src/java/org/apache/nutch/util/ObjectCache.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.nutch.util;

import java.lang.invoke.MethodHandles;
import java.util.HashMap;
import java.util.WeakHashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;

public class ObjectCache {

  private static final Logger LOG = LoggerFactory
      .getLogger(MethodHandles.lookup().lookupClass());

  private static final WeakHashMap<Configuration, ObjectCache> CACHE = new WeakHashMap<>();

  private final HashMap<String, Object> objectMap;

  private ObjectCache() {
    objectMap = new HashMap<>();
  }

  public synchronized static ObjectCache get(Configuration conf) {
    ObjectCache objectCache = CACHE.get(conf);
    if (objectCache == null) {
      LOG.debug("No object cache found for conf=" + conf
          + ", instantiating a new object cache");
      objectCache = new ObjectCache();
      CACHE.put(conf, objectCache);
    }
    return objectCache;
  }

  public synchronized Object getObject(String key) {
    return objectMap.get(key);
  }

  public boolean hasObject(String key) {
    return objectMap.containsKey(key);
  }

  public synchronized void setObject(String key, Object value) {
    objectMap.put(key, value);
  }
}