lightning-core/src/main/java/org/apache/directmemory/lightning/internal/instantiator/ObjenesisBase.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.directmemory.lightning.internal.instantiator;

import java.util.HashMap;
import java.util.Map;

import org.apache.directmemory.lightning.instantiator.ObjectInstantiator;
import org.apache.directmemory.lightning.instantiator.ObjectInstantiatorFactory;
import org.apache.directmemory.lightning.internal.instantiator.strategy.InstantiatorStrategy;

/**
 * Base class to extend if you want to have a class providing your own default strategy. Can also be instantiated
 * directly.
 * 
 * @author Henri Tremblay
 */
public class ObjenesisBase
    implements ObjectInstantiatorFactory
{

    /** Strategy used by this Objenesi implementation to create classes */
    protected final InstantiatorStrategy strategy;

    /** Strategy cache. Key = Class, Value = InstantiatorStrategy */
    protected Map<String, ObjectInstantiator> cache;

    /**
     * Constructor allowing to pick a strategy and using cache
     * 
     * @param strategy Strategy to use
     */
    public ObjenesisBase( InstantiatorStrategy strategy )
    {
        this( strategy, true );
    }

    /**
     * Flexible constructor allowing to pick the strategy and if caching should be used
     * 
     * @param strategy Strategy to use
     * @param useCache If {@link ObjectInstantiator}s should be cached
     */
    public ObjenesisBase( InstantiatorStrategy strategy, boolean useCache )
    {
        if ( strategy == null )
        {
            throw new IllegalArgumentException( "A strategy can't be null" );
        }
        this.strategy = strategy;
        this.cache = useCache ? new HashMap<String, ObjectInstantiator>() : null;
    }

    @Override
    public String toString()
    {
        return getClass().getName() + " using " + strategy.getClass().getName()
            + ( cache == null ? " without" : " with" ) + " caching";
    }

    /**
     * Will create a new object without any constructor being called
     * 
     * @param clazz Class to instantiate
     * @return New instance of clazz
     */
    @Override
    public Object newInstance( Class<?> clazz )
    {
        return getInstantiatorOf( clazz ).newInstance();
    }

    /**
     * Will pick the best instantiator for the provided class. If you need to create a lot of instances from the same
     * class, it is way more efficient to create them from the same ObjectInstantiator than calling
     * {@link #newInstance(Class)}.<br>
     * Explicitly made this NON-THREADSAFE for performance reasons.
     * 
     * @param clazz Class to instantiate
     * @return Instantiator dedicated to the class
     */
    @Override
    public ObjectInstantiator getInstantiatorOf( Class<?> clazz )
    {
        if ( cache == null )
        {
            return strategy.newInstantiatorOf( clazz );
        }
        ObjectInstantiator instantiator = cache.get( clazz.getName() );
        if ( instantiator == null )
        {
            instantiator = strategy.newInstantiatorOf( clazz );
            cache.put( clazz.getName(), instantiator );
        }
        return instantiator;
    }

}