net.sf.mmm.util.bean.api.link

Interface Link<E extends EntityBean>

Type Parameters:

E - the generic type of the linked EntityBean.

All Known Implementing Classes:

AbstractLink, EntityBeanLink, IdLink

public interface Link<E extends EntityBean>

This is the interface for a link to an EntityBean. It acts as a reference that can be evaluated lazily. It will hold the primary key of the linked bean.

Since:

8.0.0

Author:

hohwille

See Also:

EntityBeanLink, IdLink

Method Summary

Modifier and Type	Method and Description
Id<E>	getId()
E	getTarget() This method resolves the linked EntityBean. ATTENTION: An Link can be evaluated lazily.
boolean	isResolved()

Method Detail

getId

Id<E> getId()

Returns:

the unique identifier of the linked bean. When creating new Beans a link may hold a transient EntityBean as target that has no ID assigned, yet. In such case this method will return null.

isResolved

boolean isResolved()

Returns:

true if the link target is already resolved, false otherwise (if getTarget() may trigger lazy loading and could also fail if called without an open transaction).

getTarget

E getTarget()

This method resolves the linked EntityBean.
ATTENTION:
An Link can be evaluated lazily. In such case the first call of this method will resolve the linked EntityBean from the database. That can be a relatively expensive operation and requires an open transaction. Use isResolved() to distinguish and prevent undesired link resolving.
Further, after serialization (e.g. mapping to JSON and back) maybe only the ID was transferred and this link can not be resolved. In that case this method may return null. Please note that id and target can not both be null. In case a link property is empty it will contain null instead of an empty Link so you can always properly distinguish the scenarios.

Returns:

the link target or null if the link can not be resolved.