bitronix.tm.utils.UidGenerator Maven / Gradle / Ivy
/*
* Copyright (C) 2006-2013 Bitronix Software (http://www.bitronix.be)
*
* 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 bitronix.tm.utils;
import bitronix.tm.BitronixXid;
import bitronix.tm.TransactionManagerServices;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Helper that offers UID generation (GTRID, XID, sequences) needed by the transaction manager.
* Generated UIDs are at most 64 bytes long and are made of 3 subparts: the current time in milliseconds since
* Epoch, a JVM transient atomic sequence number and the configured bitronix.tm.serverId.
* The reliance on the system clock is critical to the uniqueness of the UID in the network so you have to make sure
* all servers of the network running this transaction manager have their clock reasonably in sync. An order of 1
* second synchronicity is generally fine.
*
* @author Ludovic Orban
*/
public class UidGenerator
{
private static final AtomicInteger sequenceGenerator = new AtomicInteger();
private UidGenerator()
{
//Static class
}
/**
* Generate a XID with the specified globalTransactionId.
*
* @param gtrid
* the GTRID to use to generate the Xid.
*
* @return the generated Xid.
*/
public static BitronixXid generateXid(Uid gtrid)
{
return new BitronixXid(gtrid, generateUid());
}
/**
* Generate a UID, globally unique. This method relies on the configured serverId for network uniqueness.
*
* @return the generated UID.
*/
public static Uid generateUid()
{
byte[] timestamp = Encoder.longToBytes(MonotonicClock.currentTimeMillis());
byte[] sequence = Encoder.intToBytes(sequenceGenerator.incrementAndGet());
byte[] serverId = TransactionManagerServices.getConfiguration()
.buildServerIdArray();
int uidLength = serverId.length + timestamp.length + sequence.length;
byte[] uidArray = new byte[uidLength];
System.arraycopy(serverId, 0, uidArray, 0, serverId.length);
System.arraycopy(timestamp, 0, uidArray, serverId.length, timestamp.length);
System.arraycopy(sequence, 0, uidArray, serverId.length + timestamp.length, sequence.length);
return new Uid(uidArray);
}
}