storedmap.java

berkeleyDB,强大的嵌入式数据,多个数据库的内核

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000-2004
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: StoredMap.java,v 1.4 2004/09/22 18:01:03 bostic Exp $
 */

package com.sleepycat.collections;

import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import com.sleepycat.bind.EntityBinding;
import com.sleepycat.bind.EntryBinding;
import com.sleepycat.db.Database;

/**
 * A Map view of a {@link Database}.
 *
 * <p><em>Note that this class does not conform to the standard Java
 * collections interface in the following ways:</em></p>
 * <ul>
 * <li>The {@link #size} method always throws
 * <code>UnsupportedOperationException</code> because, for performance reasons,
 * databases do not maintain their total record count.</li>
 * <li>All iterators must be explicitly closed using {@link
 * StoredIterator#close()} or {@link StoredIterator#close(java.util.Iterator)}
 * to release the underlying database cursor resources.</li>
 * </ul>
 *
 * <p>In addition to the standard Map methods, this class provides the
 * following methods for stored maps only.  Note that the use of these methods
 * is not compatible with the standard Java collections interface.</p>
 * <ul>
 * <li>{@link #duplicates(Object)}</li>
 * <li>{@link #append(Object)}</li>
 * </ul>
 *
 * @author Mark Hayes
 */
public class StoredMap extends StoredContainer implements Map {

    private StoredKeySet keySet;
    private boolean keySetInitialized = false;
    private StoredEntrySet entrySet;
    private boolean entrySetInitialized = false;
    private StoredValueSet valueSet;
    private boolean valueSetInitialized = false;

    /**
     * Creates a map view of a {@link Database}.
     *
     * @param database is the Database underlying the new collection.
     *
     * @param keyBinding is the binding used to translate between key buffers
     * and key objects.
     *
     * @param valueBinding is the binding used to translate between value
     * buffers and value objects.
     *
     * @param writeAllowed is true to create a read-write collection or false
     * to create a read-only collection.
     *
     * @throws IllegalArgumentException if formats are not consistently
     * defined or a parameter is invalid.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public StoredMap(Database database, EntryBinding keyBinding,
                     EntryBinding valueBinding, boolean writeAllowed) {

        super(new DataView(database, keyBinding, valueBinding, null,
                           writeAllowed, null));
    }

    /**
     * Creates a map view of a {@link Database} with a {@link
     * PrimaryKeyAssigner}.  Writing is allowed for the created map.
     *
     * @param database is the Database underlying the new collection.
     *
     * @param keyBinding is the binding used to translate between key buffers
     * and key objects.
     *
     * @param valueBinding is the binding used to translate between value
     * buffers and value objects.
     *
     * @param keyAssigner is used by the {@link #append} method to assign
     * primary keys.
     *
     * @throws IllegalArgumentException if formats are not consistently
     * defined or a parameter is invalid.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public StoredMap(Database database, EntryBinding keyBinding,
                     EntryBinding valueBinding,
                     PrimaryKeyAssigner keyAssigner) {

        super(new DataView(database, keyBinding, valueBinding, null,
                           true, keyAssigner));
    }

    protected Object clone()
        throws CloneNotSupportedException {

        // cached collections must be cleared and recreated with the new view
        // of the map to inherit the new view's properties
        StoredMap other = (StoredMap) super.clone();
        other.keySet = null;
	other.keySetInitialized = false;
        other.entrySet = null;
	other.entrySetInitialized = false;
        other.valueSet = null;
	other.valueSetInitialized = false;
        return other;
    }

    /**
     * Creates a map entity view of a {@link Database}.
     *
     * @param database is the Database underlying the new collection.
     *
     * @param keyBinding is the binding used to translate between key buffers
     * and key objects.
     *
     * @param valueEntityBinding is the binding used to translate between
     * key/value buffers and entity value objects.
     *
     * @param writeAllowed is true to create a read-write collection or false
     * to create a read-only collection.
     *
     * @throws IllegalArgumentException if formats are not consistently
     * defined or a parameter is invalid.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public StoredMap(Database database, EntryBinding keyBinding,
                     EntityBinding valueEntityBinding, boolean writeAllowed) {

        super(new DataView(database, keyBinding, null, valueEntityBinding,
                           writeAllowed, null));
    }

    /**
     * Creates a map entity view of a {@link Database} with a {@link
     * PrimaryKeyAssigner}.  Writing is allowed for the created map.
     *
     * @param database is the Database underlying the new collection.
     *
     * @param keyBinding is the binding used to translate between key buffers
     * and key objects.
     *
     * @param valueEntityBinding is the binding used to translate between
     * key/value buffers and entity value objects.
     *
     * @param keyAssigner is used by the {@link #append} method to assign
     * primary keys.
     *
     * @throws IllegalArgumentException if formats are not consistently
     * defined or a parameter is invalid.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public StoredMap(Database database, EntryBinding keyBinding,
                     EntityBinding valueEntityBinding,
                     PrimaryKeyAssigner keyAssigner) {

        super(new DataView(database, keyBinding, null, valueEntityBinding,
                           true, keyAssigner));
    }

    StoredMap(DataView view) {

        super(view);
    }

    /**
     * Returns the value to which this map maps the specified key.  If
     * duplicates are allowed, this method returns the first duplicate, in the
     * order in which duplicates are configured, that maps to the specified
     * key.
     *
     * This method conforms to the {@link Map#get} interface.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public Object get(Object key) {

        return super.get(key);
    }

    /**
     * Associates the specified value with the specified key in this map
     * (optional operation).  If duplicates are allowed and the specified key
     * is already mapped to a value, this method appends the new duplicate
     * after the existing duplicates.  This method conforms to the {@link
     * Map#put} interface.
     *
     * <p>The key parameter may be null if an entity binding is used and the
     * key will be derived from the value (entity) parameter.  If an entity
     * binding is used and the key parameter is non-null, then the key
     * parameter must be equal to the key derived from the value parameter.</p>
     *
     * @return the previous value associated with specified key, or null if
     * there was no mapping for the key or if duplicates are allowed.
     *
     * @throws UnsupportedOperationException if the collection is indexed, or
     * if the collection is read-only.
     *
     * @throws IllegalArgumentException if an entity value binding is used and
     * the primary key of the value given is different than the existing stored
     * primary key.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public Object put(Object key, Object value) {

        return super.put(key, value);
    }

    /**
     * Appends a given value returning the newly assigned key.  If a {@link
     * PrimaryKeyAssigner} is associated with Store for this map, it will be
     * used to assigned the returned key.  Otherwise the Store must be a QUEUE
     * or RECNO database and the next available record number is assigned as
     * the key.  This method does not exist in the standard {@link Map}
     * interface.
     *
     * @param value the value to be appended.
     *
     * @return the assigned key.
     *
     * @throws UnsupportedOperationException if the collection is indexed, or
     * if the collection is read-only, or if the Store has no {@link
     * PrimaryKeyAssigner} and is not a QUEUE or RECNO database.
     *
     * @throws RuntimeExceptionWrapper if a {@link
     * com.sleepycat.db.DatabaseException} is thrown.
     */
    public Object append(Object value) {

        boolean doAutoCommit = beginAutoCommit();
        try {
            Object[] key = new Object[1];