在上一篇文章Spring源码解析之Spring事务源码解析(一)@EnableTransactionManagement注解解析中，我们阅读了Spring事务功能的注解@EnableTransactionManagement的实现逻辑
在进行接下来的源码解析之前首先来简单了解一下
传统的jdbc应用事务操作
- 开启事务
- save、update、delete等操作
- 出现异常进行回滚
- 正常情况提交事务
Spring事务管理
Spring事务实现是基于@Transactional注解的SpringAOP实现，在接着往下阅读本篇文章的时候希望您对于 SpringAOP的源码有一定的了解，如果不了解可以参考如下文章：
基于注解的SpringAOP源码解析（一）
基于注解的SpringAOP源码解析（二）
获取增强
在阅读完AOP的原理之后，我们知道，当一个bean实例化之后会尝试获取所有适用于此Bean的增强。而在上篇文章中，我们已经发现了，@EnableTransactionManagement注解会往Spring中注入一个增强BeanFactoryTransactionAttributeSourceAdvisor。经过一番代码调用以后，会进入这么一个方法，这里的第一个入参就是BeanFactoryTransactionAttributeSourceAdvisor增强
public static boolean canApply(Advisor advisor, Class targetClass, boolean hasIntroductions) {
if (advisor instanceof IntroductionAdvisor) {
return ((IntroductionAdvisor) advisor).getClassFilter().matches(targetClass);
}
else if (advisor instanceof PointcutAdvisor) {
PointcutAdvisor pca = (PointcutAdvisor) advisor;
return canApply(pca.getPointcut(), targetClass, hasIntroductions);
}
else {
return true;
}
}
public static boolean canApply(Pointcut pc, Class targetClass, boolean hasIntroductions) {
Assert.notNull(pc, "Pointcut must not be null");
if (!pc.getClassFilter().matches(targetClass)) {
return false;
}
MethodMatcher methodMatcher = pc.getMethodMatcher();
if (methodMatcher == MethodMatcher.TRUE) {
return true;
}
IntroductionAwareMethodMatcher introductionAwareMethodMatcher = null;
if (methodMatcher instanceof IntroductionAwareMethodMatcher) {
introductionAwareMethodMatcher = (IntroductionAwareMethodMatcher) methodMatcher;
}
Set> classes = new LinkedHashSet<>(ClassUtils.getAllInterfacesForClassAsSet(targetClass));
classes.add(targetClass);
for (Class clazz : classes) {
//获取当前类的所有方法
Method[] methods = ReflectionUtils.getAllDeclaredMethods(clazz);
for (Method method : methods) {
if ((introductionAwareMethodMatcher != null &&
introductionAwareMethodMatcher.matches(method, targetClass, hasIntroductions)) ||
methodMatcher.matches(method, targetClass)) {
return true;
}
}
}
return false;
}
到这里的时候就进入事务相关的类TransactionAttributeSourcePointcut，看名字就能知道，这是个切点类.那么接下来的逻辑应该可以想象到，无非就是判断是否是个事务方法
到这里的时候就进入事务相关的类TransactionAttributeSourcePointcut，看名字就能知道，这是个切点类.那么接下来的逻辑应该可以想象到，无非就是判断是否是个事务方法
public boolean matches(Method method, @Nullable Class targetClass) {
if (targetClass != null && TransactionalProxy.class.isAssignableFrom(targetClass)) {
return false;
}
TransactionAttributeSource tas = getTransactionAttributeSource();
return (tas == null || tas.getTransactionAttribute(method, targetClass) != null);
}
如果是事务方法则继续往下走
如果是事务方法则继续往下走
public TransactionAttribute getTransactionAttribute(Method method,
@Nullable Class targetClass) {
// 如果当前方法是Object类中的方法，则直接返回
if (method.getDeclaringClass() == Object.class) {
return null;
}
// 获取当前方法缓存使用的key
Object cacheKey = getCacheKey(method, targetClass);
Object cached = this.attributeCache.get(cacheKey);
// 从缓存中获取当前方法解析的事务属性，如果解析过，则将解析结果返回
if (cached != null) {
if (cached == NULL_TRANSACTION_ATTRIBUTE) {
return null;
} else {
return (TransactionAttribute) cached;
}
} else {
// 解析当前方法的事务属性，这里很重要，下面说
TransactionAttribute txAttr = computeTransactionAttribute(method, targetClass);
if (txAttr == null) {
// 如果当前方法上没有事务属性，则缓存一个表示空事务属性的对象
this.attributeCache.put(cacheKey, NULL_TRANSACTION_ATTRIBUTE);
} else {
// 获取方法的签名
String methodIdentification =
ClassUtils.getQualifiedMethodName(method, targetClass);
// 如果生成的事务属性是DefaultTransactionAttribute类型的，则将方法签名设置到其descriptor属性中
if (txAttr instanceof DefaultTransactionAttribute) {
((DefaultTransactionAttribute) txAttr)
.setDescriptor(methodIdentification);
}
if (logger.isDebugEnabled()) {
