【Spring实战】----Spring事务管理配置解析

上篇说了aop的配置，并且说了Spring事务管理是基于aop的，那么Spring声明式事务的配置就有两种方式：XML配置及注解配置

不多说，直接看配置文件

一、配置文件

applicationContext-transaction.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:aop="http://www.springframework.org/schema/aop" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd "><bean id="transactionManager" class="org.springframework.orm.hibernate5.HibernateTransactionManager"><property name="sessionFactory" ref="sessionFactory" /></bean><!-- 通知 --><tx:advice id="txAdvice" transaction-manager="transactionManager"><tx:attributes><!-- 传播行为 --><tx:method name="save*" propagation="REQUIRED"/><tx:method name="delete*" propagation="REQUIRED"/><tx:method name="insert*" propagation="REQUIRED"/><tx:method name="update*" propagation="REQUIRED"/><tx:method name="list*" propagation="SUPPORTS" read-only="true"/><tx:method name="get*" propagation="SUPPORTS" read-only="true"/></tx:attributes></tx:advice><!-- aop --><aop:config><aop:advisor advice-ref="txAdvice" pointcut="execution(* com.mango.jtt.service.*.*(..))"/></aop:config><!-- 注解管理事务 --><tx:annotation-driven transaction-manager="transactionManager"/></beans>

注解管理事务以上都是xml配置的事务，基于注解的事务，只需配置<tx:annotation-driven/>标签，然后在Spring bean中添加@Transational注解即可实现事务管理。

二，Spring事务管理本质

Spring并不直接管理事务，而是提供多种事务管理器，他们讲事务管理的职责委托给JAT或其他持久化机制所提供的平台相关的事务实现。上述配置文件中就是利用的Hibernate事务管理器实现的Hibernate事务管理。详细信息不说，想事务属性什么的，具体可参考spring in action及spring官方文档

三、继续说下事务对getCurrentSession的影响

在Spring实战篇系列----源码解析SessionFactory及Session的管理及getCurrentSession的使用文章中说了getCurrentSession是要基于事务的，才能实现session的生命周期的管理。那么Spring的事务管理到底做了什么。

首先看事务管理器HibernateTransactionManager，它并没有做太多工作，一个空的构造函数及

/** * Create a new HibernateTransactionManager instance. * A SessionFactory has to be set to be able to use it. * @see #setSessionFactory */public HibernateTransactionManager() {}

及afterPropertiesSet()方法

@Overridepublic void afterPropertiesSet() {if (getSessionFactory() == null) {throw new IllegalArgumentException("Property 'sessionFactory' is required");}if (this.entityInterceptor instanceof String && this.beanFactory == null) {throw new IllegalArgumentException("Property 'beanFactory' is required for 'entityInterceptorBeanName'");}// Check for SessionFactory's DataSource.if (this.autodetectDataSource && getDataSource() == null) {DataSource sfds = SessionFactoryUtils.getDataSource(getSessionFactory());if (sfds != null) {// Use the SessionFactory's DataSource for exposing transactions to JDBC code.if (logger.isInfoEnabled()) {logger.info("Using DataSource [" + sfds +"] of Hibernate SessionFactory for HibernateTransactionManager");}setDataSource(sfds);}}}

可见事务管理器的初始化并没有做太多工作。那么看事务管理对其的影响，先看调用栈

TransactionSynchronizationManager.initSynchronization() line: 269HibernateTransactionManager(AbstractPlatformTransactionManager).prepareSynchronization(DefaultTransactionStatus, TransactionDefinition) line: 542HibernateTransactionManager(AbstractPlatformTransactionManager).prepareTransactionStatus(TransactionDefinition, Object, boolean, boolean, boolean, Object) line: 513HibernateTransactionManager(AbstractPlatformTransactionManager).getTransaction(TransactionDefinition) line: 393TransactionInterceptor(TransactionAspectSupport).createTransactionIfNecessary(PlatformTransactionManager, TransactionAttribute, String) line: 426TransactionInterceptor(TransactionAspectSupport).invokeWithinTransaction(Method, Class<?>, InvocationCallback) line: 275TransactionInterceptor.invoke(MethodInvocation) line: 96ReflectiveMethodInvocation.proceed() line: 179ExposeInvocationInterceptor.invoke(MethodInvocation) line: 92ReflectiveMethodInvocation.proceed() line: 179JdkDynamicAopProxy.invoke(Object, Method, Object[]) line: 213$Proxy316.getOrderById(String) line: not availableOrderController.orderPay(String, Model) line: 84

从调用栈可以看出，只要在连接点处配置了事务管理，首先都会走到initSynchronization()。

/** * Activate transaction synchronization for the current thread. * Called by a transaction manager on transaction begin. * @throws IllegalStateException if synchronization is already active */public static void initSynchronization() throws IllegalStateException {if (isSynchronizationActive()) {throw new IllegalStateException("Cannot activate transaction synchronization - already active");}logger.trace("Initializing transaction synchronization");synchronizations.set(new LinkedHashSet<TransactionSynchronization>());}

最终会在synchronizations中set进new LinkedHashSet<TransactionSynchronization>()，从而isSynchronizationActive()为true

/** * Return if transaction synchronization is active for the current thread. * Can be called before register to avoid unnecessary instance creation. * @see #registerSynchronization */public static boolean isSynchronizationActive() {return (synchronizations.get() != null);}

因此这里也就解释了上上篇留下的疑问，为什么配置了事务管理，就不会抛异常了。其实只有配置了事务，session就会在事务提交或者回滚后关闭

SessionImpl.close() line: 402SessionFactoryUtils.closeSession(Session) line: 167SpringSessionSynchronization.afterCompletion(int) line: 138TransactionSynchronizationUtils.invokeAfterCompletion(List<TransactionSynchronization>, int) line: 168HibernateTransactionManager(AbstractPlatformTransactionManager).invokeAfterCompletion(List<TransactionSynchronization>, int) line: 1001HibernateTransactionManager(AbstractPlatformTransactionManager).triggerAfterCompletion(DefaultTransactionStatus, int) line: 976HibernateTransactionManager(AbstractPlatformTransactionManager).processCommit(DefaultTransactionStatus) line: 806HibernateTransactionManager(AbstractPlatformTransactionManager).commit(TransactionStatus) line: 730TransactionInterceptor(TransactionAspectSupport).commitTransactionAfterReturning(TransactionAspectSupport$TransactionInfo) line: 483TransactionInterceptor(TransactionAspectSupport).invokeWithinTransaction(Method, Class<?>, InvocationCallback) line: 290TransactionInterceptor.invoke(MethodInvocation) line: 96ReflectiveMethodInvocation.proceed() line: 179ExposeInvocationInterceptor.invoke(MethodInvocation) line: 92ReflectiveMethodInvocation.proceed() line: 179JdkDynamicAopProxy.invoke(Object, Method, Object[]) line: 213$Proxy316.getOrderById(String) line: not availableOrderController.orderPayInfo(String, Model) line: 72