org.springframework.transaction.support

## Class AbstractPlatformTransactionManager

- java.lang.Object
- - org.springframework.transaction.support.AbstractPlatformTransactionManager

- All Implemented Interfaces:
    Serializable, PlatformTransactionManager
  Direct Known Subclasses:
    CciLocalTransactionManager, DataSourceTransactionManager, HibernateTransactionManager, HibernateTransactionManager, JdoTransactionManager, JmsTransactionManager, JpaTransactionManager, JtaTransactionManager

      public abstract class AbstractPlatformTransactionManager
      extends Object
      implements PlatformTransactionManager, Serializable

  Abstract base class that implements Spring's standard transaction workflow, serving as basis for concrete platform transaction managers like `JtaTransactionManager`.

  This base class provides the following workflow handling:

  - determines if there is an existing transaction;
  - applies the appropriate propagation behavior;
  - suspends and resumes transactions if necessary;
  - checks the rollback-only flag on commit;
  - applies the appropriate modification on rollback (actual rollback or setting rollback-only);
  - triggers registered synchronization callbacks (if transaction synchronization is active).

  Subclasses have to implement specific template methods for specific states of a transaction, e.g.: begin, suspend, resume, commit, rollback. The most important of them are abstract and must be provided by a concrete implementation; for the rest, defaults are provided, so overriding is optional.

  Transaction synchronization is a generic mechanism for registering callbacks that get invoked at transaction completion time. This is mainly used internally by the data access support classes for JDBC, Hibernate, JPA, etc when running within a JTA transaction: They register resources that are opened within the transaction for closing at transaction completion time, allowing e.g. for reuse of the same Hibernate Session within the transaction. The same mechanism can also be leveraged for custom synchronization needs in an application.

  The state of this class is serializable, to allow for serializing the transaction strategy along with proxies that carry a transaction interceptor. It is up to subclasses if they wish to make their state to be serializable too. They should implement the `java.io.Serializable` marker interface in that case, and potentially a private `readObject()` method (according to Java serialization rules) if they need to restore any transient state.

  Since:
    28.03.2003
  Author:
    Juergen Hoeller
  See Also:
    `setTransactionSynchronization(int)`, `TransactionSynchronizationManager`, `JtaTransactionManager`, Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected static class` | `AbstractPlatformTransactionManager.SuspendedResourcesHolder` Holder for suspended resources.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Log` | `logger`
    `static int` | `SYNCHRONIZATION_ALWAYS` Always activate transaction synchronization, even for "empty" transactions that result from PROPAGATION_SUPPORTS with no existing backend transaction.
    `static int` | `SYNCHRONIZATION_NEVER` Never active transaction synchronization, not even for actual transactions.
    `static int` | `SYNCHRONIZATION_ON_ACTUAL_TRANSACTION` Activate transaction synchronization only for actual transactions, that is, not for empty ones that result from PROPAGATION_SUPPORTS with no existing backend transaction.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AbstractPlatformTransactionManager()`

