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/*
* Copyright 2006-2010 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* 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 com.amazon.carbonado;
import java.lang.annotation.*;
/**
* Designates a {@link Storable} property as being the authoritative version
* number for the entire Storable instance. Only one property can have this
* designation.
*
* <p>Philosophically, a version property can be considered part of the
* identity of the storable. Unless the version is {@link Derived}, the
* repository is responsible for establishing the version on insert, and for
* auto-incrementing it on update. Under no circumstances should a normal
* version property be incremented manually; this can result in a false {@link
* OptimisticLockException}, or worse may allow the persistent record to become
* corrupted.
*
* <p>When updating a storable which has a normal version property, a value for
* the version must be specified along with its primary key. Otherwise, an
* {@link IllegalStateException} is thrown when calling update. If the update
* operation detects that the specified version doesn't exactly match the
* version of the existing persisted storable, an {@link
* OptimisticLockException} is thrown. For {@link Derived} versions, an {@link
* OptimisticLockException} is thrown only if the update detects that the new
* version hasn't incremented.
*
* <p>The actual type of the version property can be anything, but some
* repositories might only support integers. For maximum portability, version
* properties should be a regular 32-bit int.
*
* <p>Example:<pre>
* public interface UserInfo extends Storable {
* <b>@Version</b>
* int getRecordVersionNumber();
* void setRecordVersionNumber(int version);
*
* ...
* }
* </pre>
*
* @author Brian S O'Neill
* @author Don Schneider
* @see OptimisticLockException
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Version {
}
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