/******************************************************************************* | |
* Copyright (c) 2011, 2013 Oracle and/or its affiliates. All rights reserved. | |
* This program and the accompanying materials are made available under the | |
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 | |
* which accompanies this distribution. | |
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html | |
* and the Eclipse Distribution License is available at | |
* http://www.eclipse.org/org/documents/edl-v10.php. | |
* | |
* Contributors: | |
* 01/19/2010-2.1 Guy Pelletier | |
* - 211322: Add fetch-group(s) support to the EclipseLink-ORM.XML Schema | |
******************************************************************************/ | |
package org.eclipse.persistence.annotations; | |
import java.lang.annotation.Retention; | |
import java.lang.annotation.Target; | |
import static java.lang.annotation.ElementType.TYPE; | |
import static java.lang.annotation.RetentionPolicy.RUNTIME; | |
/** | |
* A fetch group is a performance enhancement that allows a group of attributes | |
* of an object to be loaded on demand, which means that the data for an | |
* attribute might not loaded from the underlying data source until an explicit | |
* access call for the attribute first occurs. It avoids the wasteful practice | |
* of loading up all data of the object's attributes, in which the user is | |
* interested in only partial of them. | |
* | |
* A great deal of caution and careful system use case analysis should be use | |
* when using the fetch group feature, as the extra round-trip would well offset | |
* the gain from the deferred loading in many cases. | |
* | |
* EclipseLink fetch group support is twofold: the pre-defined fetch groups at | |
* the Entity or MappedSuperclass level; and dynamic (use case) fetch groups at | |
* the query level. | |
* | |
* Fetch groups can only be used when weaving is enabled or when individual | |
* classes that define them explicitly implement the | |
* org.eclipse.persistence.queries.FetchGroupTracker interface. | |
* | |
* @author Guy Pelletier | |
* @since EclipseLink 2.1 | |
*/ | |
@Target({TYPE}) | |
@Retention(RUNTIME) | |
public @interface FetchGroup { | |
/** | |
* (Required) The fetch group name. | |
*/ | |
String name(); | |
/** | |
* (Optional) Indicates whether all relationship attributes | |
* specified in the fetch group should be loaded. | |
*/ | |
boolean load() default false; | |
/** | |
* (Required) The list of attributes to fetch. | |
*/ | |
FetchAttribute[] attributes(); | |
} |