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `commit(TransactionStatus status)` This implementation of commit handles participating in existing transactions and programmatic rollback requests.
    `protected int` | `determineTimeout(TransactionDefinition definition)` Determine the actual timeout to use for the given definition.
    `protected abstract void` | `doBegin(Object transaction, TransactionDefinition definition)` Begin a new transaction with semantics according to the given transaction definition.
    `protected void` | `doCleanupAfterCompletion(Object transaction)` Cleanup resources after transaction completion.
    `protected abstract void` | `doCommit(DefaultTransactionStatus status)` Perform an actual commit of the given transaction.
    `protected abstract Object` | `doGetTransaction()` Return a transaction object for the current transaction state.
    `protected void` | `doResume(Object transaction, Object suspendedResources)` Resume the resources of the current transaction.
    `protected abstract void` | `doRollback(DefaultTransactionStatus status)` Perform an actual rollback of the given transaction.
    `protected void` | `doSetRollbackOnly(DefaultTransactionStatus status)` Set the given transaction rollback-only.
    `protected Object` | `doSuspend(Object transaction)` Suspend the resources of the current transaction.
    `int` | `getDefaultTimeout()` Return the default timeout that this transaction manager should apply if there is no timeout specified at the transaction level, in seconds.
    `TransactionStatus` | `getTransaction(TransactionDefinition definition)` This implementation handles propagation behavior.
    `int` | `getTransactionSynchronization()` Return if this transaction manager should activate the thread-bound transaction synchronization support.
    `protected void` | `invokeAfterCompletion(List<TransactionSynchronization> synchronizations, int completionStatus)` Actually invoke the `afterCompletion` methods of the given Spring TransactionSynchronization objects.
    `protected boolean` | `isExistingTransaction(Object transaction)` Check if the given transaction object indicates an existing transaction (that is, a transaction which has already started).
    `boolean` | `isFailEarlyOnGlobalRollbackOnly()` Return whether to fail early in case of the transaction being globally marked as rollback-only.
    `boolean` | `isGlobalRollbackOnParticipationFailure()` Return whether to globally mark an existing transaction as rollback-only after a participating transaction failed.
    `boolean` | `isNestedTransactionAllowed()` Return whether nested transactions are allowed.
    `boolean` | `isRollbackOnCommitFailure()` Return whether `doRollback` should be performed on failure of the `doCommit` call.
    `boolean` | `isValidateExistingTransaction()` Return whether existing transactions should be validated before participating in them.
    `protected DefaultTransactionStatus` | `newTransactionStatus(TransactionDefinition definition, Object transaction, boolean newTransaction, boolean newSynchronization, boolean debug, Object suspendedResources)` Create a rae TransactionStatus instance for the given arguments.
    `protected void` | `prepareForCommit(DefaultTransactionStatus status)` Make preparations for commit, to be performed before the `beforeCommit` synchronization callbacks occur.
    `protected void` | `prepareSynchronization(DefaultTransactionStatus status, TransactionDefinition definition)` Initialize transaction synchronization as appropriate.
    `protected DefaultTransactionStatus` | `prepareTransactionStatus(TransactionDefinition definition, Object transaction, boolean newTransaction, boolean newSynchronization, boolean debug, Object suspendedResources)` Create a new TransactionStatus for the given arguments, also initializing transaction synchronization as appropriate.
    `protected void` | `registerAfterCompletionWithExistingTransaction(Object transaction, List<TransactionSynchronization> synchronizations)` Register the given list of transaction synchronizations with the existing transaction.
    `protected void` | `resume(Object transaction, AbstractPlatformTransactionManager.SuspendedResourcesHolder resourcesHolder)` Resume the given transaction.
    `void` | `rollback(TransactionStatus status)` This implementation of rollback handles participating in existing transactions.
    `void` | `setDefaultTimeout(int defaultTimeout)` Specify the default timeout that this transaction manager should apply if there is no timeout specified at the transaction level, in seconds.
    `void` | `setFailEarlyOnGlobalRollbackOnly(boolean failEarlyOnGlobalRollbackOnly)` Set whether to fail early in case of the transaction being globally marked as rollback-only.
    `void` | `setGlobalRollbackOnParticipationFailure(boolean globalRollbackOnParticipationFailure)` Set whether to globally mark an existing transaction as rollback-only after a participating transaction failed.
    `void` | `setNestedTransactionAllowed(boolean nestedTransactionAllowed)` Set whether nested transactions are allowed.
    `void` | `setRollbackOnCommitFailure(boolean rollbackOnCommitFailure)` Set whether `doRollback` should be performed on failure of the `doCommit` call.
    `void` | `setTransactionSynchronization(int transactionSynchronization)` Set when this transaction manager should activate the thread-bound transaction synchronization support.
    `void` | `setTransactionSynchronizationName(String constantName)` Set the transaction synchronization by the name of the corresponding constant in this class, e.g.
    `void` | `setValidateExistingTransaction(boolean validateExistingTransaction)` Set whether existing transactions should be validated before participating in them.
    `protected boolean` | `shouldCommitOnGlobalRollbackOnly()` Return whether to call `doCommit` on a transaction that has been marked as rollback-only in a global fashion.
    `protected AbstractPlatformTransactionManager.SuspendedResourcesHolder` | `suspend(Object transaction)` Suspend the given transaction.
    `protected void` | `triggerBeforeCommit(DefaultTransactionStatus status)` Trigger `beforeCommit` callbacks.
    `protected void` | `triggerBeforeCompletion(DefaultTransactionStatus status)` Trigger `beforeCompletion` callbacks.
    `protected boolean` | `useSavepointForNestedTransaction()` Return whether to use a savepoint for a nested transaction.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### SYNCHRONIZATION_ALWAYS

