001    // Copyright 2007, 2008 The Apache Software Foundation
002    //
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.
014    
015    package org.tynamo.jpa;
016    
017    import javax.persistence.EntityManager;
018    
019    /**
020     * Manages the JPA transaction for the current thread. This includes creating an entity manager as
021     * needed, allowing the em to checkpoint (commit the current transaction and continue) and commit
022     * the transaction automatically at the end of the request.
023     * <p/>
024     * Remember that in Tapestry, action requests and render requests are entirely separate, and you
025     * will see a separate request and a separate transaction for each. Care should be taken to ensure
026     * that entity objects that are retained (in the session, as persistent field values) between
027     * requests are handled correctly (they tend to become detached instances).
028     * <p/>
029     * This implementation of this service is per-thread.
030     */
031    public interface JPATransactionManager
032    {
033            /**
034             * Gets the active session for this request, creating it as necessary. When the session is first
035             * created, a transaction is started.
036             * 
037             * @return the request's entityManager
038             * @see JPAEntityManagerSource
039             */
040            EntityManager getEntityManager();
041    
042            /**
043             * Commits the current transaction (which will cause a flush of data to the database), then
044             * starts a new transaction to replace it.
045             */
046            void commit();
047    
048            /**
049             * Aborts the current transaction, and starts a new transaction to replace it.
050             */
051            void abort();
052    }