>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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