[OJB-developers] Bug in TransactionImpl.java (Null Pointer Exception) in 0.9

[Galvin H. <gk...@ya...>]

Encountered a null pointer exception that manifests
itself when attempting to update a m:n relationship
while using ODMG API - this is manifested in both
TransactionImpl and ObjectReferenceDescriptor.

In TransactionImpl: as it attempts to retrieve
getforeignKeyfielddescriptors() from
CollectionDescriptor(), the call can throw a null
pointer exception.

However, suppose that the CollectionDescriptor
(ObjectReferenceDescriptor descendant) has its
m_ForeignKeyFields not set or initialized. In fact,
m_ForeignKeyFields are initialized only if
addForeignKeyField() is called. Therefore, when
getForeignKeyFieldDescriptors() is called, this code
gets executed:

Vector v = getForeignKeyFields();
            
            /* WHAT HAPPENS IF v is NULL? NPE*/

            // 2. get FieldDescriptor for each index
from Class-descriptor
            Vector ret = new Vector();
            Iterator iter = v.iterator();
            while (iter.hasNext())
            {
                Integer index = (Integer) iter.next();
               
ret.add(mif.getFieldDescriptorByIndex(index.intValue()));
            }

TransactionImpl:

                ClassDescriptor itemCld =
this.getBroker().getClassDescriptor(cds.getItemClass());
                Object[] objPkValues =
cld.getKeyValues(newTxObject);

                /* BEGIN NULL POINTER EXCEPTION THREAT
*/
                FieldDescriptor[] itemFkFields =
cds.getForeignKeyFieldDescriptors(itemCld);
                /* END NULL POINTER EXCEPTION THREAT
*/
                while (colIterator.hasNext())
                {
                    Object item = colIterator.next();

                    // provide all items in collection
attributes
                    // with foreign key information
before locking them!
                    for (int j = 0; j <
itemFkFields.length; j++)
                    {
                        FieldDescriptor fld =
itemFkFields[j];
                       
fld.getPersistentField().set(item, objPkValues[j]);
                    }
                    lock(item, lockMode);
                }


Possible fix(es):  

1) Have the m_ForeignKeyFields initialized and
instantiated in the ObjectReferenceDescriptor()
constructor

2) Modify TransactionImpl to detect whether or not a
CollectionDescriptor has any fieldDescriptors at all -
if not just call lock(item, lockMode).  If so, provide
all items in collection attributes with foreign key
information before locking them.


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