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springtransaction 事务
事务传播属性
@Transactional(propagation=Propagation.REQUIRED) //如果有事务,那么加入事务,没有的话新建一个(不写的情况下) **默认**
@Transactional(propagation=Propagation.NOT_SUPPORTED) //容器不为这个方法开启事务
@Transactional(propagation=Propagation.REQUIRES_NEW) //不管是否存在事务,都创建一个新的事务,原来的挂起,新的执行完毕,继续执行老的事务
@Transactional(propagation=Propagation.MANDATORY) //必须在一个已有的事务中执行,否则抛出异常
@Transactional(propagation=Propagation.NEVER) //必须在一个没有的事务中执行,否则抛出异常(与Propagation.MANDATORY相反)
@Transactional(propagation=Propagation.SUPPORTS) //如果其他bean调用这个方法,在其他bean中声明事务,那就用事务.如果其他bean没有声明事务,那就不用事务.
@Transactional(propagation=Propagation.NESTED) //如果当前存在事务，则在嵌套事务内执行。如果当前没有事务，则进行与PROPAGATION_REQUIRED类似的操作。
@Transactional (propagation = Propagation.REQUIRED,readOnly=true) //readOnly=true只读,不能更新,删除
@Transactional (propagation = Propagation.REQUIRED,timeout=30)//设置超时时间
@Transactional (propagation = Propagation.REQUIRED,isolation=Isolation.DEFAULT)//设置数据库隔离级别
xml配置：
<!-- hibernate事务管理器 -->
<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<!-- mybatis配置事务管理 -->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"></property>
</bean>
1.直接配置
<bean id="userDao"
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<!-- 配置事务管理器 -->
<property name="transactionManager" ref="transactionManager" />
<property name="target" ref="userDaoTarget" />
<property name="proxyInterfaces" value="com.absurd.xxxDao" />
<!-- 配置事务属性 -->
<property name="transactionAttributes">
<props>
<prop key="*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
2.共享一个代理基类
<bean id="transactionBase"
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"
lazy-init="true" abstract="true">
<!-- 配置事务管理器 -->
<property name="transactionManager" ref="transactionManager" />
<!-- 配置事务属性 -->
<property name="transactionAttributes">
<props>
<prop key="*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
<bean id="userDao" parent="transactionBase" >
<property name="target" ref="userDaoTarget" />
</bean>
<bean id="transactionInterceptor"
class="org.springframework.transaction.interceptor.TransactionInterceptor">
<property name="transactionManager" ref="transactionManager" />
<!-- 配置事务属性 -->
<property name="transactionAttributes">
<props>
<prop key="*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
<bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
<property name="beanNames">
<list>
<value>*Dao</value>
</list>
</property>
<property name="interceptorNames">
<list>
<value>transactionInterceptor</value>
</list>
</property>
</bean>
4.使用tx标签配置的拦截器
<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<tx:method name="*" propagation="REQUIRED" />
</tx:attributes>
</tx:advice>
<aop:config>
<aop:pointcut id="interceptorPointCuts"
expression="execution(* com.absurd.*.*(..))" />
<aop:advisor advice-ref="txAdvice"
pointcut-ref="interceptorPointCuts" />
</aop:config>
5.全注解
<tx:annotation-driven transaction-manager="transactionManager"/>
6.编程：
DefaultTransactionDefinition def = new DefaultTransactionDefinition();
def.setPropagationBehavior(TransactionDefinition.PROPAGATION_REQUIRED);
TransactionStatus status = txManager.getTransaction(def);
try {
userMapper.insertUser(user);
}
catch (MyException ex) {
txManager.rollback(status);
throw ex;
}
txManager.commit(status);
TransactionStatus
boolean isNewTransaction();
boolean hasSavepoint();
void setRollbackOnly();
boolean isRollbackOnly();
void flush();
boolean isCompleted();
PlatformTransactionManager
TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException;
void commit(TransactionStatus status) throws TransactionException;
void rollback(TransactionStatus status) throws TransactionException;
源码解析： 从TxNamespaceHandler入手
@Override
public void init() {
registerBeanDefinitionParser("advice", new TxAdviceBeanDefinitionParser());
registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
registerBeanDefinitionParser("jta-transaction-manager", new JtaTransactionManagerBeanDefinitionParser());
}
可以看到分别用不同的解析器去解析xml，
TxAdviceBeanDefinitionParser用来解析<tx:advice>并被解析为RuleBasedTransactionAttribute。
parse(Element element, ParserContext parserContext)->parseInternal(Element element, ParserContext parserContext)->getBeanClass(Element element)->TransactionInterceptor 解析到的bean被设置为TransactionInterceptor统一拦截
AnnotationDrivenBeanDefinitionParser是用来解析<annotation-driven>为RootBeanDefinition
DataSourceTransactionManager 和DataSourceTransactionManager
TransactionInterceptor
@Override
public Object invoke(final MethodInvocation invocation) throws Throwable {
// Work out the target class: may be {@code null}.
