oracle.toplink.descriptors
Class FetchGroupManager

java.lang.Object
  oracle.toplink.descriptors.FetchGroupManager

All Implemented Interfaces:

java.lang.Cloneable

public class FetchGroupManager
extends java.lang.Object
implements java.lang.Cloneable

Purpose: The fetch group manager controls the named fetch groups defined at the descriptor level. TopLink supports multiple, overlapped fetch groups, optionally with one of them as the default fetch group.

The domain object must implement oracle.toplink.queryframework.FetchGroupTracker interface, in order to make use of the fetch group performance enhancement feature.

Please refer to FetchGroup class for the prons and cons of fetch group usage.

Since:

TopLink 10.1.3.

See Also:

FetchGroup, FetchGroupTracker

Constructor Summary

FetchGroupManager()
Constructor

Method Summary

void	addFetchGroup(FetchGroup group) Add a named fetch group to the descriptor
FetchGroup	getDefaultFetchGroup() Return the descriptor-level default fetch group.
ClassDescriptor	getDescriptor() Return the referenced descriptor.
FetchGroup	getFetchGroup(java.lang.String groupName) Return a pre-defined named fetch group.
java.util.Map	getFetchGroups() Return the fetch group map: keyed by the group name, valued by the fetch group object.
boolean	isAttributeFetched(java.lang.Object object, java.lang.String attributeName) Return true if the attribute of the object has already been fetched
void	setDefaultFetchGroup(FetchGroup newDefaultFetchGroup) Set the descriptor-level default fetch group.
void	setDescriptor(ClassDescriptor descriptor) Set the referenced descriptor.

Methods inherited from class java.lang.Object

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

Constructor Detail

FetchGroupManager

public FetchGroupManager()

Constructor

Method Detail

addFetchGroup

public void addFetchGroup(FetchGroup group)

Add a named fetch group to the descriptor

getFetchGroups

public java.util.Map getFetchGroups()

Return the fetch group map: keyed by the group name, valued by the fetch group object.

getDefaultFetchGroup

public FetchGroup getDefaultFetchGroup()

Return the descriptor-level default fetch group. All read object and read all queries would use the default fetch group if no fetch group is explicitly defined for the query, unless setShouldUseDefaultFetchGroup(false); is also called on the query. Default fetch group should be used carefully. It would be beneficial if most of the system queries are for the subset of the object, so un-needed attributes data would not have to be read, and the users do not have to setup every query for the given fetch group, as default one is always used. However, if queries on object are mostly use case specific and not systematic, using default fetch group could cause undesirable extra round-trip and performance degradation.

See Also:

ObjectLevelReadQuery.setShouldUseDefaultFetchGroup(boolean)

getFetchGroup

public FetchGroup getFetchGroup(java.lang.String groupName)

Return a pre-defined named fetch group.

setDefaultFetchGroup

public void setDefaultFetchGroup(FetchGroup newDefaultFetchGroup)

Set the descriptor-level default fetch group. All read object and read all queries would use the default fetch group if no fetch group is explicitly defined for the query, unless setShouldUseDefaultFetchGroup(false); is also called on the query. Default fetch group should be used carefully. It would be beneficial if most of the system queries are for the subset of the object, so un-needed attributes data would not have to be read, and the users do not have to setup every query for the given fetch group, as default one is always used. However, if queries on object are mostly use case specific and not systematic, using default fetch group could cause undesirable extra round-trip and performance degradation.

See Also:

ObjectLevelReadQuery.setShouldUseDefaultFetchGroup(boolean)

isAttributeFetched

public boolean isAttributeFetched(java.lang.Object object,
                                  java.lang.String attributeName)

Return true if the attribute of the object has already been fetched

getDescriptor

public ClassDescriptor getDescriptor()

Return the referenced descriptor.

setDescriptor

public void setDescriptor(ClassDescriptor descriptor)

Set the referenced descriptor.