          public static final int SYNCHRONIZATION_ALWAYS

      Always activate transaction synchronization, even for "empty" transactions that result from PROPAGATION_SUPPORTS with no existing backend transaction.
      See Also:
        `TransactionDefinition.PROPAGATION_SUPPORTS`, `TransactionDefinition.PROPAGATION_NOT_SUPPORTED`, `TransactionDefinition.PROPAGATION_NEVER`, Constant Field Values

    - #### SYNCHRONIZATION_ON_ACTUAL_TRANSACTION

          public static final int SYNCHRONIZATION_ON_ACTUAL_TRANSACTION

      Activate transaction synchronization only for actual transactions, that is, not for empty ones that result from PROPAGATION_SUPPORTS with no existing backend transaction.
      See Also:
        `TransactionDefinition.PROPAGATION_REQUIRED`, `TransactionDefinition.PROPAGATION_MANDATORY`, `TransactionDefinition.PROPAGATION_REQUIRES_NEW`, Constant Field Values

    - #### SYNCHRONIZATION_NEVER

          public static final int SYNCHRONIZATION_NEVER

      Never active transaction synchronization, not even for actual transactions.
      See Also:
        Constant Field Values

    - #### logger

          protected transient Log logger

  - ### Constructor Detail

    - #### AbstractPlatformTransactionManager

          public AbstractPlatformTransactionManager()

  - ### Method Detail

    - #### setTransactionSynchronizationName

          public final void setTransactionSynchronizationName(String constantName)

      Set the transaction synchronization by the name of the corresponding constant in this class, e.g. "SYNCHRONIZATION_ALWAYS".
      Parameters:
        `constantName` - name of the constant
      See Also:
        `SYNCHRONIZATION_ALWAYS`

    - #### setTransactionSynchronization

          public final void setTransactionSynchronization(int transactionSynchronization)

      Set when this transaction manager should activate the thread-bound transaction synchronization support. Default is "always".

      Note that transaction synchronization isn't supported for multiple concurrent transactions by different transaction managers. Only one transaction manager is allowed to activate it at any time.

      See Also:
        `SYNCHRONIZATION_ALWAYS`, `SYNCHRONIZATION_ON_ACTUAL_TRANSACTION`, `SYNCHRONIZATION_NEVER`, `TransactionSynchronizationManager`, `TransactionSynchronization`

    - #### getTransactionSynchronization

          public final int getTransactionSynchronization()

      Return if this transaction manager should activate the thread-bound transaction synchronization support.

    - #### setDefaultTimeout

          public final void setDefaultTimeout(int defaultTimeout)

      Specify the default timeout that this transaction manager should apply if there is no timeout specified at the transaction level, in seconds.

      Default is the underlying transaction infrastructure's default timeout, e.g. typically 30 seconds in case of a JTA provider, indicated by the `TransactionDefinition.TIMEOUT_DEFAULT` value.

      See Also:
        `TransactionDefinition.TIMEOUT_DEFAULT`

    - #### getDefaultTimeout

          public final int getDefaultTimeout()

      Return the default timeout that this transaction manager should apply if there is no timeout specified at the transaction level, in seconds.

      Returns `TransactionDefinition.TIMEOUT_DEFAULT` to indicate the underlying transaction infrastructure's default timeout.

    - #### setNestedTransactionAllowed

          public final void setNestedTransactionAllowed(boolean nestedTransactionAllowed)

      Set whether nested transactions are allowed. Default is "false".

      Typically initialized with an appropriate default by the concrete transaction manager subclass.

    - #### isNestedTransactionAllowed

          public final boolean isNestedTransactionAllowed()

      Return whether nested transactions are allowed.

    - #### setValidateExistingTransaction

          public final void setValidateExistingTransaction(boolean validateExistingTransaction)

      Set whether existing transactions should be validated before participating in them.

      When participating in an existing transaction (e.g. with PROPAGATION_REQUIRES or PROPAGATION_SUPPORTS encountering an existing transaction), this outer transaction's characteristics will apply even to the inner transaction scope. Validation will detect incompatible isolation level and read-only settings on the inner transaction definition and reject participation accordingly through throwing a corresponding exception.