logger.debug("Adding transactional method '" + methodIdentification
+ "' with attribute: " + txAttr);
}
// 缓存当前方法的解析结果
this.attributeCache.put(cacheKey, txAttr);
}
return txAttr;
}
}
接着看一下方法的事务属性是如何解析的
protected TransactionAttribute computeTransactionAttribute(Method method,
@Nullable Class targetClass) {
// 如果设置了只对public方法进行事务代理，并且当前方法不是public的，则返回null
if (allowPublicMethodsOnly() && !Modifier.isPublic(method.getModifiers())) {
return null;
}
Class userClass = (targetClass != null ?
ClassUtils.getUserClass(targetClass) : null);
// 获取最为准确的方法，即如果传入的method只是一个接口方法，则会去找其实现类的同一方法进行解析
Method specificMethod = ClassUtils.getMostSpecificMethod(method, userClass);
// 如果当前方法是一个泛型方法，则会找Class文件中实际实现的方法
specificMethod = BridgeMethodResolver.findBridgedMethod(specificMethod);
// 解析目标方法，获取其是否存在事务属性，如果存在则直接返回
TransactionAttribute txAttr = findTransactionAttribute(specificMethod);
if (txAttr != null) {
return txAttr;
}
// 解析目标方法所在的类，判断其是否标注有事务属性，如果存在，并且目标方法是用户实现的方法，则直接返回
txAttr = findTransactionAttribute(specificMethod.getDeclaringClass());
if (txAttr != null && ClassUtils.isUserLevelMethod(method)) {
return txAttr;
}
// 如果通过解析到的方法无法找到事务属性，则判断解析得到的方法与传入的目标方法是否为同一个方法，
// 如果不是同一个方法，则尝试对传入的方法及其所在的类进行事务属性解析
if (specificMethod != method) {
// 对传入方法解析事务属性，如果存在，则直接返回
txAttr = findTransactionAttribute(method);
if (txAttr != null) {
return txAttr;
}
// 对传入方法所在类进行事务属性解析，如果存在，则直接返回
txAttr = findTransactionAttribute(method.getDeclaringClass());
if (txAttr != null && ClassUtils.isUserLevelMethod(method)) {
return txAttr;
}
}
return null;
}
这里对事务属性的解析主要分为对目标方法进行解析和对传入方法进行解析，接着看findTransactionAttribute方法
这里对事务属性的解析主要分为对目标方法进行解析和对传入方法进行解析，接着看findTransactionAttribute方法
protected TransactionAttribute findTransactionAttribute(Method method) {
return determineTransactionAttribute(method);
}
protected TransactionAttribute determineTransactionAttribute(AnnotatedElement ae) {
for (TransactionAnnotationParser annotationParser : this.annotationParsers) {
TransactionAttribute attr = annotationParser.parseTransactionAnnotation(ae);
if (attr != null) {
return attr;
}
}
return null;
}
public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) {
AnnotationAttributes attributes = AnnotatedElementUtils.findMergedAnnotationAttributes(
ae, Transactional.class, false, false);
if (attributes != null) {
return parseTransactionAnnotation(attributes);
}
else {
return null;
}
}
public TransactionAttribute parseTransactionAnnotation(AnnotatedElement ae) {
// 判断目标方法上是否存在@Transactional注解，如果不存在，则直接返回
AnnotationAttributes attributes = AnnotatedElementUtils
.findMergedAnnotationAttributes(ae, Transactional.class, false, false);
if (attributes != null) {
// 如果目标方法上存在@Transactional注解，则获取注解值，并且封装为TransactionAttribute返回
return parseTransactionAnnotation(attributes);
} else {
return null;
}
}
protected TransactionAttribute parseTransactionAnnotation(
AnnotationAttributes attributes) {
RuleBasedTransactionAttribute rbta = new RuleBasedTransactionAttribute();
// 获取注解上的propagation值
Propagation propagation = attributes.getEnum("propagation");
rbta.setPropagationBehavior(propagation.value());
// 获取注解上的isolation属性值
Isolation isolation = attributes.getEnum("isolation");
rbta.setIsolationLevel(isolation.value());
// 获取注解上的timeout属性值
rbta.setTimeout(attributes.getNumber("timeout").intValue());
// 获取注解上的readOnly属性值
rbta.setReadOnly(attributes.getBoolean("readOnly"));
// 获取注解上的value属性值
rbta.setQualifier(attributes.getString("value"));
ArrayList rollBackRules = new ArrayList<>();
// 获取注解上的rollbackFor属性列表
Class[] rbf = attributes.getClassArray("rollbackFor");
for (Class rbRule : rbf) {
RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);
rollBackRules.add(rule);
