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DSpace core data model and service APIs.

There is a newer version: 8.0

/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.dspace.checker;

import java.sql.SQLException;

import org.dspace.content.Bitstream;

/**
 * 
 * BitstreamDispatchers are strategy objects that hand bitstream ids out to
 * workers. Implementations must be threadsafe.
 * 
 *
 * 
 * The rationale behind the use of the Sentinel pattern (rather than the more
 * traditional iterator pattern or a cursor c.f. java.sql.ResultSet): -
 * 
 * 
 * To make it easy to make implementations thread safe - multithreaded
 * invocation of the dispatchers is seen as a next step use case. In simple
 * terms, this requires that a single method does all the work.
 * Shouldn't an exception as the sentinel, as reaching the end of a loop is
 * not an exceptional condition.
 * 
 *
 * @author Jim Downing
 * @author Grace Carpenter
 * @author Nathan Sarr
 */
public interface BitstreamDispatcher {
    /**
     * This value should be returned by next() to indicate that
     * there are no more values.
     */
    public static int SENTINEL = -1;

    /**
     * Returns the next id for checking, or a sentinel value if there are no
     * more to check.
     *
     * @return the next bitstream id, or BitstreamDispatcher.SENTINEL if there
     * isn't another value
     * @throws SQLException if database error
     */
    public Bitstream next() throws SQLException;
}