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Cayenne Object Persistence Framework
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/* ====================================================================
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any,
 *    must include the following acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many
 * individuals and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * .
 */
package org.objectstyle.cayenne.map;

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

import org.objectstyle.cayenne.property.ClassDescriptor;
import org.objectstyle.cayenne.property.ClassDescriptorFactory;

/**
 * A caching descriptor factory that creates ClassDescriptors based on Cayenne mapping
 * information.
 * 
 * Synchronization note: This implementation is NOT synchronized, and requires external
 * synchronization if used in a multi-threaded environment.
 * 
 * 
 * @since 1.2
 * @author Andrus Adamchik
 */
public class EntityDescriptorFactory implements ClassDescriptorFactory {

    protected EntityResolver resolver;
    protected Map classDescriptors;

    public EntityDescriptorFactory(EntityResolver resolver) {
        this.resolver = resolver;
    }

    public ClassDescriptor getDescriptor(String entityName) {

        if (classDescriptors == null) {
            classDescriptors = new HashMap();
        }
        else {

            ClassDescriptor descriptor = (ClassDescriptor) classDescriptors
                    .get(entityName);
            if (descriptor != null) {
                return descriptor;
            }
        }

        EntityDescriptor entityDescriptor = createDescriptor(entityName);

        if (entityDescriptor == null) {
            return null;
        }

        classDescriptors.put(entityName, entityDescriptor);

        // compile after caching to avoid infinite loops during ArcProperty compilation
        entityDescriptor.compile(resolver);
        return entityDescriptor;
    }

    /**
     * Creates a new descriptor that is not compiled. Compilation is intentionally
     * deferred until after the descriptor is cached, as it triggers creation of related
     * entity descriptors and may result in an endless loop.
     */
    protected EntityDescriptor createDescriptor(String entityName) {
        ObjEntity entity = resolver.getObjEntity(entityName);
        if (entity == null) {
            return null;
        }

        String superEntityName = entity.getSuperEntityName();

        ClassDescriptor superDescriptor = (superEntityName != null) ? resolver
                .getClassDescriptor(superEntityName) : null;

        // return uncompiled
        return new EntityDescriptor(entity, superDescriptor);
    }
}