}
// 获取注解上的rollbackForClassName属性列表
String[] rbfc = attributes.getStringArray("rollbackForClassName");
for (String rbRule : rbfc) {
RollbackRuleAttribute rule = new RollbackRuleAttribute(rbRule);
rollBackRules.add(rule);
}
// 获取注解上的noRollbackFor属性列表
Class[] nrbf = attributes.getClassArray("noRollbackFor");
for (Class rbRule : nrbf) {
NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);
rollBackRules.add(rule);
}
// 获取注解上的noRollbackForClassName属性列表
String[] nrbfc = attributes.getStringArray("noRollbackForClassName");
for (String rbRule : nrbfc) {
NoRollbackRuleAttribute rule = new NoRollbackRuleAttribute(rbRule);
rollBackRules.add(rule);
}
rbta.getRollbackRules().addAll(rollBackRules);
return rbta;
}
可以看到这里已经把方法上或者类上的@Transactional注解的属性封装成TransactionAttribute返回了。
在增强BeanFactoryTransactionAttributeSourceAdvisor中包含TransactionInterceptor。spring源码解析之spring事务源码解析(一)中最后,TransactionInterceptor 注入到了BeanFactoryTransactionAttributeSourceAdvisor中，代理的实现就是基于这个拦截器
现在来看一下这个拦截器的代码
public Object invoke(final MethodInvocation invocation) throws Throwable {
Class targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
// 往下看
return invokeWithinTransaction(invocation.getMethod(), targetClass, invocation::proceed);
}
protected Object invokeWithinTransaction(Method method, @Nullable Class targetClass,
final InvocationCallback invocation) throws Throwable {
TransactionAttributeSource tas = getTransactionAttributeSource();
// 获取事务属性
final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
//方法标识，例如usersService.testTransaction
final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);
//声明式事务
if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
// 1.创建TransactionInfo
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
Object retVal = null;
try {
// 2. 调用执行链
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// 3. 异常回滚
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
//4. 清除事务信息
cleanupTransactionInfo(txInfo);
}
//5 提交事务
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
//编程式事务处理
final ThrowableHolder throwableHolder = new ThrowableHolder();
try {
Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr, status -> {
TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
try {
return invocation.proceedWithInvocation();
}
catch (Throwable ex) {
if (txAttr.rollbackOn(ex)) {
if (ex instanceof RuntimeException) {
throw (RuntimeException) ex;
}
else {
throw new ThrowableHolderException(ex);
}
}
else {
throwableHolder.throwable = ex;
return null;
}
}
finally {
cleanupTransactionInfo(txInfo);
}
});
if (throwableHolder.throwable != null) {
throw throwableHolder.throwable;
}
return result;
}
catch (ThrowableHolderException ex) {
throw ex.getCause();
}
catch (TransactionSystemException ex2) {
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
ex2.initApplicationException(throwableHolder.throwable);
}
throw ex2;
}
catch (Throwable ex2) {
if (throwableHolder.throwable != null) {
logger.error("Application exception overridden by commit exception", throwableHolder.throwable);
}
throw ex2;
}
}
}
由于咱们经常使用的就是声明式事务，所以接下来的解析也是基于声明式事务来的
创建事务
protected TransactionInfo createTransactionIfNecessary(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, final String joinpointIdentification) {
//如果事务没有指定名称则使用方法标识
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) {
//1. 创建事务
status = tm.getTransaction(txAttr);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Skipping transactional joinpoint [" + joinpointIdentification +
"] because no transaction manager has been configured");
}
}
}
//2.构建事务信息
return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
}
- 获取事务
