001package org.eclipse.aether;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 * 
012 *  http://www.apache.org/licenses/LICENSE-2.0
013 * 
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import static java.util.Objects.requireNonNull;
023
024import java.util.concurrent.ConcurrentHashMap;
025import java.util.concurrent.ConcurrentMap;
026import java.util.function.Supplier;
027
028/**
029 * A simple session data storage backed by a thread-safe map.
030 */
031public final class DefaultSessionData
032    implements SessionData
033{
034
035    private final ConcurrentMap<Object, Object> data;
036
037    public DefaultSessionData()
038    {
039        data = new ConcurrentHashMap<>();
040    }
041
042    public void set( Object key, Object value )
043    {
044        requireNonNull( key, "key cannot be null" );
045
046        if ( value != null )
047        {
048            data.put( key, value );
049        }
050        else
051        {
052            data.remove( key );
053        }
054    }
055
056    public boolean set( Object key, Object oldValue, Object newValue )
057    {
058        requireNonNull( key, "key cannot be null" );
059
060        if ( newValue != null )
061        {
062            if ( oldValue == null )
063            {
064                return data.putIfAbsent( key, newValue ) == null;
065            }
066            return data.replace( key, oldValue, newValue );
067        }
068        else
069        {
070            if ( oldValue == null )
071            {
072                return !data.containsKey( key );
073            }
074            return data.remove( key, oldValue );
075        }
076    }
077
078    public Object get( Object key )
079    {
080        requireNonNull( key, "key cannot be null" );
081
082        return data.get( key );
083    }
084
085    public Object computeIfAbsent( Object key, Supplier<Object> supplier )
086    {
087        return data.computeIfAbsent( key, k -> supplier.get() );
088    }
089}