hi thomas,
thanks for clarification.
jakob
----- Original Message -----
From: "Thomas Mahler" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Monday, September 09, 2002 9:39 PM
Subject: Re: RelationshipHelper
> Hi Jakob,
>
> This helper is meant for situations where reference- and
> collection-descriptors are set to auto-retrieve="false".
> And the user wants to load the references by an explicit API call.
>
> We have all necessary stuff in PBImpl. Thus I'm planning to simply
> expose two new methods in the PB interface:
>
> retrieveAllReferences(Object instance)
> retrieveReference(Object instance, String referenceAttribute)
>
> cheers,
> Thomas
>
>
> Jakob Braeuchi wrote:
> > hi,
> >
> > i have to admit i haven't always followed this thread so please forgive
my
> > ignorance.
> > what's the purpose of the relationship helper ?
> > could it be integrated into ojb ?
> >
> > jakob
> >
> > ----- Original Message -----
> > From: "Charles Anthony" <[EMAIL PROTECTED]>
> > To: "'OJB Users List'" <[EMAIL PROTECTED]>
> > Sent: Monday, September 09, 2002 10:45 AM
> > Subject: RE: Anyone up for a "challange" ? :)
> >
> >
> >
> >>>Willingly to share the code - just to see it ? :)
> >>>
> >>>/max
> >>
> >>Voila!
> >>
> >>My RelationshipHelper delegates to a more complex object, the
appropriate
> >>sections of which are detailed below.
> >>
> >>Cheers,
> >>
> >>Charles.
> >>
> >> /**
> >> * If the relationship specified is not null, load the the named
> >> * relationship
> >> * @param o instance of an object
> >> * @param relationshipName the name of the relationship to load
> >> */
> >> public void loadRelationship(Object o, String relationshipName) {
> >> PersistenceBroker broker =
> >>PersistenceBrokerFactory.defaultPersistenceBroker();
> >>
> >> ClassDescriptor cld = broker.getClassDescriptor(o.getClass());
> >> ObjectReferenceDescriptor rd =
> >>cld.getObjectReferenceDescriptorByName(relationshipName);
> >> if (rd == null) {
> >> rd = cld.getCollectionDescriptorByName(relationshipName);
> >> }
> >>
> >> if (rd == null) {
> >> Log.error(this, "loadRelationship - couldn't find
relationship
> >>'" + relationshipName + "'");
> >> } else {
> >> PersistentField persistentField = rd.getPersistentField();
> >> Object currentValue = persistentField.get(o);
> >> if (currentValue == null) {
> >> if (rd instanceof CollectionDescriptor) {
> >> persistentField.set(o,
> >
> > getCollectionRelationship(broker,
> >
> >>o, relationshipName));
> >> } else {
> >> persistentField.set(o, getReferencedObject(broker,
o,
> >>relationshipName));
> >> }
> >> } else {
> >> Log.debug(this, "loadRelationship - relationship '" +
> >>relationshipName + "' already loaded on " + o);
> >> }
> >> }
> >> broker.close();
> >> }
> >>
> >>
> >> /**
> >> * Get Foreign key query for 1:n collection, by name
> >> *
> >> * Largely copied from
> >>org.apache.ojb.broker.singlevm.PersitenceBrokerImpl
> >> *
> >> * @return org.apache.ojb.broker.query.Query
> >> * @param obj
> >> * @param collectionName name of the collection to build the query
for
> >> */
> >> private Query getForeignKeyQuery(PersistenceBroker broker, Object
obj,
> >>String collectionName) {
> >> ClassDescriptor cld = broker.getClassDescriptor(obj.getClass());
> >> CollectionDescriptor cod =
> >>cld.getCollectionDescriptorByName(collectionName);
> >> ClassDescriptor refCld =
> >>broker.getClassDescriptor(cod.getItemClass());
> >>
> >> Object[] values = cld.getKeyValues(obj);
> >> FieldDescriptor[] fields =
> >>cod.getForeignKeyFieldDescriptors(refCld);
> >>
> >> Criteria criteria = new Criteria();
> >> for (int i = 0; i < fields.length; i++) {
