001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *      http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.oozie.executor.jpa;
020
021import javax.persistence.EntityManager;
022
023/**
024 * Executor pattern interface that gives access to an {@link EntityManager}.
025 * <p>
026 * Implementations are executed by the {@link org.apache.oozie.service.JPAService}.
027 */
028public interface JPAExecutor<T> {
029
030    /**
031     * Return the name of the JPA executor. Used for logging and instrumentation.
032     *
033     * @return the name of the JPA executor.
034     */
035    String getName();
036
037    /**
038     * Method that encapsulates JPA access operations.
039     * <p>
040     * Implementations should not close the received {@link EntityManager}.
041     * <p>
042     * Implementations should commit any transaction before ending, else the transaction will be rolled back.
043     *
044     * @param em an active {@link EntityManager}
045     * @return a return value if any.
046     * @throws JPAExecutorException thrown if a jpa executor failed
047     */
048    T execute(EntityManager em) throws JPAExecutorException;
049
050}