GameModel.java

package scorekeep;

import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBQueryExpression;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class GameModel {
  /** AWS SDK credentials. */
  private AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard()
        .build();
  private DynamoDBMapper mapper = new DynamoDBMapper(client);
  private final SessionModel sessionModel = new SessionModel();

  public void saveGame(Game game) throws SessionNotFoundException {
    // check session
    String sessionId = game.getSession();
    if (sessionModel.loadSession(sessionId) == null ) {
      throw new SessionNotFoundException(sessionId);
    }
    mapper.save(game);
  }

  public Game loadGame(String gameId) throws GameNotFoundException {
    Game game = mapper.load(Game.class, gameId);
    if ( game == null ) {
      throw new GameNotFoundException(gameId);
    }
    return game;
  }

  public List<Game> loadGames(String sessionId) throws SessionNotFoundException {
    if ( sessionModel.loadSession(sessionId) == null ) {
      throw new SessionNotFoundException(sessionId);
    }
    Map<String, AttributeValue> eav = new HashMap<String, AttributeValue>();
    eav.put(":val1", new AttributeValue().withS(sessionId));

    Map<String, String> ean = new HashMap<String, String>();
    ean.put("#key1", "session");

    DynamoDBQueryExpression<Game> queryExpression = new DynamoDBQueryExpression<Game>()
        .withIndexName("session-index")
        .withExpressionAttributeValues(eav)
        .withExpressionAttributeNames(ean)
        .withKeyConditionExpression("#key1 = :val1")
        .withConsistentRead(false);

    List<Game> sessionGames = mapper.query(Game.class, queryExpression);
    return sessionGames;
  }

  public void deleteGame(String sessionId, String gameId) throws GameNotFoundException {
    Game game = mapper.load(Game.class, gameId);
    if ( game == null ) {
      throw new GameNotFoundException(gameId);
    }
    mapper.delete(game);
    //delete game from session
    Session session = mapper.load(Session.class, sessionId);
    Set<String> sessionGames = session.getGames();
    sessionGames.remove(gameId);
    if (sessionGames.size() == 0) {
      session.clearGames();
    } else {
      session.setGames(sessionGames);
    }
    mapper.save(session);
  }
}