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    package org.apache.oozie.executor.jpa;
019    
020    import 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     */
027    public 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    }