> >> FieldDescriptor fld = (FieldDescriptor) fields[i];
> >> criteria.addEqualTo(fld.getAttributeName(), values[i]);
> >> }
> >>
> >> if (cod.getOrderBy() != null) {
> >> criteria.addOrderBy(cod.getOrderBy(), cod.isAscending());
> >> }
> >>
> >> Query query = QueryFactory.newQuery(refCld.getClassOfObject(),
> >>criteria, true);
> >>
> >> return query;
> >> }
> >>
> >> private Collection getCollectionRelationship(PersistenceBroker
broker,
> >>Object o, String collectionName) {
> >> ClassDescriptor cld = broker.getClassDescriptor(o.getClass());
> >> CollectionDescriptor cod =
> >>cld.getCollectionDescriptorByName(collectionName);
> >> Class collectionClass = cod.getCollectionClass();
> >> Collection results = null;
> >>
> >> Query fkQuery =
> >>getForeignKeyQuery(PersistenceBrokerFactory.defaultPersistenceBroker(),
o,
> >>collectionName);
> >> if (collectionClass == null) {
> >> results = broker.getCollectionByQuery(fkQuery);
> >> } else {
> >> results = (Collection)
> >>broker.getCollectionByQuery(collectionClass, fkQuery);
> >> }
> >> return results;
> >> }
> >>
> >> /**
> >> * Largely copied from
> >>org.apache.ojb.broker.singlevm.PersitenceBrokerImpl
> >> * @param obj
> >> * @param referenceName
> >> * @return
> >> */
> >> private Object getReferencedObject(PersistenceBroker broker, Object
> >
> > obj,
> >
> >>String referenceName) {
> >> ClassDescriptor cd = broker.getClassDescriptor(obj.getClass());
> >> ObjectReferenceDescriptor rds =
> >>cd.getObjectReferenceDescriptorByName(referenceName);
> >> Class referencedClass = rds.getItemClass();
> >> // ensure that top-level extents are used for Identities
> >>
> >> referencedClass =
> >>broker.getDescriptorRepository().getExtentClass(referencedClass);
> >>
> >> Object[] pkVals = rds.getForeignKeyValues(obj, cd);
> >>
> >> boolean allPkNull = true;
> >>
> >> // BRJ : check if we have non null pk values
> >> for (int i = 0; i < pkVals.length; i++) {
> >> if (pkVals[i] != null) {
> >> allPkNull = false;
> >> break;
> >> }
> >> }
> >>
> >> // BRJ : if all pk values are null there's no referenced object
> >> if (allPkNull) {
> >> return null;
> >> } else {
> >> Identity id = new Identity(referencedClass, pkVals);
> >> return broker.getObjectByIdentity(id);
> >> }
> >> }
> >>
> >>
> >>
> >>
> >>
> >>
> >>>-----Original Message-----
> >>>From: Max Rydahl Andersen [mailto:[EMAIL PROTECTED]]
> >>>Sent: 09 September 2002 09:35
> >>>To: OJB Users List
> >>>Subject: Re: Anyone up for a "challange" ? :)
> >>>
> >>>
> >>>Willingly to share the code - just to see it ? :)
> >>>
> >>>/max
> >>>
> >>>----- Original Message -----
> >>>From: "Charles Anthony" <[EMAIL PROTECTED]>
> >>>To: "'OJB Users List'" <[EMAIL PROTECTED]>
> >>>Sent: Monday, September 09, 2002 9:31 AM
> >>>Subject: RE: Anyone up for a "challange" ? :)
> >>>
> >>>
> >>>
> >>>>[snippety-snip]
> >>>>
> >>>>>crystal clear! This relationship helper is something I have thought
> >>>>>about in the last week. As all needed functionality is already
> >>>>>implemented in the PersistenceBroker it will be pretty easy
> >>>>
> >>>to expose
> >>>
> >>>>>such a feature in the public API.
> >>>>>I will put this feature on my personal todo list.
> >>>>
> >>>>Cool; spookily, I have a RelationshipHelper class, that has a
> >>>>lazilyLoadRelationship(Object o, String relationshipName),
> >>>
> >>>which basically
> >>>
> >>>>delegates clones of the appropriate methods on the PB. It'd
> >>>
> >>>be good to
> >>>kick
> >>>
> >>>>out the cut-n-paste code re-use !
> >>>>
> >>>>Chers,
> >>>>
> >>>>Charles.
> >>>>
> >>>>
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