com.redhat.rhn.common.hibernate

Class ForceRecreationListType

java.lang.Object

com.redhat.rhn.common.hibernate.ForceRecreationListType

All Implemented Interfaces:

org.hibernate.usertype.UserCollectionType

public class ForceRecreationListType
extends java.lang.Object
implements org.hibernate.usertype.UserCollectionType

This is special user collection type that should be used when one wants to force the recreation of a list on a Many-Many mapping table. The example case where we are using this

Domain Model -> Many Servers (s) - Many Config Channels(cc) rhnServer (s) 1 <-* rhnServerConfigChannel (scc)* -> 1 rhnConfigChannel(cc) s -> (id), scc ->(server_id, config_channel_id, position ), cc->(id) here we are representing Server as holding a list of config channels that is indexed according to the value of scc.position. Now lets say we subscribed and unsubscribed channels from the Server... When saving server, with hibernates default mechanism, the links between the Server & ConfigChannels are not deleted and remapped from scratch. Instead an "optimization" is done using updates. For eg, if SCC read -> (sid, ccid, position) ->{(2,1,0),(2,2,1),(2,3,2)} And we remove the link for CCID = 1 to end up with ->{(2,2,1),(2,3,2)} Hibernate achieves this in the following order a) remove(2,3,2) ,b) moves (2,1,0)-> (2,2,0), c) move (2,2,1) -> (2,3,1) Problem here is since (sid, ccid) combination must be unique step b fails (since 2,2,1 still exists).. So we have to force hibernate to do the following a) remove (2,*,*) b) insert(2,2,0) and c)insert(2,3,1) This list type will help us achieve that.

When you use a list in hbm.xml , to use this collection you must specify <list name="...." collection-type="com.redhat.rhn.common.hibernate.ForceRecreationListType">

Note in the above example if (sid, ccid, position) combination as a whole was unique we wouldn't have had to deal with this...... but positions can be null twice for the same server, so we cannot enforce that constraint.. ForceRecreationListType

Constructor Summary

Constructors

Constructor and Description
ForceRecreationListType()

Method Summary

Modifier and Type	Method and Description
boolean	contains(java.lang.Object collection, java.lang.Object entity)
java.util.Iterator	getElementsIterator(java.lang.Object collection)
java.lang.Object	indexOf(java.lang.Object collection, java.lang.Object entity)
java.lang.Object	instantiate() Returns an ArrayList.
java.lang.Object	instantiate(int anticipatedSize) Instantiates an empty list.
org.hibernate.collection.PersistentCollection	instantiate(org.hibernate.engine.SessionImplementor session, org.hibernate.persister.collection.CollectionPersister persister)
java.lang.Object	replaceElements(java.lang.Object original, java.lang.Object target, org.hibernate.persister.collection.CollectionPersister persister, java.lang.Object owner, java.util.Map copyCache, org.hibernate.engine.SessionImplementor session)
org.hibernate.collection.PersistentCollection	wrap(org.hibernate.engine.SessionImplementor session, java.lang.Object collection)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ForceRecreationListType

public ForceRecreationListType()

Method Detail

instantiate

public org.hibernate.collection.PersistentCollection instantiate(org.hibernate.engine.SessionImplementor session,
                                                                 org.hibernate.persister.collection.CollectionPersister persister)
                                                          throws org.hibernate.HibernateException

Specified by:

instantiate in interface org.hibernate.usertype.UserCollectionType

Throws:

org.hibernate.HibernateException

wrap

public org.hibernate.collection.PersistentCollection wrap(org.hibernate.engine.SessionImplementor session,
                                                          java.lang.Object collection)

Specified by:

wrap in interface org.hibernate.usertype.UserCollectionType

getElementsIterator

public java.util.Iterator getElementsIterator(java.lang.Object collection)

Specified by:

getElementsIterator in interface org.hibernate.usertype.UserCollectionType

contains

public boolean contains(java.lang.Object collection,
                        java.lang.Object entity)

Specified by:

contains in interface org.hibernate.usertype.UserCollectionType

indexOf

public java.lang.Object indexOf(java.lang.Object collection,
                                java.lang.Object entity)

Specified by:

indexOf in interface org.hibernate.usertype.UserCollectionType

replaceElements

public java.lang.Object replaceElements(java.lang.Object original,
                                        java.lang.Object target,
                                        org.hibernate.persister.collection.CollectionPersister persister,
                                        java.lang.Object owner,
                                        java.util.Map copyCache,
                                        org.hibernate.engine.SessionImplementor session)
                                 throws org.hibernate.HibernateException

Specified by:

replaceElements in interface org.hibernate.usertype.UserCollectionType

Throws:

org.hibernate.HibernateException

instantiate

public java.lang.Object instantiate(int anticipatedSize)

Instantiates an empty list. This method will be useful when hibernate 3.2 is added.

Specified by:

instantiate in interface org.hibernate.usertype.UserCollectionType

Parameters:

anticipatedSize - sample size

Returns:

an empty list.

instantiate

public java.lang.Object instantiate()

Returns an ArrayList. Not sure what the heck this is here for. TODO: WHAT IS THIS FOR? 2007-11-8 jesusr

Returns:

ArrayList as an Object.