      Default is "false", leniently ignoring inner transaction settings, simply overriding them with the outer transaction's characteristics. Switch this flag to "true" in order to enforce strict validation.

    - #### isValidateExistingTransaction

          public final boolean isValidateExistingTransaction()

      Return whether existing transactions should be validated before participating in them.

    - #### setGlobalRollbackOnParticipationFailure

          public final void setGlobalRollbackOnParticipationFailure(boolean globalRollbackOnParticipationFailure)

      Set whether to globally mark an existing transaction as rollback-only after a participating transaction failed.

      Default is "true": If a participating transaction (e.g. with PROPAGATION_REQUIRES or PROPAGATION_SUPPORTS encountering an existing transaction) fails, the transaction will be globally marked as rollback-only. The only possible outcome of such a transaction is a rollback: The transaction originator cannot make the transaction commit anymore.

      Switch this to "false" to let the transaction originator make the rollback decision. If a participating transaction fails with an exception, the caller can still decide to continue with a different path within the transaction. However, note that this will only work as long as all participating resources are capable of continuing towards a transaction commit even after a data access failure: This is generally not the case for a Hibernate Session, for example; neither is it for a sequence of JDBC insert/update/delete operations.

      Note:This flag only applies to an explicit rollback attempt for a subtransaction, typically caused by an exception thrown by a data access operation (where TransactionInterceptor will trigger a `PlatformTransactionManager.rollback()` call according to a rollback rule). If the flag is off, the caller can handle the exception and decide on a rollback, independent of the rollback rules of the subtransaction. This flag does, however, not apply to explicit `setRollbackOnly` calls on a `TransactionStatus`, which will always cause an eventual global rollback (as it might not throw an exception after the rollback-only call).

      The recommended solution for handling failure of a subtransaction is a "nested transaction", where the global transaction can be rolled back to a savepoint taken at the beginning of the subtransaction. PROPAGATION_NESTED provides exactly those semantics; however, it will only work when nested transaction support is available. This is the case with DataSourceTransactionManager, but not with JtaTransactionManager.

      See Also:
        `setNestedTransactionAllowed(boolean)`, `JtaTransactionManager`

    - #### isGlobalRollbackOnParticipationFailure

          public final boolean isGlobalRollbackOnParticipationFailure()

      Return whether to globally mark an existing transaction as rollback-only after a participating transaction failed.

    - #### setFailEarlyOnGlobalRollbackOnly

          public final void setFailEarlyOnGlobalRollbackOnly(boolean failEarlyOnGlobalRollbackOnly)

      Set whether to fail early in case of the transaction being globally marked as rollback-only.

      Default is "false", only causing an UnexpectedRollbackException at the outermost transaction boundary. Switch this flag on to cause an UnexpectedRollbackException as early as the global rollback-only marker has been first detected, even from within an inner transaction boundary.

      Note that, as of Spring 2.0, the fail-early behavior for global rollback-only markers has been unified: All transaction managers will by default only cause UnexpectedRollbackException at the outermost transaction boundary. This allows, for example, to continue unit tests even after an operation failed and the transaction will never be completed. All transaction managers will only fail earlier if this flag has explicitly been set to "true".

      See Also:
        `UnexpectedRollbackException`

    - #### isFailEarlyOnGlobalRollbackOnly

          public final boolean isFailEarlyOnGlobalRollbackOnly()

      Return whether to fail early in case of the transaction being globally marked as rollback-only.

    - #### setRollbackOnCommitFailure

          public final void setRollbackOnCommitFailure(boolean rollbackOnCommitFailure)

      Set whether `doRollback` should be performed on failure of the `doCommit` call. Typically not necessary and thus to be avoided, as it can potentially override the commit exception with a subsequent rollback exception.

      Default is "false".

      See Also:
        `doCommit(org.springframework.transaction.support.DefaultTransactionStatus)`, `doRollback(org.springframework.transaction.support.DefaultTransactionStatus)`

    - #### isRollbackOnCommitFailure

          public final boolean isRollbackOnCommitFailure()

      Return whether `doRollback` should be performed on failure of the `doCommit` call.

