执行代理对象的方法时，会遍历其前面类。最终会执行到事务的切面TransactionInterceptor.invoke(final MethodInvocation invocation)
public Object invoke(final MethodInvocation invocation) throws Throwable {
// Work out the target class: may be <code>null</code>.
// 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);
// If the transaction attribute is null, the method is non-transactional.
final TransactionAttribute txAttr =
getTransactionAttributeSource().getTransactionAttribute(invocation.getMethod(), targetClass);
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
final String joinpointIdentification = methodIdentification(invocation.getMethod(), 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 {
// This is an around advice: Invoke the next interceptor in the chain.
// This will normally result in a target object being invoked.
retVal = invocation.proceed();
}
catch (Throwable ex) {
// target invocation exception
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
finally {
cleanupTransactionInfo(txInfo);
}
commitTransactionAfterReturning(txInfo);
return retVal;
}
else {
// It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
try {
Object result = ((CallbackPreferringPlatformTransactionManager) tm).execute(txAttr,
new TransactionCallback<Object>() {
public Object doInTransaction(TransactionStatus status) {
TransactionInfo txInfo = prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
try {
return invocation.proceed();
}
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();
}
}
}
1.获取与执行方法匹配的attribute节点：<tx:method name="*" propagation="REQUIRED"/>
final TransactionAttribute txAttr = getTransactionAttributeSource().getTransactionAttribute(invocation.getMethod(), targetClass);
getTransactionAttributeSource()在其父类TransactionAspectSupport中实现:
public TransactionAttributeSource getTransactionAttributeSource() {
return this.transactionAttributeSource;
}其来源在解析配置文件的时候TxAdviceBeanDefinitionParser.doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder)中有
builder.addPropertyValue("transactionAttributeSource", attributeSourceDefinition);
那么返回的是NameMatchTransactionAttributeSource实例。
NameMatchTransactionAttributeSource.getTransactionAttribute(invocation.getMethod(), targetClass)：
public TransactionAttribute getTransactionAttribute(Method method, Class<?> targetClass) {
// look for direct name match
String methodName = method.getName();
TransactionAttribute attr = this.nameMap.get(methodName);
if (attr == null) {
// Look for most specific name match.
String bestNameMatch = null;
for (String mappedName : this.nameMap.keySet()) {
if (isMatch(methodName, mappedName) &&
(bestNameMatch == null || bestNameMatch.length() <= mappedName.length())) {
attr = this.nameMap.get(mappedName);
bestNameMatch = mappedName;
}
}
}
return attr;
}
protected boolean isMatch(String methodName, String mappedName) {
return PatternMatchUtils.simpleMatch(mappedName, methodName);
}
PatternMatchUtils
public static boolean simpleMatch(String pattern, String str) {
if (pattern == null || str == null) {
return false;
}
int firstIndex = pattern.indexOf('*');
if (firstIndex == -1) {
return pattern.equals(str);
}
if (firstIndex == 0) {
if (pattern.length() == 1) {
return true;
}
int nextIndex = pattern.indexOf('*', firstIndex + 1);
if (nextIndex == -1) {
return str.endsWith(pattern.substring(1));
}
String part = pattern.substring(1, nextIndex);
int partIndex = str.indexOf(part);
while (partIndex != -1) {
if (simpleMatch(pattern.substring(nextIndex), str.substring(partIndex + part.length()))) {
return true;
}
partIndex = str.indexOf(part, partIndex + 1);
}
return false;
}
return (str.length() >= firstIndex &&
pattern.substring(0, firstIndex).equals(str.substring(0, firstIndex)) &&
simpleMatch(pattern.substring(firstIndex), str.substring(firstIndex)));
}
匹配当前执行的方法名称是否符合<tx:method>配置的方法名。
返回的是RuleBasedTransactionAttribute对象。
2.获取事务管理对象，根据配置应该是DataSourceTransactionManager对象。
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
determineTransactionManager(TransactionAttribute txAttr)在其父类TransactionAspectSupport中实现
protected PlatformTransactionManager determineTransactionManager(TransactionAttribute txAttr) {
if (this.transactionManager != null || this.beanFactory == null || txAttr == null) {
return this.transactionManager;
}
String qualifier = txAttr.getQualifier();
if (StringUtils.hasLength(qualifier)) {
return BeanFactoryAnnotationUtils.qualifiedBeanOfType(this.beanFactory, PlatformTransactionManager.class, qualifier);
}
else if (this.transactionManagerBeanName != null) {
return this.beanFactory.getBean(this.transactionManagerBeanName, PlatformTransactionManager.class);
}
else if (this.beanFactory instanceof ListableBeanFactory) {
return BeanFactoryUtils.beanOfTypeIncludingAncestors(((ListableBeanFactory) this.beanFactory), PlatformTransactionManager.class);
}
else {
throw new IllegalStateException(
"Cannot retrieve PlatformTransactionManager beans from non-listable BeanFactory: " + this.beanFactory);
}
}
return this.transactionManager;
这个也是在TxAdviceBeanDefinitionParser.doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder)中设置的。