// The TransactionAttributeSource should be passed the target class
// as well as the method, which may be from an interface.
Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
// Adapt to TransactionAspectSupport's invokeWithinTransaction...
return invokeWithinTransaction(invocation.getMethod(), targetClass, new InvocationCallback() {
@Override
public Object proceedWithInvocation() throws Throwable {
return invocation.proceed();
}
});
}
protected Object invokeWithinTransaction(Method method, Class<?> targetClass, final InvocationCallback invocation)
throws Throwable {
// If the transaction attribute is null, the method is non-transactional.
final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(method, targetClass);
//选择事务管理器
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
//切面方法标识
final String joinpointIdentification = methodIdentification(method, targetClass);
if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
// Standard transaction demarcation with getTransaction and commit/rollback calls.
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
Object retVal = null;
try {
//原有逻辑执行
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// target invocation exception
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
//清理TransactionInfo信息
cleanupTransactionInfo(txInfo);
}
//提交事务
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
try {
Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr,
new TransactionCallback<Object>() {
@Override
public Object doInTransaction(TransactionStatus status) {
TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
try {
return invocation.proceedWithInvocation();
}
catch (Throwable ex) {
if (txAttr.rollbackOn(ex)) {
// A RuntimeException: will lead to a rollback.
if (ex instanceof RuntimeException) {
throw (RuntimeException) ex;
}
else {
throw new ThrowableHolderException(ex);
}
}
else {
// A normal return value: will lead to a commit.
return new ThrowableHolder(ex);
}
}
finally {
cleanupTransactionInfo(txInfo);
}
}
});
// Check result: It might indicate a Throwable to rethrow.
if (result instanceof ThrowableHolder) {
throw ((ThrowableHolder) result).getThrowable();
}
else {
return result;
}
}
catch (ThrowableHolderException ex) {
throw ex.getCause();
}
}
}
protected TransactionInfo createTransactionIfNecessary(
PlatformTransactionManager tm, TransactionAttribute txAttr, final String joinpointIdentification) {
// If no name specified, apply method identification as transaction name.
if (txAttr != null && txAttr.getName() == null) {
txAttr = new DelegatingTransactionAttribute(txAttr) {
@Override
public String getName() {
return joinpointIdentification;
}
};
}
TransactionStatus status = null;
if (txAttr != null) {
if (tm != null) {
//获取事务状态
status = tm.getTransaction(txAttr);
}
else {
//debug..
}
}
return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
}
接下来看下：AbstractPlatformTransactionManager#getTransaction
@Override
public final TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException {
Object transaction = doGetTransaction();
//...
//如果存在事务
if (isExistingTransaction(transaction)) {
return handleExistingTransaction(definition, transaction, debugEnabled);
}
// Check definition settings for new transaction.
if (definition.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) {
throw new InvalidTimeoutException("Invalid transaction timeout", definition.getTimeout());
}
//不存在事务，Propagation.MANDATORY，抛出异常
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
throw new IllegalTransactionStateException(
"No existing transaction found for transaction marked with propagation 'mandatory'");
}
//PROPAGATION_REQUIRED、PROPAGATION_REQUIRES_NEW、PROPAGATION_NESTED
else if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
//不用挂起
SuspendedResourcesHolder suspendedResources = suspend(null);
//debug...
}
try {
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
catch (RuntimeException ex) {
resume(null, suspendedResources);
throw ex;
}
catch (Error err) {
resume(null, suspendedResources);
throw err;
}
}
else {
//创建空事务，同步
if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT && logger.isWarnEnabled()) {
logger.warn("Custom isolation level specified but no actual transaction initiated; " +
"isolation level will effectively be ignored: " + definition);
}
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
return prepareTransactionStatus(definition, null, true, newSynchronization, debugEnabled, null);
}
}
private TransactionStatus handleExistingTransaction(
TransactionDefinition definition, Object transaction, boolean debugEnabled)
throws TransactionException {
//PROPAGATION_NEVER抛出异常(Propagation.NEVER)
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NEVER) {
throw new IllegalTransactionStateException(
"Existing transaction found for transaction marked with propagation 'never'");
}
//PROPAGATION_NOT_SUPPORTED不为这个方法开启事务（Propagation.NOT_SUPPORTED）
//线程存在事务则挂起（挂起实现其实就是断开连接下次进行重连）
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NOT_SUPPORTED) {
//debug...
