org.datanucleus.store.rdbms.query
Class ScrollableQueryResult

java.lang.Object
  java.util.AbstractCollection<E>
      java.util.AbstractList
          org.datanucleus.store.query.AbstractQueryResult
              org.datanucleus.store.rdbms.query.AbstractRDBMSQueryResult
                  org.datanucleus.store.rdbms.query.ScrollableQueryResult

All Implemented Interfaces:

Serializable, Iterable, Collection, List, org.datanucleus.store.query.QueryResult

public final class ScrollableQueryResult
extends AbstractRDBMSQueryResult
implements Serializable

Lazy collection results from a Query with the ResultSet scrollable. Supports the following query extensions (in addition to those supported by superclasses) :-

• datanucleus.query.resultCacheType Type of caching of result objects. Supports strong, weak, soft, none

If there is no transaction present, or if the FetchPlan is in "greedy" mode, and where caching is being used will load all results at startup. Otherwise results are only loaded when accessed.

See Also:

Serialized Form

Field Summary

protected Map<Integer,Object>

resultIds

Fields inherited from class org.datanucleus.store.rdbms.query.AbstractRDBMSQueryResult

rof, rs

Fields inherited from class org.datanucleus.store.query.AbstractQueryResult

closed, connectionListeners, loadResultsAtCommit, LOCALISER, query, resultSizeMethod, size

Fields inherited from class java.util.AbstractList

modCount

Constructor Summary

ScrollableQueryResult(org.datanucleus.store.query.Query query, org.datanucleus.store.query.ResultObjectFactory rof, ResultSet rs, Collection candidates)
Constructor of the result from a Query.

Method Summary

protected void	cacheQueryResults()
void	close() Method to close the results, making the results unusable thereafter.
protected void	closingConnection() Inform the query result that the connection is being closed so perform any operations now, or rest in peace.
boolean	equals(Object o) Equality operator for QueryResults.
Object	get(int index) Method to retrieve a particular element from the list.
protected Object	getObjectForIndex(int index) Accessor for the result object at an index.
protected int	getSizeUsingMethod() Method to get the size using the "resultSizeMethod".
Iterator	iterator() Accessor for an iterator for the results.
ListIterator	listIterator() Accessor for an iterator for the results.
protected void	loadObjects(int start, int maxNumber) Convenience method to load up rows starting at the specified position.
Object[]	toArray()
Object[]	toArray(Object[] a)
protected Object	writeReplace() Handle serialisation by returning a java.util.ArrayList of all of the results for this query after disconnecting the query which has the consequence of enforcing the load of all objects.

Methods inherited from class org.datanucleus.store.rdbms.query.AbstractRDBMSQueryResult

closeResults, disconnect, hashCode

Methods inherited from class org.datanucleus.store.query.AbstractQueryResult

add, add, addAll, addConnectionListener, assertIsOpen, clear, contains, containsAll, indexOf, isEmpty, isOpen, lastIndexOf, remove, set, size, subList

Methods inherited from class java.util.AbstractList

listIterator, removeRange

Methods inherited from class java.util.AbstractCollection

addAll, remove, removeAll, retainAll, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

addAll, remove, removeAll, retainAll

Methods inherited from interface java.util.List

addAll, remove, removeAll, retainAll

Field Detail

resultIds

protected Map<Integer,Object> resultIds

Constructor Detail

ScrollableQueryResult

public ScrollableQueryResult(org.datanucleus.store.query.Query query,
                             org.datanucleus.store.query.ResultObjectFactory rof,
                             ResultSet rs,
                             Collection candidates)

Constructor of the result from a Query.

Parameters:

query - The Query

rof - The factory to retrieve results from

rs - The ResultSet from the Query Statement

candidates - the Candidates collection. Pass this argument only when distinct = false

Method Detail

loadObjects

protected void loadObjects(int start,
                           int maxNumber)

Convenience method to load up rows starting at the specified position. Optionally takes a maximum number of rows to process.

Parameters:

start - Start row

maxNumber - Max number to process (-1 means no maximum)

getObjectForIndex

protected Object getObjectForIndex(int index)

Accessor for the result object at an index. If the object has already been processed will return that object, otherwise will retrieve the object using the factory.

Parameters:

index - The list index position

Returns:

The result object

close

public void close()

Method to close the results, making the results unusable thereafter.

Specified by:

close in interface org.datanucleus.store.query.QueryResult

Overrides:

close in class AbstractRDBMSQueryResult

closingConnection

protected void closingConnection()

Inform the query result that the connection is being closed so perform any operations now, or rest in peace.

Specified by:

closingConnection in class org.datanucleus.store.query.AbstractQueryResult

cacheQueryResults

protected void cacheQueryResults()

iterator

public Iterator iterator()

Accessor for an iterator for the results.

Specified by:

iterator in interface Iterable

Specified by:

iterator in interface Collection

Specified by:

iterator in interface List

Specified by:

iterator in class org.datanucleus.store.query.AbstractQueryResult

Returns:

The iterator

listIterator

public ListIterator listIterator()

Accessor for an iterator for the results.

Specified by:

listIterator in interface List

Specified by:

listIterator in class org.datanucleus.store.query.AbstractQueryResult

Returns:

The iterator

equals

public boolean equals(Object o)

Equality operator for QueryResults. Overrides the AbstractList implementation since that uses size() and iterator() and that would cause problems when closed.

Specified by:

equals in interface Collection

Specified by:

equals in interface List

Specified by:

equals in class org.datanucleus.store.query.AbstractQueryResult

Parameters:

o - The object to compare against

Returns:

Whether they are equal

get

public Object get(int index)

Method to retrieve a particular element from the list.

Specified by:

get in interface List

Specified by:

get in class org.datanucleus.store.query.AbstractQueryResult

Parameters:

index - The index of the element

Returns:

The element at index

getSizeUsingMethod

protected int getSizeUsingMethod()

Method to get the size using the "resultSizeMethod". This implementation supports "LAST" method. Override this in subclasses to implement other methods.

Overrides:

getSizeUsingMethod in class org.datanucleus.store.query.AbstractQueryResult

Returns:

The size

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection

Specified by:

toArray in interface List

Overrides:

toArray in class org.datanucleus.store.query.AbstractQueryResult

toArray

public Object[] toArray(Object[] a)

Specified by:

toArray in interface Collection

Specified by:

toArray in interface List

Overrides:

toArray in class org.datanucleus.store.query.AbstractQueryResult

writeReplace

protected Object writeReplace()
                       throws ObjectStreamException

Handle serialisation by returning a java.util.ArrayList of all of the results for this query after disconnecting the query which has the consequence of enforcing the load of all objects.

Returns:

The object to serialise

Throws:

ObjectStreamException