de.ipcon.db.castor

Class CastorPersistenceQueryResults

java.lang.Object

de.ipcon.db.castor.CastorPersistenceQueryResults

All Implemented Interfaces:

de.ipcon.db.core.QueryResultsI, java.io.Closeable, java.lang.AutoCloseable, java.util.Iterator

public class CastorPersistenceQueryResults
extends java.lang.Object
implements de.ipcon.db.core.QueryResultsI

This is the central query result implementation for the MyTISM framework utilizing the Castor JDO provider.

This class acts as a bridge between the native PersistenceHandlerI (Castor) and the high-level QueryResultsI interface. It supports both legacy SQL calls and modern, compiled OQL queries.

Key Features:

• Server-side Filtering: Integrates with the OQL compiler to apply Predicate filtering during iteration, minimizing the number of Business Objects (BOs) that reach the application layer.
• Memory Optimization: Automatically "slims" (untangles) unmatching or previously processed BOs in read-only mode to reduce memory pressure on the Garbage Collector.
• Prefetching: Supports eager loading of relation paths via prefetchPaths to avoid N+1 select issues in lazy-loading scenarios.

See Also:

OQLQuery, QueryResults

Constructor Summary

Constructors

Constructor and Description
CastorPersistenceQueryResults(CastorPersistenceHandler _ph, java.lang.String _query, java.lang.Object[] _parms, short _mode, java.lang.String[] _prefetchPaths) Constructs a new result set and immediately initiates the execution lifecycle.

Method Summary

Modifier and Type	Method and Description
void	cancel() Attempts to cancel the currently running database query if supported by the underlying driver and Castor implementation.
void	close() Closes the underlying result set and the query implementation.
java.lang.String	currentTag()
boolean	hasNext() Checks if a next record exists, taking the optional filterPredicate into account.
boolean	isClosed()
java.lang.Object	next() Returns the next result object.
void	remove() Modification via iterator is not supported in Castor OQL results.

Methods inherited from class java.lang.Object

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

Methods inherited from interface de.ipcon.db.core.QueryResultsI

spliterator, stream

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

CastorPersistenceQueryResults

public CastorPersistenceQueryResults(CastorPersistenceHandler _ph,
                                     java.lang.String _query,
                                     java.lang.Object[] _parms,
                                     short _mode,
                                     java.lang.String[] _prefetchPaths)

Constructs a new result set and immediately initiates the execution lifecycle.

Parameters:

_ph - The active CastorPersistenceHandler. Must not be finished or closed.

_query - The query string. If prefixed with "CALL SQL", it bypasses the OQL parser.

_parms - Input parameters. Null-safe; converted to empty array if null.

_mode - Persistence lock mode. Determines the isolation level of the fetched objects (e.g. READ_ONLY, SHARED, EXCLUSIVE).

_prefetchPaths - Attribute paths to be eagerly loaded.

Throws:

java.lang.IllegalStateException - If the provided PersistenceHandler is already in a 'finished' state.

PersistenceException - If OQL compilation or SQL execution fails.

Method Detail

close

public void close()

Closes the underlying result set and the query implementation.

In addition to resource cleanup, this method "slims" any currently held Business Objects to aid memory reclamation and notifies the handler of query performance metrics via ph.complainSlowQuery.

Specified by:

close in interface de.ipcon.db.core.QueryResultsI

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

isClosed

public boolean isClosed()

Specified by:

isClosed in interface de.ipcon.db.core.QueryResultsI

hasNext

public boolean hasNext()

Checks if a next record exists, taking the optional filterPredicate into account.

If a filter is present, this method will trigger a look-ahead fetch (prefetchNextFittingBO()) to determine if a matching record exists further down the stream.

Specified by:

hasNext in interface java.util.Iterator

Returns:

true if a call to next() will return an object.

Throws:

LockNotGrantedException - if a database lock prevents reading the next row.

PersistenceException - if there was a problem when accessing the underlying database.

next

public java.lang.Object next()

Returns the next result object.

If the persistence handler is not in a "saving" transaction, the previously returned BO is slimmed before returning the new one to keep the memory footprint minimal during large iterations.

Specified by:

next in interface java.util.Iterator

remove

public void remove()

Modification via iterator is not supported in Castor OQL results.

Specified by:

remove in interface java.util.Iterator

Throws:

java.lang.IllegalStateException - always.

currentTag

public java.lang.String currentTag()

Specified by:

currentTag in interface de.ipcon.db.core.QueryResultsI

cancel

public void cancel()

Attempts to cancel the currently running database query if supported by the underlying driver and Castor implementation.

Specified by:

cancel in interface de.ipcon.db.core.QueryResultsI