Object suspendedResources = suspend(transaction);
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
//创建非事务的事务状态，让方法非事务地执行
return prepareTransactionStatus(
definition, null, false, newSynchronization, debugEnabled, suspendedResources);
}
//PROPAGATION_REQUIRES_NEW不管是否存在事务,都创建一个新的事务,原来的挂起,新的执行完毕,继续执行老的事务(Propagation.REQUIRES_NEW )
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW) {
//...
//挂起原来事务
SuspendedResourcesHolder suspendedResources = suspend(transaction);
try {
//只要不是never就执行完毕新的
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
catch (RuntimeException beginEx) {
//异常了恢复原来事务
resumeAfterBeginException(transaction, suspendedResources, beginEx);
throw beginEx;
}
catch (Error beginErr) {
resumeAfterBeginException(transaction, suspendedResources, beginErr);
throw beginErr;
}
}
//NESTED如果是嵌套事务（TransactionDefinition.PROPAGATION_NESTED）
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
//如果不允许事务嵌套，则抛出异常
if (!isNestedTransactionAllowed()) {
throw new NestedTransactionNotSupportedException(
"Transaction manager does not allow nested transactions by default - " +"specify 'nestedTransactionAllowed' property with value 'true'");
}
//debug...
}
//如果允许使用savepoint保存点保存嵌套事务
if (useSavepointForNestedTransaction()) {
//为当前事务创建一个保存点
DefaultTransactionStatus status =
prepareTransactionStatus(definition, transaction, false, false, debugEnabled, null);
status.createAndHoldSavepoint();
return status;
}
else {
//如果不允许使用savepoint保存点保存嵌套事务 ,使用JTA的嵌套commit/rollback调用
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, null);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
}
//debug...
//PROPAGATION_SUPPORTS or PROPAGATION_REQUIRED.
//校验已存在的事务，如果已有事务与事务属性配置不一致，则抛出异常
if (isValidateExistingTransaction()) {
//如果事务隔离级别不是默认隔离级别 ，获取到的当前事务隔离级别为null 或 获取不等于事务属性配置的隔离级别
if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) {
Integer currentIsolationLevel = TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
if (currentIsolationLevel == null || currentIsolationLevel != definition.getIsolationLevel()) {
Constants isoConstants = DefaultTransactionDefinition.constants;
throw new IllegalTransactionStateException("Participating transaction with definition [" +
definition + "] specifies isolation level which is incompatible with existing transaction: " +
(currentIsolationLevel != null ?
isoConstants.toCode(currentIsolationLevel, DefaultTransactionDefinition.PREFIX_ISOLATION) :
"(unknown)"));
}
}
//如果当前已有事务是只读 ，抛出异常
if (!definition.isReadOnly()) {
if (TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
throw new IllegalTransactionStateException("Participating transaction with definition [" +
definition + "] is not marked as read-only but existing transaction is");
}
}
}
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
return prepareTransactionStatus(definition, transaction, false, newSynchronization, debugEnabled, null);
}
@Override
protected void doBegin(Object transaction, TransactionDefinition definition) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
Connection con = null;
try {
if (txObject.getConnectionHolder() == null ||
txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
Connection newCon = this.dataSource.getConnection();
//debug...
}
txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
}
txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
con = txObject.getConnectionHolder().getConnection();
Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
txObject.setPreviousIsolationLevel(previousIsolationLevel);
if (con.getAutoCommit()) {
txObject.setMustRestoreAutoCommit(true);
//debug...
con.setAutoCommit(false);
}
txObject.getConnectionHolder().setTransactionActive(true);
int timeout = determineTimeout(definition);
if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
}
// Bind the session holder to the thread.
