Entity store

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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