    - #### getTransaction

          public final TransactionStatus getTransaction(TransactionDefinition definition)
                                                 throws TransactionException

      This implementation handles propagation behavior. Delegates to `doGetTransaction`, `isExistingTransaction` and `doBegin`.
      Specified by:
        `getTransaction` in interface `PlatformTransactionManager`
      Parameters:
        `definition` - TransactionDefinition instance (can be `null` for defaults), describing propagation behavior, isolation level, timeout etc.
      Returns:
        transaction status object representing the new or current transaction
      Throws:
        `TransactionException` - in case of lookup, creation, or system errors
        `IllegalTransactionStateException` - if the given transaction definition cannot be executed (for example, if a currently active transaction is in conflict with the specified propagation behavior)
      See Also:
        `doGetTransaction()`, `isExistingTransaction(java.lang.Object)`, `doBegin(java.lang.Object, org.springframework.transaction.TransactionDefinition)`

    - #### prepareTransactionStatus

          protected final DefaultTransactionStatus prepareTransactionStatus(TransactionDefinition definition,
                                                                            Object transaction,
                                                                            boolean newTransaction,
                                                                            boolean newSynchronization,
                                                                            boolean debug,
                                                                            Object suspendedResources)

      Create a new TransactionStatus for the given arguments, also initializing transaction synchronization as appropriate.
      See Also:
        `newTransactionStatus(org.springframework.transaction.TransactionDefinition, java.lang.Object, boolean, boolean, boolean, java.lang.Object)`, `prepareTransactionStatus(org.springframework.transaction.TransactionDefinition, java.lang.Object, boolean, boolean, boolean, java.lang.Object)`

    - #### newTransactionStatus

          protected DefaultTransactionStatus newTransactionStatus(TransactionDefinition definition,
                                                                  Object transaction,
                                                                  boolean newTransaction,
                                                                  boolean newSynchronization,
                                                                  boolean debug,
                                                                  Object suspendedResources)

      Create a rae TransactionStatus instance for the given arguments.

    - #### prepareSynchronization

          protected void prepareSynchronization(DefaultTransactionStatus status,
                                                TransactionDefinition definition)

      Initialize transaction synchronization as appropriate.

    - #### determineTimeout

          protected int determineTimeout(TransactionDefinition definition)

      Determine the actual timeout to use for the given definition. Will fall back to this manager's default timeout if the transaction definition doesn't specify a non-default value.
      Parameters:
        `definition` - the transaction definition
      Returns:
        the actual timeout to use
      See Also:
        `TransactionDefinition.getTimeout()`, `setDefaultTimeout(int)`

    - #### suspend

          protected final AbstractPlatformTransactionManager.SuspendedResourcesHolder suspend(Object transaction)
                                                                                       throws TransactionException

      Suspend the given transaction. Suspends transaction synchronization first, then delegates to the `doSuspend` template method.
      Parameters:
        `transaction` - the current transaction object (or `null` to just suspend active synchronizations, if any)
      Returns:
        an object that holds suspended resources (or `null` if neither transaction nor synchronization active)
      Throws:
        `TransactionException`
      See Also:
        `doSuspend(java.lang.Object)`, `resume(java.lang.Object, org.springframework.transaction.support.AbstractPlatformTransactionManager.SuspendedResourcesHolder)`

    - #### resume

          protected final void resume(Object transaction,
                                      AbstractPlatformTransactionManager.SuspendedResourcesHolder resourcesHolder)
                               throws TransactionException

      Resume the given transaction. Delegates to the `doResume` template method first, then resuming transaction synchronization.
      Parameters:
        `transaction` - the current transaction object
        `resourcesHolder` - the object that holds suspended resources, as returned by `suspend` (or `null` to just resume synchronizations, if any)
      Throws:
        `TransactionException`
      See Also:
        `doResume(java.lang.Object, java.lang.Object)`, `suspend(java.lang.Object)`

    - #### commit

          public final void commit(TransactionStatus status)
                            throws TransactionException

