CachedDatabase.java

package com.nicewuerfel.blockown.database;

import com.google.common.base.Optional;

import com.nicewuerfel.blockown.Ownable;
import com.nicewuerfel.blockown.User;
import com.nicewuerfel.blockown.output.Output;

import java.io.File;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.RejectedExecutionException;

import javax.annotation.Nonnull;

public abstract class CachedDatabase extends Database {

  final CacheAccessor cache;

  CachedDatabase(Output output, File pluginFolder) {
    super(output);
    cache = new CacheAccessor(this, pluginFolder);
  }

  @Override
  public Optional<User> getOwner(@Nonnull Ownable ownable) {
    return cache.getOwner(ownable);
  }

  @Override
  public void enqueue(DatabaseAction databaseAction) {
    try {
      getThreadPool().execute(new CachedDatabaseOperation(this, databaseAction));
    } catch (RejectedExecutionException ignored) {
      getOutput().printConsole("Couldn't execute DatabaseAction");
    }
  }

  /**
   * Flush cache data to database. Removes each flushed key-value-pair from the given {@link Map}.
   *
   * @param cacheData the cache data
   * @return true, if successful
   */
  boolean flushDatabase(@Nonnull final Map<Ownable, Optional<User>> cacheData) {
    Iterator<Entry<Ownable, Optional<User>>> iterator = cacheData.entrySet().iterator();
    Entry<Ownable, Optional<User>> owning;
    while (iterator.hasNext()) {
      owning = iterator.next();
      DatabaseAction action;
      Ownable key = owning.getKey();
      Optional<User> value = owning.getValue();
      if (!value.isPresent()) {
        action = DatabaseAction.newUnownInstance(key);
      } else {
        action = DatabaseAction.newOwnInstance(key, value.get());
      }

      if (!setDatabaseOwner(action)) {
        return false;
      }
      iterator.remove();
    }
    return true;
  }

  @Override
  public void close() {
    cache.close();
    super.close();
  }
}