001/*
002 * Copyright 2002-2020 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.TransactionManager;
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 {@code PlatformTransactionManager} bean
025 * (or {@code ReactiveTransactionManager} bean) to be used for annotation-driven
026 * transaction management, as opposed to the default approach of a by-type lookup.
027 * One reason this might be necessary is if there are two {@code PlatformTransactionManager}
028 * beans (or two {@code ReactiveTransactionManager} beans) present in the container.
029 *
030 * <p>See @{@link EnableTransactionManagement} for general examples and context;
031 * see {@link #annotationDrivenTransactionManager()} for detailed instructions.
032 *
033 * <p>Note that in by-type lookup disambiguation cases, an alternative approach to
034 * implementing this interface is to simply mark one of the offending
035 * {@code PlatformTransactionManager} {@code @Bean} methods (or
036 * {@code ReactiveTransactionManager} {@code @Bean} methods) as
037 * {@link org.springframework.context.annotation.Primary @Primary}.
038 * This is even generally preferred since it doesn't lead to early initialization
039 * of the {@code TransactionManager} bean.
040 *
041 * @author Chris Beams
042 * @since 3.1
043 * @see EnableTransactionManagement
044 * @see org.springframework.context.annotation.Primary
045 * @see org.springframework.transaction.PlatformTransactionManager
046 * @see org.springframework.transaction.ReactiveTransactionManager
047 */
048public interface TransactionManagementConfigurer {
049
050        /**
051         * Return the default transaction manager bean to use for annotation-driven database
052         * transaction management, i.e. when processing {@code @Transactional} methods.
053         * <p>There are two basic approaches to implementing this method:
054         * <h3>1. Implement the method and annotate it with {@code @Bean}</h3>
055         * In this case, the implementing {@code @Configuration} class implements this method,
056         * marks it with {@code @Bean}, and configures and returns the transaction manager
057         * directly within the method body:
058         * <pre class="code">
059         * &#064;Bean
060         * &#064;Override
061         * public PlatformTransactionManager annotationDrivenTransactionManager() {
062         *     return new DataSourceTransactionManager(dataSource());
063         * }</pre>
064         * <h3>2. Implement the method without {@code @Bean} and delegate to another existing
065         * {@code @Bean} method</h3>
066         * <pre class="code">
067         * &#064;Bean
068         * public PlatformTransactionManager txManager() {
069         *     return new DataSourceTransactionManager(dataSource());
070         * }
071         *
072         * &#064;Override
073         * public PlatformTransactionManager annotationDrivenTransactionManager() {
074         *     return txManager(); // reference the existing {@code @Bean} method above
075         * }</pre>
076         * If taking approach #2, be sure that <em>only one</em> of the methods is marked
077         * with {@code @Bean}!
078         * <p>In either scenario #1 or #2, it is important that the
079         * {@code PlatformTransactionManager} instance is managed as a Spring bean within the
080         * container since most {@code PlatformTransactionManager} implementations take advantage
081         * of Spring lifecycle callbacks such as {@code InitializingBean} and
082         * {@code BeanFactoryAware}. Note that the same guidelines apply to
083         * {@code ReactiveTransactionManager} beans.
084         * @return a {@link org.springframework.transaction.PlatformTransactionManager} or
085         * {@link org.springframework.transaction.ReactiveTransactionManager} implementation
086         */
087        TransactionManager annotationDrivenTransactionManager();
088
089}