tm是DataSourceTransactionManager的对象。
3.切入点，当前执行方法。
final String joinpointIdentification = methodIdentification(invocation.getMethod(), targetClass);
在其父类TransactionAspectSupport中实现
protected String methodIdentification(Method method, Class targetClass) {
String simpleMethodId = methodIdentification(method);
if (simpleMethodId != null) {
return simpleMethodId;
}
return (targetClass != null ? targetClass : method.getDeclaringClass()).getName() + "." + method.getName();
}
protected String methodIdentification(Method method) {
return null;
}4.TransactionInfo是TransactionAspectSupport的内部类，是一个简单的pojo。类中含有事务的相关对象，并且会与线程绑定。
TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);
protected TransactionInfo createTransactionIfNecessary(4.1、返回TransactionStatus对象。status = tm.getTransaction(txAttr);
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) {
status = tm.getTransaction(txAttr);
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Skipping transactional joinpoint [" + joinpointIdentification +
"] because no transaction manager has been configured");
}
}
}
return prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
}
DataSourceTransactionManager继承了AbstractPlatformTransactionManager
public final TransactionStatus getTransaction(TransactionDefinition definition) throws TransactionException {
Object transaction = doGetTransaction();
// Cache debug flag to avoid repeated checks.
boolean debugEnabled = logger.isDebugEnabled();
if (definition == null) {
// Use defaults if no transaction definition given.
definition = new DefaultTransactionDefinition();
}
if (isExistingTransaction(transaction)) {
// Existing transaction found -> check propagation behavior to find out how to behave.
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());
}
// No existing transaction found -> check propagation behavior to find out how to proceed.
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_MANDATORY) {
throw new IllegalTransactionStateException(
"No existing transaction found for transaction marked with propagation 'mandatory'");
}
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);
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 {
// Create "empty" transaction: no actual transaction, but potentially synchronization.
boolean newSynchronization = (getTransactionSynchronization() == SYNCHRONIZATION_ALWAYS);
return prepareTransactionStatus(definition, null, true, newSynchronization, debugEnabled, null);
}
}
4.1.1、isExistingTransaction(transaction)判断线程中是否有事务
protected boolean isExistingTransaction(Object transaction) {
DataSourceTransactionObject txObject = (DataSourceTransactionObject) transaction;
return (txObject.getConnectionHolder() != null && txObject.getConnectionHolder().isTransactionActive());
}4.1.2、handleExistingTransaction(definition, transaction, debugEnabled);
判断当前的事务的传播属性，进行相关的操作：required_new、nested等
private TransactionStatus handleExistingTransaction(4.1.3如果当前线程中没有事务，则要创建事务：
TransactionDefinition definition, Object transaction, boolean debugEnabled)
throws TransactionException {
if (definition.getPropagationBehavior() == TransactionDefinition.PROPAGATION_NEVER) {
throw new IllegalTransactionStateException(
"Existing transaction found for transaction marked with propagation 'never'");
}
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);
}
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 beginEx) {
resumeAfterBeginException(transaction, suspendedResources, beginEx);
throw beginEx;
}
catch (Error beginErr) {
resumeAfterBeginException(transaction, suspendedResources, beginErr);
throw beginErr;
}
}
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");
}
}
}
//request的事务，
boolean newSynchronization = (getTransactionSynchronization() != SYNCHRONIZATION_NEVER);
return prepareTransactionStatus(definition, transaction, false, newSynchronization, debugEnabled, null);
}
protected final DefaultTransactionStatus prepareTransactionStatus(
TransactionDefinition definition, Object transaction, boolean newTransaction,
boolean newSynchronization, boolean debug, Object suspendedResources) {
DefaultTransactionStatus status = newTransactionStatus(
definition, transaction, newTransaction, newSynchronization, debug, suspendedResources);
prepareSynchronization(status, definition);
return status;
}
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();
}
}
doBegin(transaction, definition);在DataSourceTransaction中实现。
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();
if (logger.isDebugEnabled()) {
logger.debug("Acquired Connection [" + newCon + "] for JDBC transaction");
}
txObject.setConnectionHolder(new ConnectionHolder(newCon), true);
}
txObject.getConnectionHolder().setSynchronizedWithTransaction(true);
con = txObject.getConnectionHolder().getConnection();
Integer previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
txObject.setPreviousIsolationLevel(previousIsolationLevel);
// Switch to manual commit if necessary. This is very expensive in some JDBC drivers,
// so we don't want to do it unnecessarily (for example if we've explicitly
// configured the connection pool to set it already).