if (txObject.isNewConnectionHolder()) {
TransactionSynchronizationManager.bindResource(getDataSource(), txObject.getConnectionHolder());
}
}
catch (Throwable ex) {
if (txObject.isNewConnectionHolder()) {
DataSourceUtils.releaseConnection(con, this.dataSource);
txObject.setConnectionHolder(null, false);
}
throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
}
}
protected final SuspendedResourcesHolder suspend(Object transaction) throws TransactionException {
//如果事务是激活的，且当前线程事务同步机制也是激活状态
if (TransactionSynchronizationManager.isSynchronizationActive()) {
//挂起当前线程中所有同步的事务 TransactionSynchronization#suspend 还有 TransactionSynchronizationManager#unbindResource
List<TransactionSynchronization> suspendedSynchronizations = doSuspendSynchronization();
try {
Object suspendedResources = null;
if (transaction != null) {
suspendedResources = doSuspend(transaction);
}
String name = TransactionSynchronizationManager.getCurrentTransactionName();
TransactionSynchronizationManager.setCurrentTransactionName(null);
boolean readOnly = TransactionSynchronizationManager.isCurrentTransactionReadOnly();
TransactionSynchronizationManager.setCurrentTransactionReadOnly(false);
Integer isolationLevel = TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(null);
boolean wasActive = TransactionSynchronizationManager.isActualTransactionActive();
TransactionSynchronizationManager.setActualTransactionActive(false);
return new SuspendedResourcesHolder(
suspendedResources, suspendedSynchronizations, name, readOnly, isolationLevel, wasActive);
}
catch (RuntimeException ex) {
// doSuspend failed - original transaction is still active...
doResumeSynchronization(suspendedSynchronizations);
throw ex;
}
catch (Error err) {
// doSuspend failed - original transaction is still active...
doResumeSynchronization(suspendedSynchronizations);
throw err;
}
}
else if (transaction != null) {
// Transaction active but no synchronization active.
Object suspendedResources = doSuspend(transaction);
return new SuspendedResourcesHolder(suspendedResources);
}
else {
// Neither transaction nor synchronization active.
return null;
}
}
//doSuspendSynchronization方法将逐个挂起当前线程中的TransactionSynchronization
private List<TransactionSynchronization> doSuspendSynchronization() {
List<TransactionSynchronization> suspendedSynchronizations =
TransactionSynchronizationManager.getSynchronizations();
for (TransactionSynchronization synchronization : suspendedSynchronizations) {
synchronization.suspend();
}
TransactionSynchronizationManager.clearSynchronization();
return suspendedSynchronizations;
}
//ConnectionSynchronization#suspend
public void suspend() {
if (this.holderActive) {
//解绑数据源
TransactionSynchronizationManager.unbindResource(this.dataSource);
// 如果存在连接，且处于打开状态
if (this.connectionHolder.hasConnection() && !this.connectionHolder.isOpen()) {
// 当挂起的时候如果没有句柄连接到该connection，将释放该连接
// 当resume的时候 会重开打开一个连接参与到原来的事务中
releaseConnection(this.connectionHolder.getConnection(), this.dataSource);
this.connectionHolder.setConnection(null);
}
}
}
//恢复事务
private void doResumeSynchronization(List<TransactionSynchronization> suspendedSynchronizations) {
TransactionSynchronizationManager.initSynchronization();
for (TransactionSynchronization synchronization : suspendedSynchronizations) {
synchronization.resume();
TransactionSynchronizationManager.registerSynchronization(synchronization);
}
}
//SqlSessionSynchronization#resume
@Override
public void resume() {
if (this.holderActive) {
//debug...
TransactionSynchronizationManager.bindResource(this.sessionFactory, this.holder);
}
}
//DataSourceTransactionManager#doSuspend
@Override
protected Object doSuspend(Object transaction) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
txObject.setConnectionHolder(null);
ConnectionHolder conHolder = (ConnectionHolder)
TransactionSynchronizationManager.unbindResource(this.dataSource);
return conHolder;
}
事务提交
AbstractPlatformTransactionManager##commit
@Override
public final void commit(TransactionStatus status) throws TransactionException {
//如果事务状态是已完成，再次提交会抛出“Transaction is already completed - do not call commit or rollback more than once per transaction”
if (status.isCompleted()) {
throw new IllegalTransactionStateException(
"Transaction is already completed - do not call commit or rollback more than once per transaction");
}
DefaultTransactionStatus defStatus = (DefaultTransactionStatus) status;
//rollback only
if (defStatus.isLocalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Transactional code has requested rollback");
}
//回滚
processRollback(defStatus);
return;
}
if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
}
processRollback(defStatus);
// Throw UnexpectedRollbackException only at outermost transaction boundary
// or if explicitly asked to.