      This implementation of commit handles participating in existing transactions and programmatic rollback requests. Delegates to `isRollbackOnly`, `doCommit` and `rollback`.
      Specified by:
        `commit` in interface `PlatformTransactionManager`
      Parameters:
        `status` - object returned by the `getTransaction` method
      Throws:
        `UnexpectedRollbackException` - in case of an unexpected rollback that the transaction coordinator initiated
        `HeuristicCompletionException` - in case of a transaction failure caused by a heuristic decision on the side of the transaction coordinator
        `TransactionSystemException` - in case of commit or system errors (typically caused by fundamental resource failures)
        `IllegalTransactionStateException` - if the given transaction is already completed (that is, committed or rolled back)
        `TransactionException`
      See Also:
        `TransactionStatus.isRollbackOnly()`, `doCommit(org.springframework.transaction.support.DefaultTransactionStatus)`, `rollback(org.springframework.transaction.TransactionStatus)`

    - #### rollback

          public final void rollback(TransactionStatus status)
                              throws TransactionException

      This implementation of rollback handles participating in existing transactions. Delegates to `doRollback` and `doSetRollbackOnly`.
      Specified by:
        `rollback` in interface `PlatformTransactionManager`
      Parameters:
        `status` - object returned by the `getTransaction` method
      Throws:
        `TransactionSystemException` - in case of rollback or system errors (typically caused by fundamental resource failures)
        `IllegalTransactionStateException` - if the given transaction is already completed (that is, committed or rolled back)
        `TransactionException`
      See Also:
        `doRollback(org.springframework.transaction.support.DefaultTransactionStatus)`, `doSetRollbackOnly(org.springframework.transaction.support.DefaultTransactionStatus)`

    - #### triggerBeforeCommit

          protected final void triggerBeforeCommit(DefaultTransactionStatus status)

      Trigger `beforeCommit` callbacks.
      Parameters:
        `status` - object representing the transaction

    - #### triggerBeforeCompletion

          protected final void triggerBeforeCompletion(DefaultTransactionStatus status)

      Trigger `beforeCompletion` callbacks.
      Parameters:
        `status` - object representing the transaction

    - #### invokeAfterCompletion

          protected final void invokeAfterCompletion(List<TransactionSynchronization> synchronizations,
                                                     int completionStatus)

      Actually invoke the `afterCompletion` methods of the given Spring TransactionSynchronization objects.

      To be called by this abstract manager itself, or by special implementations of the `registerAfterCompletionWithExistingTransaction` callback.

      Parameters:
        `synchronizations` - List of TransactionSynchronization objects
        `completionStatus` - the completion status according to the constants in the TransactionSynchronization interface
      See Also:
        `registerAfterCompletionWithExistingTransaction(Object, java.util.List)`, `TransactionSynchronization.STATUS_COMMITTED`, `TransactionSynchronization.STATUS_ROLLED_BACK`, `TransactionSynchronization.STATUS_UNKNOWN`

    - #### doGetTransaction

          protected abstract Object doGetTransaction()
                                              throws TransactionException

      Return a transaction object for the current transaction state.

      The returned object will usually be specific to the concrete transaction manager implementation, carrying corresponding transaction state in a modifiable fashion. This object will be passed into the other template methods (e.g. doBegin and doCommit), either directly or as part of a DefaultTransactionStatus instance.

      The returned object should contain information about any existing transaction, that is, a transaction that has already started before the current `getTransaction` call on the transaction manager. Consequently, a `doGetTransaction` implementation will usually look for an existing transaction and store corresponding state in the returned transaction object.

      Returns:
        the current transaction object
      Throws:
        `CannotCreateTransactionException` - if transaction support is not available
        `TransactionException` - in case of lookup or system errors
      See Also:
        `doBegin(java.lang.Object, org.springframework.transaction.TransactionDefinition)`, `doCommit(org.springframework.transaction.support.DefaultTransactionStatus)`, `doRollback(org.springframework.transaction.support.DefaultTransactionStatus)`, `DefaultTransactionStatus.getTransaction()`

    - #### isExistingTransaction

          protected boolean isExistingTransaction(Object transaction)
                                           throws TransactionException

      Check if the given transaction object indicates an existing transaction (that is, a transaction which has already started).

      The result will be evaluated according to the specified propagation behavior for the new transaction. An existing transaction might get suspended (in case of PROPAGATION_REQUIRES_NEW), or the new transaction might participate in the existing one (in case of PROPAGATION_REQUIRED).

