Injectors.java

package org.sigmah.server.inject.util;

/*
 * #%L
 * Sigmah
 * %%
 * Copyright (C) 2010 - 2016 URD
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import java.lang.reflect.ParameterizedType;

/**
 * Utility class providing static methods for injectors.
 * 
 * @author Denis Colliot (dcolliot@ideia.fr)
 */
public final class Injectors {

	private Injectors() {
		// Only provides static methods.
	}

	/**
	 * Classes enhanced by <b>guice</b> injector possess this tag into wrapped class name.
	 */
	private static final String GUICE_ENHANCED_CLASS_TAG = "EnhancerByGuice";

	/**
	 * <p>
	 * Returns the given object {@code instance} corresponding <em>original</em> class.
	 * </p>
	 * <p>
	 * Classes using {@link com.google.inject.persist.Transactional} annotation are automatically enhanced by <b>guice</b>
	 * injector. This method retrieves the <em>original</em> class (if necessary).
	 * </p>
	 * 
	 * @param instance
	 *          An object instance which <em>original</em> class is returned.
	 * @return the given object {@code instance} corresponding <em>original</em> class.
	 */
	@SuppressWarnings("unchecked")
	public static <T> Class<? extends T> getClass(final T instance) {

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

		Class<?> result = instance.getClass();
		while (result.getSimpleName().contains(GUICE_ENHANCED_CLASS_TAG)) {
			// Implementations with @Transactional annotation are wrapped by Guice.
			result = result.getSuperclass();
		}

		return (Class<T>) result;
	}

	/**
	 * Recursive method finding the given {@code clazz} first super generic class with parameterized type.
	 * 
	 * @param clazz
	 *          The source class.
	 * @return the given {@code clazz} first super generic class parameterized type.
	 */
	public static ParameterizedType findGenericSuperClass(final Class<?> clazz) {
		if (!(clazz.getGenericSuperclass() instanceof ParameterizedType)) {
			return findGenericSuperClass(clazz.getSuperclass());
		}
		return (ParameterizedType) clazz.getGenericSuperclass();
	}

}