if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
throw new UnexpectedRollbackException(
"Transaction rolled back because it has been marked as rollback-only");
}
return;
}
processCommit(defStatus);
}
private void processRollback(DefaultTransactionStatus status) {
try {
try {
//回调TransactionSynchronization对象的beforeCompletion方法。
triggerBeforeCompletion(status);
//有保存点
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Rolling back transaction to savepoint");
}
//回滚到保存点
status.rollbackToHeldSavepoint();
}
//如果是一个新事务
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction rollback");
}
//rollback
doRollback(status);
}
else if (status.hasTransaction()) {
//如果RollbackOnly或者globalRollbackOnParticipationFailure（部分失败）
if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
if (status.isDebug()) {
logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
}
doSetRollbackOnly(status);
}
else {
if (status.isDebug()) {
logger.debug("Participating transaction failed - letting transaction originator decide on rollback");
}
}
}
else {
logger.debug("Should roll back transaction but cannot - no transaction available");
}
}
catch (RuntimeException ex) {
//TransactionSynchronization 的afterCompletion
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
throw ex;
}
catch (Error err) {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
throw err;
}
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
}
finally {
cleanupAfterCompletion(status);
}
}
private void processCommit(DefaultTransactionStatus status) throws TransactionException {
try {
boolean beforeCompletionInvoked = false;
try {
prepareForCommit(status);
//TransactionSynchronization 的beforeCommit 提交前提示
triggerBeforeCommit(status);
//TransactionSynchronization 的beforeCompletion 完成前提示
triggerBeforeCompletion(status);
beforeCompletionInvoked = true;
boolean globalRollbackOnly = false;
if (status.isNewTransaction() || isFailEarlyOnGlobalRollbackOnly()) {
globalRollbackOnly = status.isGlobalRollbackOnly();
}
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Releasing transaction savepoint");
}
status.releaseHeldSavepoint();
}
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction commit");
}
//提交事务
doCommit(status);
}
// Throw UnexpectedRollbackException if we have a global rollback-only
// marker but still didn't get a corresponding exception from commit.
if (globalRollbackOnly) {
throw new UnexpectedRollbackException(
"Transaction silently rolled back because it has been marked as rollback-only");
}
}
catch (UnexpectedRollbackException ex) {
// can only be caused by doCommit
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
throw ex;
}
catch (TransactionException ex) {
// can only be caused by doCommit
if (isRollbackOnCommitFailure()) {
doRollbackOnCommitException(status, ex);
}
else {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
}
throw ex;
}
catch (RuntimeException ex) {
if (!beforeCompletionInvoked) {
triggerBeforeCompletion(status);
}
doRollbackOnCommitException(status, ex);
throw ex;
}
catch (Error err) {
if (!beforeCompletionInvoked) {
triggerBeforeCompletion(status);
}
doRollbackOnCommitException(status, err);
throw err;
}
// Trigger afterCommit callbacks, with an exception thrown there
// propagated to callers but the transaction still considered as committed.
try {
triggerAfterCommit(status);
}
finally {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_COMMITTED);
}
}
finally {
cleanupAfterCompletion(status);
}
}
隔离级别（其实最后是通过jdbc的隔离级别做的）：
Isolation.DEFAULT(TransactionDefinition.ISOLATION_DEFAULT) 使用数据库默认的事务隔离级别。
Isolation.READ_UNCOMMITTED(TransactionDefinition.ISOLATION_READ_UNCOMMITTED), 这是事务最低的隔离级别，它允许另外一个事务可以看到这个事务未提交的数据。这种隔离级别会产生脏读，不可重复读和幻像读。 实现：
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
Isolation.READ_COMMITTED(TransactionDefinition.ISOLATION_READ_COMMITTED), 保证一个事务修改的数据提交后才能被另外一个事务读取。另外一个事务不能读取该事务未提交的数据。这种事务隔离级别可以避免脏读出现，但是可能会出现不可重复读和幻像读。 实现：
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED
Isolation.REPEATABLE_READ(TransactionDefinition.ISOLATION_REPEATABLE_READ), 这种事务隔离级别可以防止脏读，不可重复读。但是可能出现幻像读。 实现：
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ
Isolation.SERIALIZABLE(TransactionDefinition.ISOLATION_SERIALIZABLE); 这是花费最高代价但是最可靠的事务隔离级别。事务被处理为顺序执行。除了防止脏读，不可重复读外，还避免了幻读。 实现：
SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE
详细：http://www1350.github.io/#post/64
