/*
* Copyright (c) 2008-2017, Hazelcast, Inc. 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.
*/
package com.hazelcast.concurrent.lock;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.SerializableByConvention;
import com.hazelcast.spi.ObjectNamespace;
import com.hazelcast.spi.impl.operationparker.impl.OperationParkerImpl;
import java.io.IOException;
import static com.hazelcast.nio.serialization.SerializableByConvention.Reason.PUBLIC_API;
/**
* A specialization of {@link ObjectNamespace} intended to be used by ILock proxies.
*
* It intentionally <b>does not</b> use {@link #name} field in <code>equals()</code>
* and <code>hashcode()</code> methods. This is a hack to share a single instance of
* {@link LockStore} for all ILocks proxies (per partition).
*
* Discussion:
*
* If we included the name in equals()/hashcode() methods then each ILock would create
* its own {@link LockStoreImpl}. Each <code>LockStoreImpl</code> contains additional
* mapping key -> LockResource. However ILock proxies always use a single key only
* thus creating a <code>LockStoreImpl</code> for each ILock would introduce an unnecessary
* indirection and memory waster. Also each LockStoreImpl is maintaining its own
* scheduler for lock eviction purposes, etc.
*
* I originally wanted to remove the <code>name</code> field and use a constant,
* but it has side-effects - for example when a ILock proxy is destroyed then you
* want to destroy all pending {@link com.hazelcast.spi.BlockingOperation}
*
* @see LockStoreContainer#getOrCreateLockStore(ObjectNamespace)
* @see OperationParkerImpl#cancelParkedOperations(String, Object, Throwable)
*
*/
@SerializableByConvention(PUBLIC_API)
public final class InternalLockNamespace implements ObjectNamespace {
private String name;
public InternalLockNamespace() {
}
public InternalLockNamespace(String name) {
this.name = name;
}
@Override
public String getServiceName() {
return LockService.SERVICE_NAME;
}
@Override
public String getObjectName() {
return name;
}
@Override
public void writeData(ObjectDataOutput out) throws IOException {
out.writeUTF(name);
}
@Override
public void readData(ObjectDataInput in) throws IOException {
name = in.readUTF();
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
//warning: this intentionally does not use name field see class-level JavaDoc above
return true;
}
@Override
public int hashCode() {
//warning: this intentionally does not use name field see class-level JavaDoc above
return getServiceName().hashCode();
}
@Override
public String toString() {
return "InternalLockNamespace{service='" + LockService.SERVICE_NAME + '\'' + ", objectName=" + name + '}';
}
}