      The default implementation returns `false`, assuming that participating in existing transactions is generally not supported. Subclasses are of course encouraged to provide such support.

      Parameters:
        `transaction` - transaction object returned by doGetTransaction
      Returns:
        if there is an existing transaction
      Throws:
        `TransactionException` - in case of system errors
      See Also:
        `doGetTransaction()`

    - #### useSavepointForNestedTransaction

          protected boolean useSavepointForNestedTransaction()

      Return whether to use a savepoint for a nested transaction.

      Default is `true`, which causes delegation to DefaultTransactionStatus for creating and holding a savepoint. If the transaction object does not implement the SavepointManager interface, a NestedTransactionNotSupportedException will be thrown. Else, the SavepointManager will be asked to create a new savepoint to demarcate the start of the nested transaction.

      Subclasses can override this to return `false`, causing a further call to `doBegin` - within the context of an already existing transaction. The `doBegin` implementation needs to handle this accordingly in such a scenario. This is appropriate for JTA, for example.

      See Also:
        `AbstractTransactionStatus.createAndHoldSavepoint()`, `AbstractTransactionStatus.rollbackToHeldSavepoint()`, `AbstractTransactionStatus.releaseHeldSavepoint()`, `doBegin(java.lang.Object, org.springframework.transaction.TransactionDefinition)`

    - #### doBegin

          protected abstract void doBegin(Object transaction,
                                          TransactionDefinition definition)
                                   throws TransactionException

      Begin a new transaction with semantics according to the given transaction definition. Does not have to care about applying the propagation behavior, as this has already been handled by this abstract manager.

      This method gets called when the transaction manager has decided to actually start a new transaction. Either there wasn't any transaction before, or the previous transaction has been suspended.

      A special scenario is a nested transaction without savepoint: If `useSavepointForNestedTransaction()` returns "false", this method will be called to start a nested transaction when necessary. In such a context, there will be an active transaction: The implementation of this method has to detect this and start an appropriate nested transaction.

      Parameters:
        `transaction` - transaction object returned by `doGetTransaction`
        `definition` - TransactionDefinition instance, describing propagation behavior, isolation level, read-only flag, timeout, and transaction name
      Throws:
        `TransactionException` - in case of creation or system errors

    - #### doSuspend

          protected Object doSuspend(Object transaction)
                              throws TransactionException

      Suspend the resources of the current transaction. Transaction synchronization will already have been suspended.

      The default implementation throws a TransactionSuspensionNotSupportedException, assuming that transaction suspension is generally not supported.

      Parameters:
        `transaction` - transaction object returned by `doGetTransaction`
      Returns:
        an object that holds suspended resources (will be kept unexamined for passing it into doResume)
      Throws:
        `TransactionSuspensionNotSupportedException` - if suspending is not supported by the transaction manager implementation
        `TransactionException` - in case of system errors
      See Also:
        `doResume(java.lang.Object, java.lang.Object)`

    - #### doResume

          protected void doResume(Object transaction,
                                  Object suspendedResources)
                           throws TransactionException

      Resume the resources of the current transaction. Transaction synchronization will be resumed afterwards.

      The default implementation throws a TransactionSuspensionNotSupportedException, assuming that transaction suspension is generally not supported.

      Parameters:
        `transaction` - transaction object returned by `doGetTransaction`
        `suspendedResources` - the object that holds suspended resources, as returned by doSuspend
      Throws:
        `TransactionSuspensionNotSupportedException` - if resuming is not supported by the transaction manager implementation
        `TransactionException` - in case of system errors
      See Also:
        `doSuspend(java.lang.Object)`

    - #### shouldCommitOnGlobalRollbackOnly

          protected boolean shouldCommitOnGlobalRollbackOnly()

      Return whether to call `doCommit` on a transaction that has been marked as rollback-only in a global fashion.

      Does not apply if an application locally sets the transaction to rollback-only via the TransactionStatus, but only to the transaction itself being marked as rollback-only by the transaction coordinator.

      Default is "false": Local transaction strategies usually don't hold the rollback-only marker in the transaction itself, therefore they can't handle rollback-only transactions as part of transaction commit. Hence, AbstractPlatformTransactionManager will trigger a rollback in that case, throwing an UnexpectedRollbackException afterwards.

