/*
* Copyright 2013-2015 the original author or authors.
*
* 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 org.springframework.integration.support;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicLong;
import org.springframework.util.IdGenerator;
/**
* Alternative {@link IdGenerator} implementations.
*
* @author Andy Wilkinson
* @since 4.0
*
*/
public class IdGenerators {
/**
* UUID.randomUUID()
*
*/
public static class JdkIdGenerator implements IdGenerator {
@Override
public UUID generateId() {
return UUID.randomUUID();
}
}
/**
* Based on the two {@link AtomicLong}s, for {@code topBits} and {@code bottomBits},
* respectively.
* Begins with {0, 1}; incremented on each use.
* <p>
* Note: after each {@code 2^63} generations, a duplicate {@link UUID}
* can be returned in a multi-threaded environment, if a second thread sees the old topBits
* before it is incremented by the thread detecting the bottomBits roll over.
* The duplicate would be from around the previous rollover and
* the chance of such a value still being in the system is exceedingly small.
* If your system might be impacted by this situation, you should choose another {@link IdGenerator}.
* Also note that there is no persistence, so this generator starts at {0, 1} each time the system
* is initialized. Therefore, it is not suitable when persisting messages based on their ID; it should
* only be used when the absolute best performance is required and messages are not persisted.
*/
public static class SimpleIncrementingIdGenerator implements IdGenerator {
private final AtomicLong topBits = new AtomicLong();
private final AtomicLong bottomBits = new AtomicLong();
@Override
public UUID generateId() {
long bottomBits = this.bottomBits.incrementAndGet();
if (bottomBits == 0) {
return new UUID(this.topBits.incrementAndGet(), bottomBits);
}
else {
return new UUID(this.topBits.get(), bottomBits);
}
}
}
}