public final TransactionStatus getTransaction(@Nullable TransactionDefinition definition) throws TransactionException {
//1. 获取事务
Object transaction = doGetTransaction();
boolean debugEnabled = logger.isDebugEnabled();
if (definition == null) {
definition = new DefaultTransactionDefinition();
}
//2. 判断当前线程是否存在事务
if (isExistingTransaction(transaction)) {
//存在事务则使用嵌套事务处理
return handleExistingTransaction(definition, transaction, debugEnabled);
}
// 事务超时
if (definition.getTimeout() < TransactionDefinition.TIMEOUT_DEFAULT) {
throw new InvalidTimeoutException("Invalid transaction timeout", definition.getTimeout());
}
// 如果当前没有事务，但是事务的传播行为被定义为PROPAGATION_MANDATORY，则抛出异常
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
throw new IllegalTransactionStateException(
"No existing transaction found for transaction marked with propagation 'mandatory'");
}//当事务的传播行为需要新建事务时的处理
else if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRED ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW ||
definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
SuspendedResourcesHolder suspendedResources = suspend(null);
if (debugEnabled) {
logger.debug("Creating new transaction with name [" + definition.getName() + "]: " + definition);
}
try {
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, suspendedResources);
//3. 准备事务
doBegin(transaction, definition);
//4. 记录事务状态
prepareSynchronization(status, definition);
return status;
}
catch (RuntimeException | Error ex) {
resume(null, suspendedResources);
throw ex;
}
}
else {
// 创建空事务
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);
}
}
整个获取事务的过程还是包含多个步骤的，其中doBegin比较值得聊一聊
protected void doBegin(Object transaction, TransactionDefinition definition) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
Connection con = null;
try {
if (!txObject.hasConnectionHolder() ||
txObject.getConnectionHolder().isSynchronizedWithTransaction()) {
Connection newCon = obtainDataSource().getConnection();
if (logger.isDebugEnabled()) {
logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
}
txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
}
txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
//获取当前数据库连接
con = txObject.getConnectionHolder().getConnection();
//获取隔离级别
Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
txObject.setPreviousIsolationLevel(previousIsolationLevel);
// 设置自动提交
if (con.getAutoCommit()) {
txObject.setMustRestoreAutoCommit(true);
if (logger.isDebugEnabled()) {
logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
}
con.setAutoCommit(false);
}
prepareTransactionalConnection(con, definition);
//设置当前线程存在事务的标示
txObject.getConnectionHolder().setTransactionActive(true);
//设置超时时间
int timeout = determineTimeout(definition);
if (timeout != TransactionDefinition.TIMEOUT_DEFAULT) {
txObject.getConnectionHolder().setTimeoutInSeconds(timeout);
}
// 将连接绑定到当前线程
if (txObject.isNewConnectionHolder()) {
TransactionSynchronizationManager.bindResource(obtainDataSource(), txObject.getConnectionHolder());
}
}
catch (Throwable ex) {
if (txObject.isNewConnectionHolder()) {
DataSourceUtils.releaseConnection(con, obtainDataSource());
txObject.setConnectionHolder(null, false);
}
throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
}
}
至于记录事务状态这里先不说，先看一下已存在的事务是如何处理的
private TransactionStatus handleExistingTransaction(
TransactionDefinition definition, Object transaction, boolean debugEnabled)
throws TransactionException {
//判断传播行为是否需要存在事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NEVER) {
throw new IllegalTransactionStateException(
"Existing transaction found for transaction marked with propagation 'never'");
}
