org.apache.webbeans.context.creational.BeanInstanceBag Maven / Gradle / Ivy

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/*
 * 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.webbeans.context.creational;

import javax.enterprise.context.spi.Contextual;
import javax.enterprise.context.spi.CreationalContext;
import java.io.Serializable;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Stores the CreationalContext and the Contextual Instance.
 * This also makes sure that we don't create the same bean
 * twice.
 */
public class BeanInstanceBag implements Serializable
{
    private static final long serialVersionUID = 1656996021599122499L;
    private final CreationalContext beanCreationalContext;
    
    private T beanInstance;
    
    private final Lock lock = new ReentrantLock();
    
    public BeanInstanceBag(CreationalContext beanCreationalContext)
    {
        this.beanCreationalContext = beanCreationalContext;
    }

    /**
     * @return the beanCreationalContext
     */
    public CreationalContext getBeanCreationalContext()
    {
        return beanCreationalContext;
    }

    /**
     * @return the beanInstance
     */
    public T getBeanInstance()
    {
        return beanInstance;
    }

    /**
     * Create the contextual instance in a thread safe fashion
     * @param contextual
     * @return the single contextual instance for the context
     */
    public T create(Contextual contextual)
    {
        try
        {
            lock.lock();
            
            // we need to check again, maybe we got blocked by a previous invocation
            if (beanInstance == null)
            {
                beanInstance = contextual.create(beanCreationalContext);
            }
            
        }
        finally
        {
            lock.unlock();
        }
        
        return beanInstance; 
    }

    @Override
    public String toString()
    {
        return "Bag:" + beanCreationalContext + ", Instance: " + beanInstance;
    }
}