Re: Entity store

Hi Karl,

Neat, thanks for sharing.

Is the idea that you then use EntityStore as the root of your prevalent
system?

Cheers,
Justin


On Wed, Jul 14, 2010 at 10:38 AM, Karl Wettin <[email protected]> wrote:

> I've tried to factor out this entity object management I wrote for a
> project of mine that use Prevayler.
>
> http://github.com/karlwettin/kodapan-entity-store
>
> This is basically a thick layer around the two follwoing classes:
>
> /** All identifiable objects stored in a primary index must implement
> this class */
> interface EntityObject {
>   String getId();
> }
>
> class EntityStore {
>   /** One primary index per class and superclass assignable from
> EntityObject.
>       Makes it possible to iterate all instances of any entity class.
>       All entity objects are thus available as key EntityObject.class
> */
>   Map<Class<? extends EntityObject>, Map<String, EntityObject>>
> primaryIndices;
>
>   Map<String, Map<Object, Set<EntityObject>>> secondaryIndices;
> }
>
>
> Caveat emptor:
> * I ended up rewriting this API from scratch. Even though there are
> test cases for most of the stuff I have not yet been running this in a
> live environment so I'm sure there are bugs lurking in the darkness.
> * Forced string identity. (This might change to a byte[].)
> * Identities must be unique within the application, eg a UUID. (Comes
> with DeterministicUIDHandler)
> * Identities must be set before putting an entity to the store.
> * Secondary indices will not be updated unless you re-put the entity
> in the store or rebuild the secondary index.
>
>
> There is virtually no documentation but hopefully the API is simple
> enough:
>
> class EntityStore {
>   EntityObject put(EntityObject entity);
>   EntityObject get(String id);
>   boolean remove(String id);
>   PrimaryIndex<EntityType> getPrimaryIndex(Class<EntityType>
> entityType);
>   SecondaryIndex getSecondaryIndex(String name);
>   boolean registerSecondaryIndex(String name, SecondaryIndex
> secondaryIndex);
> }
>
> class PrimaryIndex<EntityType extends EntityObject> {
>   EntityType put(EntityType entity);
>   EntityType get(String id);
>   boolean remove(String id);
>   Map<String, EntityType> getEntitiesById();
> }
>
> abstract class SecondaryIndex<EntityType extends EntityObject> {
>   /** There are simple reflection based implementations */
>   abstract Object keyFactory(EntityType entity);
>   void put(EntityType entity);
>   boolean remove(EntityType entity);
>   EntityType get(Object... parameters);
>   Set<EntityType> list(Object... parameters);
> }
>
>
> http://github.com/karlwettin/kodapan-entity-store/blob/master/src/test/java/se/kodapan/index/TestEntityStore.java
>
> The test domain model can be viewed as UML class diagram here:
>
>
> http://github.com/karlwettin/kodapan-entity-store/raw/master/src/test/java/se/kodapan/index/domain/doc-files/classdiagram.pdf
>
> Beans can optionally be augmented with UML class diagram syntax
> annotations @BinaryAssociationEnd and @BinarAssociationClassEnd on
> fields, getters or setters to have the entity store automatically
> decouple instance from other ends and remove composite parts when the
> instance is removed. Compare with relational annotations for
> casacading, many to one and what not, but using OO syntax. Decoupling
> qualified binary associations (Maps) has not yet been implemented.
>
> I'm new to git, just noticed I've managed to push some old CVS and SVN
> directories to the repo so there might be other problems related to
> that too, sorry.
>
> I hope you find this a useful package but any comments or reports are
> most welcome!
>
>
> This depends on my common package <
> http://github.com/karlwettin/kodapan-common
>  > for annotations, reflection and collections. mvn install. I think
> some of you might question the SerializableBean class and want to
> remove it. It's work in progress for a more refactor friendly java
> serialization.
>
>
>
>
>        karl
>
>
>
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