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 */
018package org.apache.oozie.executor.jpa;
019
020import javax.persistence.EntityManager;
021
022/**
023 * Executor pattern interface that gives access to an {@link EntityManager}.
024 * <p/>
025 * Implementations are executed by the {@link org.apache.oozie.service.JPAService}.
026 */
027public interface JPAExecutor<T> {
028
029    /**
030     * Return the name of the JPA executor. Used for logging and instrumentation.
031     *
032     * @return the name of the JPA executor.
033     */
034    public String getName();
035
036    /**
037     * Method that encapsulates JPA access operations.
038     * <p/>
039     * Implementations should not close the received {@link EntityManager}.
040     * <p/>
041     * Implementations should commit any transaction before ending, else the transaction will be rolled back.
042     *
043     * @param em an active {@link EntityManager}
044     * @return a return value if any.
045     * @throws JPAExecutorException thrown if a jpa executor failed
046     */
047    public T execute(EntityManager em) throws JPAExecutorException;
048
049}