if (con.getAutoCommit()) {
txObject.setMustRestoreAutoCommit(true);
if (logger.isDebugEnabled()) {
logger.debug("Switching JDBC Connection [" + con + "] to manual commit");
}
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 (Exception ex) {
DataSourceUtils.releaseConnection(con, this.dataSource);
throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
}
}
4.2、将事务信息绑定到线程中
prepareTransactionInfo(tm, txAttr, joinpointIdentification, status);
protected TransactionInfo prepareTransactionInfo(PlatformTransactionManager tm,5.completeTransactionAfterThrowing(txInfo, ex);抛出异常时，事务的处理
TransactionAttribute txAttr, String joinpointIdentification, TransactionStatus status) {
TransactionInfo txInfo = new TransactionInfo(tm, txAttr, joinpointIdentification);
if (txAttr != null) {
// We need a transaction for this method
if (logger.isTraceEnabled()) {
logger.trace("Getting transaction for [" + txInfo.getJoinpointIdentification() + "]");
}
// The transaction manager will flag an error if an incompatible tx already exists
txInfo.newTransactionStatus(status);
}
else {
// The TransactionInfo.hasTransaction() method will return
// false. We created it only to preserve the integrity of
// the ThreadLocal stack maintained in this class.
if (logger.isTraceEnabled())
logger.trace("Don't need to create transaction for [" + joinpointIdentification +
"]: This method isn't transactional.");
}
// We always bind the TransactionInfo to the thread, even if we didn't create
// a new transaction here. This guarantees that the TransactionInfo stack
// will be managed correctly even if no transaction was created by this aspect.
txInfo.bindToThread();
return txInfo;
}
protected void completeTransactionAfterThrowing(TransactionInfo txInfo, Throwable ex) {
if (txInfo != null && txInfo.hasTransaction()) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() +
"] after exception: " + ex);
}
if (txInfo.transactionAttribute.rollbackOn(ex)) {
try {
txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
}
catch (TransactionSystemException ex2) {
logger.error("Application exception overridden by rollback exception", ex);
ex2.initApplicationException(ex);
throw ex2;
}
catch (RuntimeException ex2) {
logger.error("Application exception overridden by rollback exception", ex);
throw ex2;
}
catch (Error err) {
logger.error("Application exception overridden by rollback error", ex);
throw err;
}
}
else {
// We don't roll back on this exception.
// Will still roll back if TransactionStatus.isRollbackOnly() is true.
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 ex2) {
logger.error("Application exception overridden by commit exception", ex);
throw ex2;
}
catch (Error err) {
logger.error("Application exception overridden by commit error", ex);
throw err;
}
}
}
}
6.cleanupTransactionInfo(txInfo);清理事务信息
protected void cleanupTransactionInfo(TransactionInfo txInfo) {
if (txInfo != null) {
txInfo.restoreThreadLocalStatus();
}
}
7.正常操作完成后，提交事务。commitTransactionAfterReturning(txInfo);
protected void commitTransactionAfterReturning(TransactionInfo txInfo) {
if (txInfo != null && txInfo.hasTransaction()) {
if (logger.isTraceEnabled()) {
logger.trace("Completing transaction for [" + txInfo.getJoinpointIdentification() + "]");
}
txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
}
}事务的处理是AOP一个例子。