/*
 * Copyright 2002-2018 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
 *
 *      https://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.springframework.orm.hibernate5;

import org.hibernate.HibernateException;
import org.hibernate.Session;

import org.springframework.lang.Nullable;

/**
 * Callback interface for Hibernate code. To be used with {@link HibernateTemplate}'s
 * execution methods, often as anonymous classes within a method implementation.
 * A typical implementation will call {@code Session.load/find/update} to perform
 * some operations on persistent objects.
 *
 * @author Juergen Hoeller
 * @since 4.2
 * @param <T> the result type
 * @see HibernateTemplate
 * @see HibernateTransactionManager
 */
@FunctionalInterface
public interface HibernateCallback<T> {

	/**
	 * Gets called by {@code HibernateTemplate.execute} with an active
	 * Hibernate {@code Session}. Does not need to care about activating
	 * or closing the {@code Session}, or handling transactions.
	 * <p>Allows for returning a result object created within the callback,
	 * i.e. a domain object or a collection of domain objects.
	 * A thrown custom RuntimeException is treated as an application exception:
	 * It gets propagated to the caller of the template.
	 * @param session active Hibernate session
	 * @return a result object, or {@code null} if none
	 * @throws HibernateException if thrown by the Hibernate API
	 * @see HibernateTemplate#execute
	 */
	@Nullable
	T doInHibernate(Session session) throws HibernateException;

}
