001/*
002 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
003 *
004 * This program and the accompanying materials are made available under the
005 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
006 * which accompanies this distribution.  The Eclipse Public License is available
007 * at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
008 * is available at http://www.eclipse.org/org/documents/edl-v10.php.
009 */
010package javax.persistence;
011
012/**
013 * A class that implements this interface can be used to convert
014 * entity attribute state into database column representation
015 * and back again.
016 * Note that the X and Y types may be the same Java type.
017 *
018 * @param X the type of the entity attribute
019 * @param Y the type of the database column
020 * @since Java Persistence 2.1
021 */
022public interface AttributeConverter<X, Y> {
023  /**
024   * Converts the value stored in the entity attribute into the
025   * data representation to be stored in the database.
026   *
027   * @param attribute the entity attribute value to be converted
028   * @return the converted data to be stored in the database column
029   */
030  public Y convertToDatabaseColumn(X attribute);
031
032  /**
033   * Converts the data stored in the database column into the
034   * value to be stored in the entity attribute.
035   * Note that it is the responsibility of the converter writer to
036   * specify the correct dbData type for the corresponding column
037   * for use by the JDBC driver: i.e., persistence providers are
038   * not expected to do such type conversion.
039   *
040   * @param dbData the data from the database column to be converted
041   * @return the converted value to be stored in the entity attribute
042   */
043  public X convertToEntityAttribute(Y dbData);
044}