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Part of MOB-436: Cluster-wide Locking Service: Implement DB Changes and Service
- Unit test not checked in as it requires some schema change work that has been done manually - Moved activities DAO code and renamed data services to DAOs (as per iBatis and Wikipedia, etc) - DAO code should now go into org.alfresco.repo.domain... - DAO components are bean:xyzDAO and class:XyzDAO - Entity beans are XyzEntity, etc git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@13922 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261
This commit is contained in:
Derek Hulley
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/*
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* Copyright (C) 2005-2009 Alfresco Software Limited.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* As a special exception to the terms and conditions of version 2.0 of
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* the GPL, you may redistribute this Program in connection with Free/Libre
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* and Open Source Software ("FLOSS") applications as described in Alfresco's
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* FLOSS exception. You should have recieved a copy of the text describing
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* the FLOSS exception, and it is also available here:
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* http://www.alfresco.com/legal/licensing"
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*/
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package org.alfresco.repo.domain.locks;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.StringTokenizer;
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import org.alfresco.repo.domain.QNameDAO;
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import org.alfresco.service.namespace.QName;
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import org.alfresco.util.EqualsHelper;
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import org.springframework.dao.ConcurrencyFailureException;
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/**
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* Abstract implementation of the Locks DAO.
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*
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* @author Derek Hulley
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* @since 3.2
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*/
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public abstract class AbstractLockDAOImpl implements LockDAO
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{
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private QNameDAO qnameDAO;
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/**
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* @return Returns the DAO for namespace ID resolution
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*/
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protected QNameDAO getQNameDAO()
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{
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return qnameDAO;
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}
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/**
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* @param qnameDAO DAO for namespace ID resolution
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*/
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public void setQnameDAO(QNameDAO qnameDAO)
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{
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this.qnameDAO = qnameDAO;
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}
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public boolean getLock(QName lockQName, String lockApplicant, long timeToLive)
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{
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String qnameNamespaceUri = lockQName.getNamespaceURI();
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String qnameLocalName = lockQName.getLocalName();
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// Force lower case for case insensitivity
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if (!qnameLocalName.toLowerCase().equals(qnameLocalName))
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{
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lockQName = QName.createQName(qnameNamespaceUri, qnameLocalName.toLowerCase());
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qnameLocalName = lockQName.getLocalName();
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}
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// Force the lock applicant to lowercase
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lockApplicant = lockApplicant.toLowerCase();
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// Resolve the namespace
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Long qnameNamespaceId = qnameDAO.getOrCreateNamespace(qnameNamespaceUri).getFirst();
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// Get the lock resource for the exclusive lock.
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// All the locks that are created will need the exclusive case.
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LockResourceEntity exclusiveLockResource = getLockResource(qnameNamespaceId, qnameLocalName);
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if (exclusiveLockResource == null)
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{
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// Create it
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exclusiveLockResource = createLockResource(qnameNamespaceId, qnameLocalName);
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}
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Long requiredExclusiveLockResourceId = exclusiveLockResource.getId();
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// Split the lock name
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List<QName> lockQNames = splitLockQName(lockQName);
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List<Long> requiredLockResourceIds = new ArrayList<Long>(lockQNames.size());
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// Create the lock resources
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for (QName lockQNameIter : lockQNames)
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{
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String localname = lockQNameIter.getLocalName();
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// Get the basic lock resource, forcing a create
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// TODO: Pull back all lock resources in a single query
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LockResourceEntity lockResource = getLockResource(qnameNamespaceId, localname);
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if (lockResource == null)
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{
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// Create it
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lockResource = createLockResource(qnameNamespaceId, localname);
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}
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requiredLockResourceIds.add(lockResource.getId());
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}
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// Now, get all locks for the resources we will need
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List<LockEntity> existingLocks = getLocks(requiredLockResourceIds);
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Map<LockEntity, LockEntity> existingLocksMap = new HashMap<LockEntity, LockEntity>();
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// Check them and make sure they don't prevent locks
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for (LockEntity existingLock : existingLocks)
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{
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boolean canTakeLock = canTakeLock(existingLock, lockApplicant, requiredExclusiveLockResourceId);
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if (!canTakeLock)
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{
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return false;
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}
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existingLocksMap.put(existingLock, existingLock);
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}
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// Take the locks for the resources.
