001/*
002 * Copyright 2002-2016 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.transaction.annotation;
018
019import org.springframework.transaction.PlatformTransactionManager;
020
021/**
022 * Interface to be implemented by @{@link org.springframework.context.annotation.Configuration
023 * Configuration} classes annotated with @{@link EnableTransactionManagement} that wish to
024 * or need to explicitly specify the default {@link PlatformTransactionManager} bean to be
025 * used for annotation-driven transaction management, as opposed to the default approach
026 * of a by-type lookup. One reason this might be necessary is if there are two
027 * {@code PlatformTransactionManager} beans present in the container.
028 *
029 * <p>See @{@link EnableTransactionManagement} for general examples and context;
030 * see {@link #annotationDrivenTransactionManager()} for detailed instructions.
031 *
032 * <p>Note that in by-type lookup disambiguation cases, an alternative approach to
033 * implementing this interface is to simply mark one of the offending
034 * {@code PlatformTransactionManager} {@code @Bean} methods as
035 * {@link org.springframework.context.annotation.Primary @Primary}.
036 * This is even generally preferred since it doesn't lead to early initialization
037 * of the {@code PlatformTransactionManager} bean.
038 *
039 * @author Chris Beams
040 * @since 3.1
041 * @see EnableTransactionManagement
042 * @see org.springframework.context.annotation.Primary
043 */
044public interface TransactionManagementConfigurer {
045
046        /**
047         * Return the default transaction manager bean to use for annotation-driven database
048         * transaction management, i.e. when processing {@code @Transactional} methods.
049         * <p>There are two basic approaches to implementing this method:
050         * <h3>1. Implement the method and annotate it with {@code @Bean}</h3>
051         * In this case, the implementing {@code @Configuration} class implements this method,
052         * marks it with {@code @Bean} and configures and returns the transaction manager
053         * directly within the method body:
054         * <pre class="code">
055         * &#064;Bean
056         * &#064;Override
057         * public PlatformTransactionManager annotationDrivenTransactionManager() {
058         *     return new DataSourceTransactionManager(dataSource());
059         * }</pre>
060         * <h3>2. Implement the method without {@code @Bean} and delegate to another existing
061         * {@code @Bean} method</h3>
062         * <pre class="code">
063         * &#064;Bean
064         * public PlatformTransactionManager txManager() {
065         *     return new DataSourceTransactionManager(dataSource());
066         * }
067         *
068         * &#064;Override
069         * public PlatformTransactionManager annotationDrivenTransactionManager() {
070         *     return txManager(); // reference the existing {@code @Bean} method above
071         * }</pre>
072         * If taking approach #2, be sure that <em>only one</em> of the methods is marked
073         * with {@code @Bean}!
074         * <p>In either scenario #1 or #2, it is important that the
075         * {@code PlatformTransactionManager} instance is managed as a Spring bean within the
076         * container as all {@code PlatformTransactionManager} implementations take advantage
077         * of Spring lifecycle callbacks such as {@code InitializingBean} and
078         * {@code BeanFactoryAware}.
079         */
080        PlatformTransactionManager annotationDrivenTransactionManager();
081
082}