001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *  
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *  
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License. 
018 *  
019 */
020package org.apache.directory.server.xdbm;
021
022
023import org.apache.directory.api.ldap.model.cursor.AbstractCursor;
024import org.apache.directory.api.ldap.model.cursor.CursorException;
025import org.apache.directory.api.ldap.model.exception.LdapException;
026import org.apache.directory.server.core.api.partition.PartitionTxn;
027
028
029/**
030 * An abstract Cursor used by the index cursors.
031 *
032 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
033 */
034public abstract class AbstractIndexCursor<V> extends AbstractCursor<IndexEntry<V, String>>
035{
036    /** Tells if there are some element available in the cursor */
037    private boolean available = false;
038    
039    /** A transaction associated with this cursor */
040    protected PartitionTxn partitionTxn;
041
042    /** The message used for unsupported operations */
043    protected static final String UNSUPPORTED_MSG = "Unsupported operation";
044
045
046    /**
047     * {@inheritDoc}
048     */
049    public boolean available()
050    {
051        return available;
052    }
053
054
055    /**
056     * Gets the message to return for operations that are not supported
057     * 
058     * @return The Unsupported message
059     */
060    protected abstract String getUnsupportedMessage();
061
062
063    /**
064     * {@inheritDoc}
065     */
066    public void after( IndexEntry<V, String> element ) throws LdapException, CursorException
067    {
068        throw new UnsupportedOperationException( getUnsupportedMessage() );
069    }
070
071
072    /**
073     * {@inheritDoc}
074     */
075    public void before( IndexEntry<V, String> element ) throws LdapException, CursorException
076    {
077        throw new UnsupportedOperationException( getUnsupportedMessage() );
078    }
079
080
081    /**
082     * {@inheritDoc}
083     */
084    protected boolean setAvailable( boolean available )
085    {
086        this.available = available;
087        return available;
088    }
089    
090
091
092    @Override
093    public boolean previous() throws LdapException, CursorException
094    {
095        return false;
096    }
097
098
099    @Override
100    public boolean next() throws LdapException, CursorException
101    {
102        return false;
103    }
104}