beancreationlist.java

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/*
 * Copyright 2001-2004 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.commons.betwixt.io.read;

import java.util.ArrayList;
import java.util.Iterator;

/**  
  * <p>Chain implementation that's backed by a list.
  * This is the default implementation used by Betwixt.
  * </p><p>
  * <strong>Note</strong> this implementation is <em>not</em>
  * intended to allow multiple threads of execution to perform
  * modification operations concurrently with traversal of the chain.
  * Users who require this behaviour are advised to create their own implementation.
  * </p>
  *
  * @author Robert Burrell Donkin
  * @since 0.5
  */
public class BeanCreationList extends BeanCreationChain {
    
//-------------------------------------------------------- Class Methods

    /** 
     * Creates the default <code>BeanCreationChain</code> used when reading beans.
     * @return a <code>BeanCreationList</code> with the default creators loader in order, not null
     */
    public static final BeanCreationList createStandardChain() {
        BeanCreationList chain = new BeanCreationList();
        chain.addBeanCreator( ChainedBeanCreatorFactory.createIDREFBeanCreator() );
        chain.addBeanCreator( ChainedBeanCreatorFactory.createDerivedBeanCreator() );
        chain.addBeanCreator( ChainedBeanCreatorFactory.createElementTypeBeanCreator() );
        return chain;
    }
    

    
//-------------------------------------------------------- Attributes
    /** The list backing this chain */
    private ArrayList beanCreators = new ArrayList();
    
//-------------------------------------------------------- Methods
    
    /**
      * Creates an Object based on the given element mapping and read context.
      * Delegates to chain.
      *
      * @param elementMapping the element mapping details
      * @param readContext create against this context 
      * @return the created bean, possibly null
      */
    public Object create( ElementMapping elementMapping, ReadContext readContext ) {
        ChainWorker worker = new ChainWorker();
        return worker.create( elementMapping, readContext );
    }
    
//-------------------------------------------------------- Properties
    
    /**
      * Gets the number of BeanCreators in the wrapped chain.
      * @return the number of <code>ChainedBeanCreator</code>'s in the current chain
      */
    public int getSize() {
        return beanCreators.size();
    }
    
    /**
      * Inserts a <code>BeanCreator</code> at the given position in the chain.
      * Shifts the object currently in that position - and any subsequent elements -
      * to the right.
      *
      * @param index index at which the creator should be inserted
      * @param beanCreator the <code>BeanCreator</code> to be inserted, not null
      * @throws IndexOutOfBoundsException if the index is out of the range 
      * <code>(index < 0 || index > getSize())
      */
    public void insertBeanCreator(
                                int index, 
                                ChainedBeanCreator beanCreator ) 
                                    throws IndexOutOfBoundsException {
        beanCreators.add( index, beanCreator );
    }
    
    /**
      * Adds a <code>BeanCreator</code> to the end of the chain.
      * @param beanCreator the <code>BeanCreator</code> to be inserted, not null
      */
    public void addBeanCreator( ChainedBeanCreator beanCreator ) {
        beanCreators.add( beanCreator );
    }
    
    /** 
      * Clears the creator chain.
      */
    public void clearBeanCreators() {
        beanCreators.clear();
    }
     
    /** Worker class walks a chain */
    private class ChainWorker extends BeanCreationChain {
        /** Iterator for the creator list */
        private Iterator iterator;
        /** Creates the iterator */
        ChainWorker() {
            iterator = beanCreators.iterator();
        }
    
        /**
          * @see BeanCreationChain#create
          */
        public Object create( ElementMapping elementMapping, ReadContext readContext ) {
            if ( iterator.hasNext() ) {
                ChainedBeanCreator beanCreator = (ChainedBeanCreator) iterator.next();
                return beanCreator.create( elementMapping, readContext, this );
            }
            
            return null;
        }
    }
}