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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