net.sf.staccatocommons.restrictions.value.Value Maven / Gradle / Ivy
/**
* Copyright (c) 2011, The Staccato-Commons Team
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*/
package net.sf.staccatocommons.restrictions.value;
import java.io.Serializable;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Date;
import net.sf.staccatocommons.restrictions.Restriction;
/**
*
* {@link Value} annotation describes objects whose identity is not important,
* but that are completely described by its state instead, like {@link String}s,
* {@link Number}s and {@link Date}s.
*
* More formally, classes marked as {@link Value} must grant that it is possible
* to have two instances such that a != b && a.equals(b)
*
*
* Classes annotated this way grant that all their instances observe the
* following {@link Value} protocol
*
* - Implement equality so that it is not based in identity, but in its
* internal state instead. Values must override {@link #equals(Object)}
* - Implement hashCode to be consistent with equals, in order to be compliant
* with general {@link Object#hashCode()} contract
* - {@link Value}s implement {@link Object#toString()} in order to provide a
* descriptive representation of the object state
* - Are {@link Serializable}
*
*
* Although {@link Value} objects are usually immutable, this annotation does
* not make any assumption about it, as it only imposes restrictions regarding
* identity. Mutability aspect is covered by other annotations, like
* {@link Immutable}, {@link Unmodifiable} and the rest of the annotations
* defined in this package
*
*
* @see Immutable
* @see Unmodifiable
* @see Restriction
* @author flbulgarelli
*/
@Documented
@Inherited
@Restriction
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.TYPE)
public @interface Value {}