db-jdo-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Andy Jefferson <a...@jpox.org>
Subject Re: Thoughts about JDO 2.1 Annotation
Date Tue, 16 Jan 2007 07:12:14 GMT
Hi Ilan,

always good to see some ideas on improving the annotations

> 1. Using simple annotations instead of complex attributes
> For instance:
>     @PrimaryKey
> instead of:
>     @Field(primaryKey=true)
> (or simply @Id as in JPA).

OK, but the other point of view is where we have a field that needs several 
attributes setting (e.g NullValue, Dependent, PrimaryKey, etc) we end up with 
a long list of annotations against it. In that case a single annotation is 
cleaner IMHO. But yes I agree in the case of say one or two attributes to be 
added that it would add more flexibility and be simpler.

It doesn't have to be a question of whether we have the attributes in Field OR 
have things like PrimaryKey. We could allow both.

> Also, maybe @Index should be defined without unique option, by:
>     public @interface Indexed { boolean value() default true; }
> or maybe even by:
>     public @interface Unique {}
> and simply used with:
>     @Indexed
> Do we really need so many different methods to define a unique index?

Some ideas :-
1. I'd remove "indexed" attribute from @Field since we can have @Index 
specified on the field.
2. I'd remove "unique" attribute from @Field since we can have @Unique 
specified on the field.
3. I'd change @Index to make "name" and "table" default to "" (so we can then 
just specify @Index against a field (this then means the same as 
"indexed=true")
4. I'd change @Unique to make "name" and "table" default to "" (so we can then 
just specify @Unique against a field (this then means the same as 
"unique=true")

@Index is defined with a "unique" option for RDBMS convenience IIRC.


> 2. Discarding @Array, @Collection and @Map
> It seems logical to move the attributes of @Array, @Collection and @Map to
> @Element, @Key and @Value. The separation (whose origin is in the XML) is
> unclear to me.

Agreed. 
The separation in MetaData is JDO1 backwards compatibility (i.e the "element", 
"key", "value" didnt exist in JDO1 and the attributes of their types etc were 
already on the array, collection, map so were left there ... I think). 
Obviously with annotations we dont have to consider backwards compatibility.

> 3. Merging all annotations to one package
> Good separation seems to be very difficult. For instance - @Index, which is
> currently in orm has both columns and fields as attributes. Fields are not
> related to orm - just columns. If the separation remains, at least moving
> @Index, @Indices, @Unique, @Uniques, @Element, @Key and @Value that contain
> also non orm information should be pulled out to the main package.

No complaints from me. I had them together at the start and received a request 
to split them. As you say, what to include as "orm" and what not is not 
clear. ODBMS usually allow Index, Unique etc whereas these are in the ORM 
DTD.

If the issue here is discouraging users from putting "ORM" info as annotations 
then documentation (and annotation tools) is the way to do that.

> 4. Type attributes should be Class rather than String
> For instance, in Field:
>     Class fieldType();
> instead of:
>     String fieldType() default "";

I think that should be
Class fieldType() void.class;
because otherwise it becomes "required".

Similarly PersistenceCapable.objectIdClass

> 5. RecursionDepth
> Should be added somehow to the fields in @FetchGroup (and removed from
> @Field if unused).

I was originally intending on having Field[] as an attribute of FetchGroup. 
Since we only really need the field name and the recursion-depth there it 
would be nice to provide notation just for those. What this notation would be 
is not clear to me however.


-- 
Andy

Mime
View raw message