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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.openjpa.slice;
import java.util.List;
import org.apache.openjpa.kernel.OpenJPAStateManager;
import org.apache.openjpa.lib.util.Localizer;
import org.apache.openjpa.util.UserException;
/**
* Utility methods to determine the target slices for a persistence capable
* instance by calling back to user-specified distribution policy.
*
* @author Pinaki Poddar
*
*/
public class SliceImplHelper {
private static final Localizer _loc =
Localizer.forPackage(SliceImplHelper.class);
/**
* Gets the target slices by calling user-specified {@link DistributionPolicy} or {@link ReplicationPolicy}
* depending on whether the given instance is {@link DistributedConfiguration#isReplicated(Class) replicated}.
* The policy is invoked when an instance enters the managed life cycle. However, if the instance
* being persisted is distributed to a target slice that is not determinable by its own basic attributes,
* but on its associated instance then those association may not have been initialized at the point of entry.
* In such case, the policy may return null. However, when a target slice may not be determinable at the
* entry to managed life cycle, a target slice must be determinable by the time an instance is flushed.
*
* @param pc the managed instance whose target slice is to be determined.
* @param conf to supply the distribution policy
* @param ctx the (opaque) context of invocation. No semantics is currently associated.
*
* @return information about the target slice for the given instance. Can be null if the policy
* can not determine the target slice(s) based on the current state of the instance.
*/
public static SliceInfo getSlicesByPolicy(Object pc, DistributedConfiguration conf, Object ctx) {
List actives = conf.getActiveSliceNames();
Object policy = null;
String[] targets = null;
boolean replicated = isReplicated(pc, conf);
if (replicated) {
policy = conf.getReplicationPolicyInstance();
targets = ((ReplicationPolicy)policy).replicate(pc, actives, ctx);
assertSlices(targets, pc, conf.getActiveSliceNames(), policy);
} else {
policy = conf.getDistributionPolicyInstance();
String target = ((DistributionPolicy)policy).distribute(pc, actives, ctx);
if (target != null) {
targets = new String[]{target};
assertSlices(targets, pc, conf.getActiveSliceNames(), policy);
}
}
return targets != null ? new SliceInfo(replicated, targets) : null;
}
private static void assertSlices(String[] targets, Object pc, List actives, Object policy) {
if (targets == null || targets.length == 0)
throw new UserException(_loc.get("no-policy-slice", new Object[] {
policy.getClass().getName(), pc, actives}));
for (String target : targets)
if (!actives.contains(target))
throw new UserException(_loc.get("bad-policy-slice",
new Object[] {policy.getClass().getName(), target, pc,
actives}));
}
/**
* Gets the target slices for the given StateManager.
*/
public static SliceInfo getSlicesByPolicy(OpenJPAStateManager sm,
DistributedConfiguration conf, Object ctx) {
return getSlicesByPolicy(sm.getPersistenceCapable(), conf, ctx);
}
/**
* Affirms if the given instance be replicated to multiple slices.
*/
public static boolean isReplicated(Object pc, DistributedConfiguration conf) {
return pc == null ? false : conf.isReplicated(pc.getClass());
}
/**
* Affirms if the given StateManager has an assigned slice.
*/
public static boolean isSliceAssigned(OpenJPAStateManager sm) {
return sm != null && sm.getImplData() != null
&& sm.getImplData() instanceof SliceInfo;
}
/**
* Gets the assigned slice information, if any, from the given StateManager.
*/
public static SliceInfo getSliceInfo(OpenJPAStateManager sm) {
return isSliceAssigned(sm) ? (SliceInfo) sm.getImplData() : null;
}
}
