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Berkeley DB Java Edition is a open source, transactional storage solution for Java applications. The Direct Persistence Layer (DPL) API is faster and easier to develop, deploy, and manage than serialized object files or ORM-based Java persistence solutions. The Collections API enhances the standard java.util.collections classes allowing them to be persisted to a local file system and accessed concurrently while protected by ACID transactions. Data is stored by serializing objects and managing class and instance data separately so as not to waste space. Berkeley DB Java Edition is the reliable drop-in solution for complex, fast, and scalable storage. Source for this release is in 'je-4.0.92-sources.jar', the Javadoc is located at 'http://download.oracle.com/berkeley-db/docs/je/4.0.92/'.

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/*-
 * Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle Berkeley
 * DB Java Edition made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle Berkeley DB Java Edition for a copy of the
 * license and additional information.
 */

package com.sleepycat.persist.impl;

import com.sleepycat.bind.tuple.TupleBase;
import com.sleepycat.compat.DbCompat;
import com.sleepycat.je.DatabaseEntry;
import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Sequence;

/**
 * Assigns primary keys from a Sequence.
 *
 * This class is used directly by PrimaryIndex, not via an interface.  To avoid
 * making a public interface, the PersistEntityBinding contains a reference to
 * a PersistKeyAssigner, and the PrimaryIndex gets the key assigner from the
 * binding.  See the PrimaryIndex constructor for more information.
 *
 * @author Mark Hayes
 */
public class PersistKeyAssigner {

    /* See Store.refresh for an explanation of the use of volatile fields. */
    private volatile Catalog catalog;
    private volatile Format keyFieldFormat;
    private volatile Format entityFormat;
    private final boolean rawAccess;
    private final Sequence sequence;

    PersistKeyAssigner(PersistKeyBinding keyBinding,
                       PersistEntityBinding entityBinding,
                       Sequence sequence) {
        catalog = keyBinding.catalog;
        /* getSequenceKeyFormat will validate the field type for a sequence. */
        keyFieldFormat = keyBinding.keyFormat.getSequenceKeyFormat();
        entityFormat = entityBinding.entityFormat;
        rawAccess = entityBinding.rawAccess;
        this.sequence = sequence;
    }

    public boolean assignPrimaryKey(Object entity, DatabaseEntry key)
        throws DatabaseException {

        try {
            return assignPrimaryKeyInternal(entity, key);
        } catch (RefreshException e) {
            e.refresh();
            try {
                return assignPrimaryKeyInternal(entity, key);
            } catch (RefreshException e2) {
                throw DbCompat.unexpectedException(e2);
            }
        }
    }

    private boolean assignPrimaryKeyInternal(Object entity, DatabaseEntry key)
        throws DatabaseException, RefreshException {
            
        /*
         * The keyFieldFormat is the format of a simple integer field.  For a
         * composite key class it is the contained integer field.  By writing
         * the Long sequence value using that format, the output data can then
         * be read to construct the actual key instance, whether it is a simple
         * or composite key class, and assign it to the primary key field in
         * the entity object.
         */
        if (entityFormat.isPriKeyNullOrZero(entity, rawAccess)) {
            Long value = sequence.get(null, 1);
            RecordOutput output = new RecordOutput(catalog, rawAccess);
            keyFieldFormat.writeObject(value, output, rawAccess);
            TupleBase.outputToEntry(output, key);
            EntityInput input = new RecordInput
                (catalog, rawAccess, null, 0,
                 key.getData(), key.getOffset(), key.getSize());
            entityFormat.getReader().readPriKey(entity, input, rawAccess);
            return true;
        } else {
            return false;
        }
    }

    /**
     * See Store.refresh.
     */
    void refresh(final PersistCatalog newCatalog) {
        catalog = newCatalog;
        entityFormat = catalog.getFormat(entityFormat.getClassName());
        keyFieldFormat = catalog.getFormat(keyFieldFormat.getClassName());
    }
}