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// Existing locks must be updated, if required.
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for (Long requiredLockResourceId : requiredLockResourceIds)
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{
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LockEntity requiredLock = new LockEntity();
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requiredLock.setSharedResourceId(requiredLockResourceId);
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requiredLock.setExclusiveResourceId(requiredExclusiveLockResourceId);
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// Does it exist?
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if (existingLocksMap.containsKey(requiredLock))
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{
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requiredLock = existingLocksMap.get(requiredLock);
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// Do an update
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throw new UnsupportedOperationException();
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}
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else
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{
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// Create it
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requiredLock = createLock(
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requiredLockResourceId,
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requiredExclusiveLockResourceId,
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lockApplicant,
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timeToLive);
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}
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}
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return true;
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}
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private boolean canTakeLock(LockEntity existingLock, String lockApplicant, Long desiredExclusiveLock)
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{
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if (EqualsHelper.nullSafeEquals(existingLock.getLockHolder(), lockApplicant))
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{
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// The lock applicant to be is also the current lock holder.
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// Regardless of lock expiry, the lock can be taken
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return true;
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}
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else if (existingLock.hasExpired())
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{
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// Expired locks are fair game
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return true;
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}
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else if (existingLock.isExclusive())
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{
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// It's a valid, exclusive lock held by someone else ...
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return false;
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}
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else if (desiredExclusiveLock.equals(existingLock.getSharedResourceId()))
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{
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// We can't take an exclusive lock if a shared lock is active
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return false;
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}
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else
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{
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// Good to go
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return true;
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}
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}
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/**
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* Override to get the unique, lock resource entity if one exists.
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*
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* @param qnameNamespaceId the namespace entity ID
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* @param qnameLocalName the lock localname
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* @return Returns the lock resource entity,
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* or <tt>null</tt> if it doesn't exist
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*/
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protected abstract LockResourceEntity getLockResource(Long qnameNamespaceId, String qnameLocalName);
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/**
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* Create a unique lock resource
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*
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* @param qnameNamespaceId the namespace entity ID
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* @param qnameLocalName the lock localname
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* @return Returns the newly created lock resource entity
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*/
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protected abstract LockResourceEntity createLockResource(Long qnameNamespaceId, String qnameLocalName);
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/**
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* Get any existing lock data for the resources required. The locks returned are not filtered and
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* may be expired.
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*
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* @param lockResourceIds a list of resource IDs for which to retrieve the current locks
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* @return Returns a list of locks (expired or not) for the given lock resources
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*/
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protected abstract List<LockEntity> getLocks(List<Long> lockResourceIds);
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/**
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* Create a new lock.
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* @param sharedResourceId the specific resource to lock
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* @param exclusiveResourceId the exclusive lock that is being sought
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* @param lockApplicant the ID of the lock applicant
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* @param timeToLive the time, in milliseconds, for the lock to remain valid
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* @return Returns the new lock
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* @throws ConcurrencyFailureException if the lock was already taken at the time of creation
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*/
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protected abstract LockEntity createLock(
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Long sharedResourceId,
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Long exclusiveResourceId,
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String lockApplicant,
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long timeToLive);
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/**
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* Split a lock's qualified name into the component parts using the '.' (period) as a
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* separator on the localname. The namespace is preserved. The provided qualified
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* name will always be the last component in the returned list.
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*
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* @param lockQName the lock name to split into it's higher-level paths
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* @return Returns the namespace ID along with the ordered localnames
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*/
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protected List<QName> splitLockQName(QName lockQName)
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{
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String ns = lockQName.getNamespaceURI();
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String name = lockQName.getLocalName();
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StringTokenizer tokenizer = new StringTokenizer(name, ".");
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List<QName> ret = new ArrayList<QName>(tokenizer.countTokens());
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StringBuilder sb = new StringBuilder();
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// Fill it
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boolean first = true;
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while (tokenizer.hasMoreTokens())
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{
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if (first)
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{
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first = false;
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}
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else
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{
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sb.append(".");
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}
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sb.append(tokenizer.nextToken());
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QName parentLockQName = QName.createQName(ns, sb.toString());
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ret.add(parentLockQName);
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}
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// Done
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return ret;
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}
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}
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