//不开启事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NOT_SUPPORTED) {
if (debugEnabled) {
logger.debug("Suspending current transaction");
}
Object suspendedResources = suspend(transaction);
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
return prepareTransactionStatus(
definition, null, false, newSynchronization, debugEnabled, suspendedResources);
}
//总是新建事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_REQUIRES_NEW) {
if (debugEnabled) {
logger.debug("Suspending current transaction, creating new transaction with name [" +
definition.getName() + "]");
}
SuspendedResourcesHolder suspendedResources = suspend(transaction);
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 | Error beginEx) {
resumeAfterBeginException(transaction, suspendedResources, beginEx);
throw beginEx;
}
}
//嵌套事务
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NESTED) {
if (!isNestedTransactionAllowed()) {
throw new NestedTransactionNotSupportedException(
"Transaction manager does not allow nested transactions by default - " +
"specify 'nestedTransactionAllowed' property with value 'true'");
}
if (debugEnabled) {
logger.debug("Creating nested transaction with name [" + definition.getName() + "]");
}
if (useSavepointForNestedTransaction()) {
// Create savepoint within existing Spring-managed transaction,
// through the SavepointManager API implemented by TransactionStatus.
// Usually uses JDBC 3.0 savepoints. Never activates Spring synchronization.
DefaultTransactionStatus status =
prepareTransactionStatus(definition, transaction, false, false, debugEnabled, null);
status.createAndHoldSavepoint();
return status;
}
else {
// Nested transaction through nested begin and commit/rollback calls.
// Usually only for JTA: Spring synchronization might get activated here
// in case of a pre-existing JTA transaction.
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, true, newSynchronization, debugEnabled, null);
doBegin(transaction, definition);
prepareSynchronization(status, definition);
return status;
}
}
// Assumably PROPAGATION_SUPPORTS or PROPAGATION_REQUIRED.
if (debugEnabled) {
logger.debug("Participating in existing transaction");
}
if (isValidateExistingTransaction()) {
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)"));
}
}
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);
}
可以看到记录事务状态是最后一步了
protected void prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition) {
if (status.isNewSynchronization()) {
TransactionSynchronizationManager.setActualTransactionActive(status.hasTransaction());
TransactionSynchronizationManager.setCurrentTransactionIsolationLevel(
definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT ?
definition.getIsolationLevel() : null);
TransactionSynchronizationManager.setCurrentTransactionReadOnly(definition.isReadOnly());
TransactionSynchronizationManager.setCurrentTransactionName(definition.getName());
TransactionSynchronizationManager.initSynchronization();
}
}
构建事务信息
protected TransactionInfo prepareTransactionInfo(@Nullable PlatformTransactionManager tm,
@Nullable TransactionAttribute txAttr, String joinpointIdentification,
@Nullable TransactionStatus status) {
TransactionInfo txInfo = new TransactionInfo(tm, txAttr, joinpointIdentification);
if (txAttr != null)
if (logger.isTraceEnabled()) {
logger.trace("Getting transaction for [" + txInfo.getJoinpointIdentification() + "]");
}
// 记录事务状态
txInfo.newTransactionStatus(status);
}
else {
if (logger.isTraceEnabled())
logger.trace("Don't need to create transaction for [" + joinpointIdentification +
"]: This method isn't transactional.");
}
txInfo.bindToThread();
return txInfo;
}
2.
