from django.db import transaction

class TransactionMiddleware(object):

    """

    Transaction middleware. If this is enabled, each view function will be run

    with commit_on_response activated - that way a save() doesn't do a direct

    commit, the commit is done when a successful response is created. If an

    exception happens, the database is rolled back.

    """

    def process_request(self, request):

        """Enters transaction management"""

        transaction.enter_transaction_management()

        transaction.managed(True)

    def process_exception(self, request, exception):

        """Rolls back the database and leaves transaction management"""

        if transaction.is_dirty():

            transaction.rollback()

        transaction.leave_transaction_management()

    def process_response(self, request, response):

        """Commits and leaves transaction management."""

        if transaction.is_managed():

            if transaction.is_dirty():

                transaction.commit()

            transaction.leave_transaction_management()

        return response