[jira] [Created] (JDO-764) Allow JDO annotations to be used in meta-annotations

["Andy Jefferson (JIRA)" <ji...@apache.org>]

Andy Jefferson created JDO-764:
----------------------------------

             Summary: Allow JDO annotations to be used in meta-annotations
                 Key: JDO-764
                 URL: https://issues.apache.org/jira/browse/JDO-764
             Project: JDO
          Issue Type: Improvement
          Components: api
            Reporter: Andy Jefferson


By default annotations are used directly in a persistable class. Java additionally allows annotations to be formed of other annotations. This is particularly useful where a user has a particular combination of annotations to set on a class/field/method and wants to simply annotate with an abbreviated form. For example, specifying attributes of an annotation

@PersistenceCapable(detachable="true", identityType="datastore", embeddedOnly="true")

or formed of multiple annotations

@PersistenceCapable(detachable="true")
@Extension(vendorName="datanucleus", key="multitenancy-column-name", value="TENANT")

These can be represented as meta-annotations like this

@Target(TYPE)
@Retention(RUNTIME)
@PersistenceCapable(detachable="true", identityType="datastore", embeddedOnly="true")
@interface @DatastoreIdPersistable
{
}

@Target(TYPE)
@Retention(RUNTIME)
@PersistenceCapable(detachable="true")
@Extension(vendorName="datanucleus", key="multitenancy-column-name", value="TENANT")
@interface @MultitenantPersistable
{
}

and the user can subsequently just annotate their persistable class as

@DatastoreIdPersistable
public class MyClass1 {...}


@MultitenantPersistable
public class MyClass2 {...}

The work required to support this in the JDO spec is simply to update the following annotations to add @Target({ElementType.ANNOTATION_TYPE})

The annotations requiring this are
@Element, @EmbeddedId, @Key, @NotPersistent, @Order, @Persistent, @Serialized, @Transactional, and @Value  (all other annotations already have @Target({ElementType.TYPE}) which already permits their usage in meta-annotations.

The same is proposed for JPA 2.2, see https://github.com/javaee/jpa-spec/issues/43



--
This message was sent by Atlassian JIRA
(v6.3.15#6346)