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/* Copyright 2013 David Wolverton
 * 
 * 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 com.googlecode.genericdao.search.hibernate;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import org.hibernate.HibernateException;
import org.hibernate.PropertyNotFoundException;
import org.hibernate.SessionFactory;
import org.hibernate.metadata.ClassMetadata;
import org.hibernate.proxy.HibernateProxyHelper;

import com.googlecode.genericdao.search.Metadata;
import com.googlecode.genericdao.search.MetadataUtil;

/**
 * Implementation of MetadataUtil for Hibernate
 * 
 * A singleton instance of this class is maintained for each SessionFactory.
 * This should be accessed using
 * {@link HibernateMetadataUtil#getInstanceForSessionFactory(SessionFactory)}.
 * 
 * @author dwolverton
 */
public class HibernateMetadataUtil implements MetadataUtil {

	private static Map map = new HashMap();

	public static HibernateMetadataUtil getInstanceForSessionFactory(SessionFactory sessionFactory) {
		HibernateMetadataUtil instance = map.get(sessionFactory);
		if (instance == null) {
			instance = new HibernateMetadataUtil();
			instance.sessionFactory = sessionFactory;
			map.put(sessionFactory, instance);
		}
		return instance;
	}

	private SessionFactory sessionFactory;

	protected HibernateMetadataUtil() {
	}

	// --- Public Methods ---

	public Serializable getId(Object entity) {
		if (entity == null)
			throw new NullPointerException("Cannot get ID from null object.");
		return get(entity.getClass()).getIdValue(entity);
	}
	
	public boolean isId(Class rootClass, String propertyPath) {
		if (propertyPath == null || "".equals(propertyPath))
			return false;
		// with hibernate, "id" always refers to the id property, no matter what
		// that property is named. just make sure the segment before this "id"
		// refers to an entity since only entities have ids.
		if (propertyPath.equals("id")
				|| (propertyPath.endsWith(".id") && get(rootClass, propertyPath.substring(0, propertyPath.length() - 3))
						.isEntity()))
			return true;

		// see if the property is the identifier property of the entity it
		// belongs to.
		int pos = propertyPath.lastIndexOf(".");
		if (pos != -1) {
			Metadata parentType = get(rootClass, propertyPath.substring(0, pos));
			if (!parentType.isEntity())
				return false;
			return propertyPath.substring(pos + 1).equals(parentType.getIdProperty());
		} else {
			return propertyPath.equals(sessionFactory.getClassMetadata(rootClass).getIdentifierPropertyName());
		}
	}

	public Metadata get(Class entityClass) throws IllegalArgumentException {
		entityClass = getUnproxiedClass(entityClass);
		ClassMetadata cm = sessionFactory.getClassMetadata(entityClass);
		if (cm == null) {
			throw new IllegalArgumentException("Unable to introspect " + entityClass.toString()
					+ ". The class is not a registered Hibernate entity.");
		} else {
			return new HibernateEntityMetadata(sessionFactory, cm, null);
		}
	}

	public Metadata get(Class rootEntityClass, String propertyPath) throws IllegalArgumentException {
		try {
			Metadata md = get(rootEntityClass);
			if (propertyPath == null || "".equals(propertyPath))
				return md;

			String[] chain = propertyPath.split("\\.");

			for (int i = 0; i < chain.length; i++) {
				md = md.getPropertyType(chain[i]);
			}

			return md;

		} catch (HibernateException ex) {
			throw new IllegalArgumentException("Could not find property '" + propertyPath + "' on class "
					+ rootEntityClass + ".");
		}
	}
	
	public  Class getUnproxiedClass(Class klass) {
		//cm will be null if entityClass is not registered with Hibernate or when
		//it is a Hibernate proxy class (e.x. test.googlecode.genericdao.model.Person_$$_javassist_5).
		//So if a class is not recognized, we will look at superclasses to see if
		//it is a proxy.
		while (sessionFactory.getClassMetadata(klass) == null) {
			klass = klass.getSuperclass();
			if (Object.class.equals(klass))
				return null;
		}
		
		return (Class) klass;
	}
	
	public  Class getUnproxiedClass(Object entity) {
		return HibernateProxyHelper.getClassWithoutInitializingProxy(entity);
	}
}