net.sf.mmm.util.entity.api

Interface GenericEntity<ID>

Type Parameters:

ID - is the type of the primary key.

All Superinterfaces:

AttributeReadId<ID>, Entity, Serializable

All Known Subinterfaces:

MutableGenericEntity<ID>, MutableRevisionedEntity<ID>, PersistenceEntity<ID>, RevisionedEntity<ID>

All Known Implementing Classes:

AbstractGenericEntity, AbstractRevisionedEntity, EntityTo

public interface GenericEntity<ID>
extends AttributeReadId<ID>, Entity

This is the interface for a (persistent) entity, which is an object that is potentially stored in a persistent store (typically a database and via JPA). Every non-abstract implementation of this interface is simply called an entity or business-object. It is supposed to be a simple java-bean or in words a Pojo.
This interface makes the following assumptions:

• A GenericEntity is identified by a primary key.
• A GenericEntity has a modification counter for optimistic locking (even though not strictly required - you could statically return 0).

ATTENTION:
An instance of this interface can be one of the following:

• a PersistenceEntity
  
• a transfer-object
  

In order to distinguish the above cases an application has an architecture that organizes the code in technical layers (see multilayered architecture) and business oriented slices (business components). Therefore within the persistence layer instances should always be persistence entities (independent from their actual state such as managed). On the other hand in the higher layers instances always need to be TransferObjects. Our recommendation is to convert persistent entities into entity transfer-objects when exposing functionality in the API of the logic layer.

Since:

3.0.0

Author:

Joerg Hohwiller (hohwille at users.sourceforge.net)

See Also:

Entity

Method Summary

Modifier and Type	Method and Description
ID	getId() This method gets the unique identifier (primary key) of this entity.
int	getModificationCounter() This method gets the current modification-counter of this entity.

Method Detail

getId

ID getId()

This method gets the unique identifier (primary key) of this entity. While this method is initially defined in a generic way, it is strongly recommended to use Long as datatype for IDs.
Even if you want to have a String-based business-oriented identifier it is best practice to use a Long as primary key and add the business identifier as additional field (with a unique constraint). This way references to the entity will be a lot more compact and improve your performance in JOINs or the like. However, there may be reasons to use other datatypes for the ID. In any case the unique ID should be an immutable java-object that can be rebuild from its string-representation.
Please note that if your ID has a specific syntax, semantic, formatting rules, etc. you should create a custom Datatype for it. If it can easily be mapped to a Long value you can still use Long here and provide a transient getter method that returns the your custom Datatype from the Long.

Specified by:

getId in interface AttributeReadId<ID>

Returns:

the ID of this entity. It may be null if the object is new and no ID has manually been assigned.

getModificationCounter

int getModificationCounter()

This method gets the current modification-counter of this entity. Whenever the object gets modified and saved, this counter will be increased. The initial value after construction is 0.
If this feature is NOT supported for some reason, this method should always return 0.

Returns:

the current modification-counter.

See Also:

Version