org.eclipse.persistence.annotations.FetchAttribute Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of eclipselink Show documentation

EclipseLink build based upon Git transaction f2b9fc5

There is a newer version: 5.0.0-B03

/*
 * Copyright (c) 2011, 2018 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 v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// 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.RetentionPolicy.RUNTIME;

/**
 * A fetch attribute is specified within a fetch group and is used as 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.
 *
 * @author Guy Pelletier
 * @since EclipseLink 2.1
 */
@Target({})
@Retention(RUNTIME)
public @interface FetchAttribute {
    /**
     * (Required) The fetch attribute name.
     */
    String name();
}