// Copyright 2006, 2008, 2010 The Apache Software Foundation
//
// Licensed 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.tapestry5.ioc.internal.services;

import org.apache.tapestry5.ioc.ObjectCreator;
import org.apache.tapestry5.ioc.services.PerThreadValue;
import org.apache.tapestry5.ioc.services.PerthreadManager;

/**
 * Provides per-thread implementations of services.
 */
public class PerThreadServiceCreator implements ObjectCreator
{
    private final PerThreadValue<Object> perThreadValue;

    private final ObjectCreator delegate;

    public PerThreadServiceCreator(PerthreadManager perthreadManager, ObjectCreator delegate)
    {
        perThreadValue = perthreadManager.createValue();

        this.delegate = delegate;
    }

    /**
     * For each thread, the first call will use the delegate {@link org.apache.tapestry5.ioc.ObjectCreator} to create
     * an instance, and later calls will reuse the same per-thread instance. The instance is stored in the
     * {@link org.apache.tapestry5.ioc.services.PerthreadManager} and will be released at the end of the request.
     */
    public Object createObject()
    {
        if (perThreadValue.exists())
            return perThreadValue.get();

        return perThreadValue.set(delegate.createObject());
    }
}
