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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2018 AT&T Intellectual Property. 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.drools.core.lock;
import static org.onap.policy.drools.core.lock.LockRequestFuture.MSG_NULL_OWNER;
import static org.onap.policy.drools.core.lock.LockRequestFuture.MSG_NULL_RESOURCE_ID;
import static org.onap.policy.drools.core.lock.LockRequestFuture.makeNullArgException;
import java.util.List;
import java.util.concurrent.Future;
import java.util.function.Function;
import org.onap.policy.drools.core.lock.PolicyResourceLockFeatureAPI.Callback;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Manager of resource locks. Checks for API implementers.
*/
public class PolicyResourceLockManager extends SimpleLockManager {
private static Logger logger = LoggerFactory.getLogger(PolicyResourceLockManager.class);
/**
* Used to access various objects.
*/
public static Factory factory = new Factory();
/**
* Used by junit tests.
*/
protected PolicyResourceLockManager() {
super();
}
/**
*
* @return the manager singleton
*/
public static PolicyResourceLockManager getInstance() {
return Singleton.instance;
}
protected static Factory getFactory() {
return factory;
}
/**
* Sets the factory to be used by junit tests.
*
* @param factory
*/
protected static void setFactory(Factory factory) {
PolicyResourceLockManager.factory = factory;
}
@Override
public Future<Boolean> lock(String resourceId, String owner, Callback callback) {
if (resourceId == null) {
throw makeNullArgException(MSG_NULL_RESOURCE_ID);
}
if (owner == null) {
throw makeNullArgException(MSG_NULL_OWNER);
}
Future<Boolean> result = doIntercept(null, impl -> impl.beforeLock(resourceId, owner, callback));
if (result != null) {
return result;
}
// implementer didn't do the work - use superclass
result = super.lock(resourceId, owner, callback);
boolean locked = ((LockRequestFuture) result).isLocked();
doIntercept(false, impl -> impl.afterLock(resourceId, owner, locked));
return result;
}
@Override
public boolean unlock(String resourceId, String owner) {
if (resourceId == null) {
throw makeNullArgException(MSG_NULL_RESOURCE_ID);
}
if (owner == null) {
throw makeNullArgException(MSG_NULL_OWNER);
}
Boolean result = doIntercept(null, impl -> impl.beforeUnlock(resourceId, owner));
if (result != null) {
return result;
}
// implementer didn't do the work - use superclass
boolean unlocked = super.unlock(resourceId, owner);
doIntercept(false, impl -> impl.afterUnlock(resourceId, owner, unlocked));
return unlocked;
}
/**
*
* @throws IllegalArgumentException if the resourceId is {@code null}
*/
@Override
public boolean isLocked(String resourceId) {
if (resourceId == null) {
throw makeNullArgException(MSG_NULL_RESOURCE_ID);
}
Boolean result = doIntercept(null, impl -> impl.beforeIsLocked(resourceId));
if (result != null) {
return result;
}
return super.isLocked(resourceId);
}
/**
*
* @throws IllegalArgumentException if the resourceId or owner is {@code null}
*/
@Override
public boolean isLockedBy(String resourceId, String owner) {
if (resourceId == null) {
throw makeNullArgException(MSG_NULL_RESOURCE_ID);
}
if (owner == null) {
throw makeNullArgException(MSG_NULL_OWNER);
}
Boolean result = doIntercept(null, impl -> impl.beforeIsLockedBy(resourceId, owner));
if (result != null) {
return result;
}
return super.isLockedBy(resourceId, owner);
}
/**
* Applies a function to each implementer of the lock feature. Returns as soon as one
* of them returns a non-null value.
*
* @param continueValue if the implementer returns this value, then it continues to
* check addition implementers
* @param func function to be applied to the implementers
* @return first non-null value returned by an implementer, <i>continueValue<i/> if
* they all returned <i>continueValue<i/>
*/
public static <T> T doIntercept(T continueValue, Function<PolicyResourceLockFeatureAPI, T> func) {
for (PolicyResourceLockFeatureAPI impl : factory.getImplementers()) {
try {
T result = func.apply(impl);
if (result != continueValue) {
return result;
}
} catch (RuntimeException e) {
logger.warn("lock feature {} threw an exception", impl, e);
}
}
return continueValue;
}
/**
* Initialization-on-demand holder idiom.
*/
private static class Singleton {
private static final PolicyResourceLockManager instance = new PolicyResourceLockManager();
}
/**
* Used to access various objects.
*/
public static class Factory {
/**
*
* @return the list of feature implementers
*/
public List<PolicyResourceLockFeatureAPI> getImplementers() {
return PolicyResourceLockFeatureAPI.impl.getList();
}
}
}
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