content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.journal;
  
  import alluxio.proto.journal.Journal;
  import alluxio.resource.CloseableIterator;
  import alluxio.util.CommonUtils;
  
  /**
   * Journaled component responsible for journaling a single journal entry.
   */
  public abstract class SingleEntryJournaled implements Journaled {
  
    private Journal.JournalEntry mEntry = Journal.JournalEntry.getDefaultInstance();
  
    @Override
    public CloseableIterator<Journal.JournalEntry> getJournalEntryIterator() {
      return CloseableIterator.noopCloseable(CommonUtils.singleElementIterator(mEntry));
    }
  
    @Override
    public boolean processJournalEntry(Journal.JournalEntry entry) {
      if (!Journal.JournalEntry.getDefaultInstance().equals(mEntry)) {
        LOG.warn("{} has already processed an entry", getCheckpointName());
      }
      mEntry = entry;
      return true;
    }
  
    @Override
    public void resetState() {
      mEntry = Journal.JournalEntry.getDefaultInstance();
    }
  
    /**
     * @return the entry stored by this object
     */
    public Journal.JournalEntry getEntry() {
      if (Journal.JournalEntry.getDefaultInstance().equals(mEntry)) {
        LOG.warn("{} has not processed any entries", getCheckpointName());
      }
      return mEntry;
    }
  }
  