Spring事务——TransacationInterceptor源码学习

@Nullable
protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass,
 final InvocationCallback invocation) throws Throwable {

 // If the transaction attribute is null, the method is non-transactional.
 TransactionAttributeSource tas = getTransactionAttributeSource();
 final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);　　// 1
 final PlatformTransactionManager tm = determineTransactionManager(txAttr);　　// 2
 final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);　　// 3

 if (txAttr == null || !(tm instanceof CallbackPreferringPlatformTransactionManager)) {
 // Standard transaction demarcation with getTransaction and commit/rollback calls.
 TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification);　　// 4

 Object retVal;
 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.proceedWithInvocation();
 }
 catch (Throwable ex) {
 // target invocation exception
 completeTransactionAfterThrowing(txInfo, ex);
 throw ex;
 }
 finally {
 cleanupTransactionInfo(txInfo);
 }
 commitTransactionAfterReturning(txInfo);
 return retVal;
 }

 else {
 final ThrowableHolder throwableHolder = new ThrowableHolder();

 // It's a CallbackPreferringPlatformTransactionManager: pass a TransactionCallback in.
 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)) {
 // 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.
 throwableHolder.throwable = ex;
 return null;
 }
 }
 finally {
 cleanupTransactionInfo(txInfo);
 }
 });

 // Check result state: It might indicate a Throwable to rethrow.
 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;
 }
 }
}

TransactionAttributeSource tas = getTransactionAttributeSource();
final TransactionAttribute txAttr = (tas != null ? tas.getTransactionAttribute(method, targetClass) : null);
final PlatformTransactionManager tm = determineTransactionManager(txAttr);
final String joinpointIdentification = methodIdentification(method, targetClass, txAttr);

1.TransactionAttribute txAttr由TransactionAttributeSource tas获得，TransationDefinition是TransactionAttribute的基类。txAttr记录了事务的执行方法、事务的传播行为、事务的隔离等级、事务是否只读、事务TimeOut属性和事务名。

　　　　

2.final PlatformTransactionManager。DatasourceTransactionManager实现了PlatformTransactionManager接口，获取的是SpringBean容器中的PlatformTransactionManager(DataSourceTransactionManager)。
　　

前面的步骤返回的全部是null。

3.final String joinpointIdentification，获取@Transactional注解的方法的全限定名。

3.5

4.TransactionInfo txInfo = createTransactionIfNecessary(tm, txAttr, joinpointIdentification); txInfo持有TransactionManager、TransactionAttribute、joinpointIdentification、transactionStatus。