MarshalledTupleKeyEntity.java   [plain text]

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000,2008 Oracle.  All rights reserved.
 *
 * $Id: MarshalledTupleKeyEntity.java,v 12.7 2008/02/07 17:12:25 mark Exp $
 */

package com.sleepycat.bind.tuple;

/**
 * A marshalling interface implemented by entity classes that represent keys as
 * tuples. Since <code>MarshalledTupleKeyEntity</code> objects are instantiated
 * using Java deserialization, no particular constructor is required by classes
 * that implement this interface.
 *
 * <p>Note that a marshalled tuple key extractor is somewhat less efficient
 * than a non-marshalled key tuple extractor because more conversions are
 * needed.  A marshalled key extractor must convert the entry to an object in
 * order to extract the key fields, while an unmarshalled key extractor does
 * not.</p>
 *
 * @author Mark Hayes
 * @see TupleTupleMarshalledBinding
 * @see com.sleepycat.bind.serial.TupleSerialMarshalledBinding
 */
public interface MarshalledTupleKeyEntity {

    /**
     * Extracts the entity's primary key and writes it to the key output.
     *
     * @param keyOutput is the output tuple.
     */
    void marshalPrimaryKey(TupleOutput keyOutput);

    /**
     * Completes construction of the entity by setting its primary key from the
     * stored primary key.
     *
     * @param keyInput is the input tuple.
     */
    void unmarshalPrimaryKey(TupleInput keyInput);

    /**
     * Extracts the entity's secondary key and writes it to the key output.
     *
     * @param keyName identifies the secondary key.
     *
     * @param keyOutput is the output tuple.
     *
     * @return true if a key was created, or false to indicate that the key is
     * not present.
     */
    boolean marshalSecondaryKey(String keyName, TupleOutput keyOutput);

    /**
     * Clears the entity's secondary key fields for the given key name.
     *
     * <p>The specified index key should be changed by this method such that
     * {@link #marshalSecondaryKey} for the same key name will return false.
     * Other fields in the data object should remain unchanged.</p>
     *
     * <p>If {@link com.sleepycat.db.ForeignKeyDeleteAction#NULLIFY} was
     * specified when opening the secondary database, this method is called
     * when the entity for this foreign key is deleted.  If NULLIFY was not
     * specified, this method will not be called and may always return
     * false.</p>
     *
     * @param keyName identifies the secondary key.
     *
     * @return true if the key was cleared, or false to indicate that the key
     * is not present and no change is necessary.
     */
    boolean nullifyForeignKey(String keyName);
}