Re: Entity store

15 jul 2010 kl. 06.47 skrev Justin T. Sampson:

> Hi Karl,
>
> Neat, thanks for sharing.
>
> Is the idea that you then use EntityStore as the root of your  
> prevalent system?

Right. You might want to subclass EntityStore or aggregate it from  
your own root in order to fit other things in there too. If you use  
java serialization I recommend non subclassing for your future  
refactoring needs.


	karl

>
> 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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