GameObjectOutputStream.java

package games.strategy.engine.data;

import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.OutputStream;

/**
 * To maintain == relationships and the singleton nature of many classes in GameData
 * we do some work in the ObjectSteam.
 * For example, when we serialize a Territory over a GameObjectOutputStream,
 * we do not send an instance of Territory, but rather a marker saying that this is the territory,
 * and this is its name. When it comes time for a GameObjectOutputStream
 * to read the territory on the other side, the territory name is read, and the territory returned
 * by the GameObjectInputStream is the territory with that name beloning to the GameData associated
 * with the GameObjectInputStream.
 * This ensures the state of the territory remains consistent.
 */
public class GameObjectOutputStream extends ObjectOutputStream {
  /**
   * Creates a new instance of GameObjectOutputStream.
   *
   * @param output
   *        output stream
   */
  public GameObjectOutputStream(final OutputStream output) throws IOException {
    super(output);
    enableReplaceObject(true);
  }

  @Override
  protected Object replaceObject(final Object obj) throws IOException {
    if (obj instanceof Named) {
      final Named named = (Named) obj;
      if (GameObjectStreamData.canSerialize(named)) {
        return new GameObjectStreamData(named);
      }
    }
    return obj;
  }
}