/*
* JEF - Copyright 2009-2010 Jiyi (mr.jiyi@gmail.com)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jef.database.annotation;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* JPA中只支持对实体的多表引用，EasyFrame中还支持对单个字段的跨表引用。
* 为此增加了FieldOfTargetEntity这个Annonation，用于描述字段引用自目标实体的某个属性。
*
* 字段引用都只用于查询操作，不能用于插入和更新操作
* <p>为什么要有这个功能？</p>
* 笔者在设计GeeQuery时，考虑到性能问题，很多时候不需要查询目标整个实体，只需要个别字段即可。
*
*
*
* @Date 2011-4-12
*/
@Target(FIELD)
@Retention(RUNTIME)
public @interface FieldOfTargetEntity {
/**
* @see FieldOfTargetEntity
* @return field name
*/
String value();
}