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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * 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.rapiddweller.common;

import java.io.Closeable;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;

/**
 * Generates consecutive sequence values and persists sequence state in a properties file.
 * Created: 09.11.2013 09:04:51
 *
 * @author Volker Bergmann
 * @since 0.5.25
 */
public class LocalSequenceProvider implements Closeable {

  private static final Map INSTANCES = new HashMap<>();

  /**
   * Gets instance.
   *
   * @param filename the filename
   * @return the instance
   */
  public static LocalSequenceProvider getInstance(String filename) {
    LocalSequenceProvider result = INSTANCES.get(filename);
    if (result == null) {
      result = new LocalSequenceProvider(filename);
      INSTANCES.put(filename, result);
    }
    return result;
  }


  private final String fileName;

  private boolean cached;

  private final Map counters;

  // Initialization --------------------------------------------------------------------------------------------------

  private LocalSequenceProvider(String fileName) {
    this(fileName, true);
  }

  private LocalSequenceProvider(String fileName, boolean cached) {
    this.fileName = fileName;
    this.cached = cached;
    this.counters = new HashMap<>();
    load();
  }

  // Properties ------------------------------------------------------------------------------------------------------

  /**
   * Is cached boolean.
   *
   * @return the boolean
   */
  public boolean isCached() {
    return cached;
  }

  /**
   * Sets cached.
   *
   * @param cached the cached
   */
  public void setCached(boolean cached) {
    this.cached = cached;
  }


  // interface -------------------------------------------------------------------------------------------------------

  /**
   * Next long.
   *
   * @param sequenceName the sequence name
   * @return the long
   */
  public long next(String sequenceName) {
    long result = getOrCreateCounter(sequenceName).incrementAndGet();
    if (!cached) {
      save();
    }
    return result;
  }

  @Override
  public void close() {
    save();
  }


  // static methods --------------------------------------------------------------------------------------------------

  /**
   * Save.
   */
  public void save() {
    Map values = new HashMap<>();
    for (Map.Entry entry : counters.entrySet()) {
      values.put(entry.getKey(), String.valueOf(entry.getValue().get()));
    }
    try {
      IOUtil.writeProperties(values, fileName);
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }


  // private helpers -------------------------------------------------------------------------------------------------

  private void load() {
    if (IOUtil.isURIAvailable(fileName)) {
      try {
        Map values = IOUtil.readProperties(fileName);
        for (Map.Entry entry : values.entrySet()) {
          counters.put(entry.getKey(), new AtomicLong(Long.parseLong(entry.getValue())));
        }
      } catch (Exception e) {
        throw new ConfigurationError(e);
      }
    }
  }

  private AtomicLong getOrCreateCounter(String name) {
    AtomicLong counter = counters.get(name);
    if (counter == null) {
      counter = new AtomicLong();
      counters.put(name, counter);
    }
    return counter;
  }

}