indexer-core/src/main/java/org/apache/maven/index/context/TrackingLockFactory.java

/*
 * 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.maven.index.context;

import java.io.IOException;
import java.util.Collections;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.Lock;
import org.apache.lucene.store.LockFactory;
import static com.google.common.base.Preconditions.checkNotNull;
import java.util.HashSet;

/**
 *
 * @author Tomas Zezula
 */
final class TrackingLockFactory extends LockFactory {

    private final LockFactory delegate;
    private final Set<TrackingLock> emittedLocks;

    TrackingLockFactory(final LockFactory delegate) {
        this.delegate = checkNotNull(delegate);
        this.emittedLocks = Collections.newSetFromMap(new ConcurrentHashMap<TrackingLock,Boolean>());
    }

    Set<? extends Lock> getEmittedLocks(String name) {
        final Set<Lock> result = new HashSet<>();
        for (TrackingLock lock : emittedLocks) {
            if (name == null || name.equals(lock.getName())) {
                result.add(lock);
            }
        }
        return result;
    }

    @Override
    public Lock obtainLock(Directory dir, String lockName) throws IOException {
        final TrackingLock lck = new TrackingLock(
                delegate.obtainLock(dir, lockName),
                lockName);
        emittedLocks.add(lck);
        return lck;
    }


    private final class TrackingLock extends Lock {
        private final Lock delegate;
        private final String name;

        TrackingLock(
                final Lock delegate,
                final String name) {
            this.delegate = checkNotNull(delegate);
            this.name = checkNotNull(name);
        }

        String getName() {
            return name;
        }

        @Override
        public void close() throws IOException {
            try {
                delegate.close();
            } finally {
                emittedLocks.remove(this);
            }
        }

        @Override
        public void ensureValid() throws IOException {
            delegate.ensureValid();
        }
    }
}