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JSefa (Java Simple exchange format api) is a simple library for stream-based serialization of java objects to XML, CSV, FLR or any other format and back again using an iterator-style interface independent of the serialization format. The mapping between java object types and types of the serialization format (e. g. xml complex element types) can be defined either by annotating the java classes or programmatically using a simple API. The current implementation supports XML, CSV and FLR - for XML it is based on JSR 173.

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/*
 * Copyright 2007 the original author or authors.
 *
 * 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 net.sf.jsefa.common.accessor;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * The abstract base class for implementations of {@link ObjectAccessorProvider}.
 * 
 * @author Norman Lahme-Huetig
 * 
 */
public abstract class AbstractObjectAccessorProvider implements ObjectAccessorProvider {

    private final ConcurrentMap, ObjectAccessor> objectAccessors;

    /**
     * Constructs a new AbstractObjectAccessorProvider.
     */
    protected AbstractObjectAccessorProvider() {
        this.objectAccessors = new ConcurrentHashMap, ObjectAccessor>();
    }
    
    /**
     * {@inheritDoc}
     */
    public ObjectAccessor get(Class objectType) {
        Class aClass = objectType;
        if (objectType.isInterface()) {
            aClass = getImplementor(aClass);
        }
        if (aClass == null) {
            return null;
        }
        ObjectAccessor objectAccessor = this.objectAccessors.get(aClass);
        if (objectAccessor == null) {
            synchronized (this) {
                objectAccessor = create(aClass);
                this.objectAccessors.put(aClass, objectAccessor);
            }
        }
        return objectAccessor;
    }
    
    /**
     * Creates an ObjectAccessor for the given object type.
     * @param objectType the object type
     * @return an object accessor
     */
    protected abstract ObjectAccessor create(Class objectType);


    /**
     * Returns an implementation for the given interface.
     * 
     * @param anInterface the interface
     * @return a class implementing the given interface or null.
     */
    private Class getImplementor(Class anInterface) {
        if (List.class.isAssignableFrom(anInterface)) {
            return ArrayList.class;
        }
        if (Set.class.isAssignableFrom(anInterface)) {
            return HashSet.class;
        }
        if (Queue.class.isAssignableFrom(anInterface)) {
            return LinkedList.class;
        }
        if (Map.class.isAssignableFrom(anInterface)) {
            return HashMap.class;
        }
        return null;
    }

}