      Override this to return "true" if the concrete transaction manager expects a `doCommit` call even for a rollback-only transaction, allowing for special handling there. This will, for example, be the case for JTA, where `UserTransaction.commit` will check the read-only flag itself and throw a corresponding RollbackException, which might include the specific reason (such as a transaction timeout).

      If this method returns "true" but the `doCommit` implementation does not throw an exception, this transaction manager will throw an UnexpectedRollbackException itself. This should not be the typical case; it is mainly checked to cover misbehaving JTA providers that silently roll back even when the rollback has not been requested by the calling code.

      See Also:
        `doCommit(org.springframework.transaction.support.DefaultTransactionStatus)`, `DefaultTransactionStatus.isGlobalRollbackOnly()`, `AbstractTransactionStatus.isLocalRollbackOnly()`, `TransactionStatus.setRollbackOnly()`, `UnexpectedRollbackException`, `UserTransaction.commit()`, `RollbackException`

    - #### prepareForCommit

          protected void prepareForCommit(DefaultTransactionStatus status)

      Make preparations for commit, to be performed before the `beforeCommit` synchronization callbacks occur.

      Note that exceptions will get propagated to the commit caller and cause a rollback of the transaction.

      Parameters:
        `status` - the status representation of the transaction
      Throws:
        `RuntimeException` - in case of errors; will be propagated to the caller (note: do not throw TransactionException subclasses here!)

    - #### doCommit

          protected abstract void doCommit(DefaultTransactionStatus status)
                                    throws TransactionException

      Perform an actual commit of the given transaction.

      An implementation does not need to check the "new transaction" flag or the rollback-only flag; this will already have been handled before. Usually, a straight commit will be performed on the transaction object contained in the passed-in status.

      Parameters:
        `status` - the status representation of the transaction
      Throws:
        `TransactionException` - in case of commit or system errors
      See Also:
        `DefaultTransactionStatus.getTransaction()`

    - #### doRollback

          protected abstract void doRollback(DefaultTransactionStatus status)
                                      throws TransactionException

      Perform an actual rollback of the given transaction.

      An implementation does not need to check the "new transaction" flag; this will already have been handled before. Usually, a straight rollback will be performed on the transaction object contained in the passed-in status.

      Parameters:
        `status` - the status representation of the transaction
      Throws:
        `TransactionException` - in case of system errors
      See Also:
        `DefaultTransactionStatus.getTransaction()`

    - #### doSetRollbackOnly

          protected void doSetRollbackOnly(DefaultTransactionStatus status)
                                    throws TransactionException

      Set the given transaction rollback-only. Only called on rollback if the current transaction participates in an existing one.

      The default implementation throws an IllegalTransactionStateException, assuming that participating in existing transactions is generally not supported. Subclasses are of course encouraged to provide such support.

      Parameters:
        `status` - the status representation of the transaction
      Throws:
        `TransactionException` - in case of system errors

    - #### registerAfterCompletionWithExistingTransaction

          protected void registerAfterCompletionWithExistingTransaction(Object transaction,
                                                                        List<TransactionSynchronization> synchronizations)
                                                                 throws TransactionException

      Register the given list of transaction synchronizations with the existing transaction.

      Invoked when the control of the Spring transaction manager and thus all Spring transaction synchronizations end, without the transaction being completed yet. This is for example the case when participating in an existing JTA or EJB CMT transaction.

      The default implementation simply invokes the `afterCompletion` methods immediately, passing in "STATUS_UNKNOWN". This is the best we can do if there's no chance to determine the actual outcome of the outer transaction.

      Parameters:
        `transaction` - transaction object returned by `doGetTransaction`
        `synchronizations` - List of TransactionSynchronization objects
      Throws:
        `TransactionException` - in case of system errors
      See Also:
        `invokeAfterCompletion(java.util.List, int)`, `TransactionSynchronization.afterCompletion(int)`, `TransactionSynchronization.STATUS_UNKNOWN`

    - #### doCleanupAfterCompletion

          protected void doCleanupAfterCompletion(Object transaction)

      Cleanup resources after transaction completion.

      Called after `doCommit` and `doRollback` execution, on any outcome. The default implementation does nothing.

      Should not throw any exceptions but just issue warnings on errors.

      Parameters:
        `transaction` - transaction object returned by `doGetTransaction`