001    /**
002     * Copyright (c) 2010 Yahoo! Inc. All rights reserved.
003     * Licensed under the Apache License, Version 2.0 (the "License");
004     * you may not use this file except in compliance with the License.
005     * You may obtain a copy of the License at
006     *
007     *   http://www.apache.org/licenses/LICENSE-2.0
008     *
009     *  Unless required by applicable law or agreed to in writing, software
010     *  distributed under the License is distributed on an "AS IS" BASIS,
011     *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012     *  See the License for the specific language governing permissions and
013     *  limitations under the License. See accompanying LICENSE file.
014     */
015    package org.apache.oozie.executor.jpa;
016    
017    import javax.persistence.EntityManager;
018    
019    /**
020     * Executor pattern interface that gives access to an {@link EntityManager}.
021     * <p/>
022     * Implementations are executed by the {@link org.apache.oozie.service.JPAService}.
023     */
024    public interface JPAExecutor<T> {
025    
026        /**
027         * Return the name of the JPA executor. Used for logging and instrumentation.
028         *
029         * @return the name of the JPA executor.
030         */
031        public String getName();
032    
033        /**
034         * Method that encapsulates JPA access operations.
035         * <p/>
036         * Implementations should not close the received {@link EntityManager}.
037         * <p/>
038         * Implementations should commit any transaction before ending, else the transaction will be rolled back.
039         *
040         * @param em an active {@link EntityManager}
041         * @return a return value if any.
042         * @throws JPAExecutorException thrown if a jpa executor failed
043         */
044        public T execute(EntityManager em) throws JPAExecutorException;
045    
046    }