事务回滚
protected void completeTransactionAfterThrowing(@Nullable TransactionInfo txInfo, Throwable ex) {
//是否存在事务
if (txInfo != null && txInfo.getTransactionStatus() != null) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
"] after exception: " + ex);
}
//是否满足回滚条件，比如是否运行时异常等
if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
try {
//回滚处理
txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by rollback exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException | Error ex2) {
logger.error("Application exception overridden by rollback exception", ex);
throw ex2;
}
}
else {
//不满足回滚条件时同样提交
try {
txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by commit exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException | Error ex2) {
logger.error("Application exception overridden by commit exception", ex);
throw ex2;
}
}
}
}
看看回滚的逻辑
看看回滚的逻辑
public final void rollback(TransactionStatus status) throws TransactionException {
//如果事务完成了就不能回滚
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;
processRollback(defStatus, false);
}
private void processRollback(DefaultTransactionStatus status, boolean unexpected) {
try {
boolean unexpectedRollback = unexpected;
try {
//扩展点
triggerBeforeCompletion(status);
//如果有保存点
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Rolling back transaction to savepoint");
}
//推到保存点
status.rollbackToHeldSavepoint();
}
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction rollback");
}//如果当前事务为独立事务则直接回退
doRollback(status);
}
else {
// Participating in larger transaction
if (status.hasTransaction()) {
if (status.isLocalRollbackOnly() || isGlobalRollbackOnParticipationFailure()) {
if (status.isDebug()) {
logger.debug("Participating transaction failed - marking existing transaction as rollback-only");
}
//不是独立事务标记状态
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");
}
// Unexpected rollback only matters here if we're asked to fail early
if (!isFailEarlyOnGlobalRollbackOnly()) {
unexpectedRollback = false;
}
}
}
catch (RuntimeException | Error ex) {
triggerAfterCompletion(status, TransactionSynchronization.STATUS_UNKNOWN);
throw ex;
}
//扩展点
triggerAfterCompletion(status, TransactionSynchronization.STATUS_ROLLED_BACK);
// Raise UnexpectedRollbackException if we had a global rollback-only marker
if (unexpectedRollback) {
throw new UnexpectedRollbackException(
"Transaction rolled back because it has been marked as rollback-only");
}
}
finally {
//清理资源
cleanupAfterCompletion(status);
}
}
而真的的回滚逻辑则是利用JDBC的回滚逻辑实现的
protected void doRollback(DefaultTransactionStatus status) {
DataSourceTransactionManager.DataSourceTransactionObject txObject = (DataSourceTransactionManager.DataSourceTransactionObject)status.getTransaction();
Connection con = txObject.getConnectionHolder().getConnection();
if (status.isDebug()) {
this.logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
}
try {
con.rollback();
} catch (SQLException var5) {
throw new TransactionSystemException("Could not roll back JDBC transaction", var5);
}
}
- 事务提交
public final void commit(TransactionStatus status) throws TransactionException {
//如果事务已经完成
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;
//如果事务设置了回滚标记则直接回滚
if (defStatus.isLocalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Transactional code has requested rollback");
}
processRollback(defStatus, false);
return;
}
if (!shouldCommitOnGlobalRollbackOnly() && defStatus.isGlobalRollbackOnly()) {
if (defStatus.isDebug()) {
logger.debug("Global transaction is marked as rollback-only but transactional code requested commit");
}
processRollback(defStatus, true);
return;
}
//提交事务
processCommit(defStatus);
}
private void processCommit(DefaultTransactionStatus status) throws TransactionException {
try {
boolean beforeCompletionInvoked = false;
try {
boolean unexpectedRollback = false;
//扩展点的相关调用
prepareForCommit(status);
triggerBeforeCommit(status);
triggerBeforeCompletion(status);
beforeCompletionInvoked = true;
if (status.hasSavepoint()) {
if (status.isDebug()) {
logger.debug("Releasing transaction savepoint");
}
unexpectedRollback = status.isGlobalRollbackOnly();
//清除保存点信息
status.releaseHeldSavepoint();
}
else if (status.isNewTransaction()) {
if (status.isDebug()) {
logger.debug("Initiating transaction commit");
}
unexpectedRollback = status.isGlobalRollbackOnly();
//提交事务，同样这里也是调用的JDBC的方法实现的
doCommit(status);
}
else if (isFailEarlyOnGlobalRollbackOnly()) {
unexpectedRollback = status.isGlobalRollbackOnly();
}
// Throw UnexpectedRollbackException if we have a global rollback-only
// marker but still didn't get a corresponding exception from commit.
if (unexpectedRollback) {
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 | Error ex) {
if (!beforeCompletionInvoked) {
triggerBeforeCompletion(status);
}
doRollbackOnCommitException(status, ex);
throw ex;
}
// 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);
}
}