that extends it, inheriting its super's properties, etc, adding others, you know the deal. I have seen no documentation on this, but here's some code that I wrote that compiles (it's a lot like what Hibernate or OJB would do, but i was just testing so no code critique unless it's for Annotations :) )
//field.java
import java.lang.annotation.*;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface field {
     String columnName();
     Class type();
}i used lowercase but eventually when i really start writing stuff, I'll fix it (and rename it to Column or something). Anyway, then I tried to write a "primary key" annotation, which is a field, so naturally, i wanted to extend from field
//primaryKey.java
import java.lang.annotation.*;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface primaryKey extends field {
     boolean autoIncrement();
}but i get "primaryKey.java:5: extends not allowed for @interfaces"
so i try "extends @field" out of desperation, but that's a syntax error. next i try
public interface primaryKey extends fieldbut since the @retention and @target annotations are there, this doesn't compile either. i'm lost! can you not derive an annotation from another? my last option, which works, is to include "field" as a parameter for "@primaryKey"
import java.lang.annotation.*;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface primaryKey {
     field column();
     boolean autoIncrement();
}which would be used like so
@primaryKey(column=@field(columnName="id",type=java.lang.Integer.class),autoIncrement=true)
          public Integer id;any ideas or anyone just up for talking about this? i love talking java :-D

Answer 1

I'm going to guess that the way they were designed to be used is like this
define the @field Annotation and the @primaryKey annotation, then a field "id" has both Annotations on it, like so
        @field(columnName="id",type=java.lang.Integer.class)
     @primaryKey(autoIncrement=true)
          public Integer id;anybody? actually, that seems fine.