在spring boot项目中，注解@SpringBootApplication在加载容器的时候，自动配置了事务管理器，所以不需要额外添加注解 @EnableTransactionManagement。仅仅在方法上加上 @Transactional 就能实现事务。




TransactionManager 创建


spring-boot-autoconfigure spring.factories  由自动配置创建



@AutoConfigureAfter({ 

        JtaAutoConfiguration.class, HibernateJpaAutoConfiguration.class,

        DataSourceTransactionManagerAutoConfiguration.class, Neo4jDataAutoConfiguration.class })

@EnableConfigurationProperties(TransactionProperties.class)

public class TransactionAutoConfiguration {}





@AutoConfigureOrder(Ordered.LOWEST_PRECEDENCE)

@EnableConfigurationProperties(DataSourceProperties.class)

class DataSourceTransactionManagerAutoConfiguration {

    @Bean

    @ConditionalOnMissingBean(PlatformTransactionManager.class)

    DataSourceTransactionManager transactionManager(DataSource dataSource,

            ObjectProvider transactionManagerCustomizers) {

        return new DataSourceTransactionManager(dataSource);  <=====        

    }

}



}







@Import({ JndiJtaConfiguration.class, BitronixJtaConfiguration.class, AtomikosJtaConfiguration.class })

public class JtaAutoConfiguration {}





Class AtomikosJtaConfiguration {  <== JtaAutoConfiguration import

    @Bean

    JtaTransactionManager transactionManager(

        UserTransaction userTransaction,           

        TransactionManager transactionManager,

        ObjectProvider transactionManagerCustomizers) {

      return new JtaTransactionManager(userTrans, transManager);  <====

    }

}