17.4. List of Mediation States

Domain handlers: In this state all the handlers defined in switchyard.xml are executed. This is an early phase of mediation where you can either implement own logic or choose the service provider logic to use.
Addressing: If this is not specified by the domain handlers then the addressing handler will determine what to do by using the consumer contract.
Transaction: If the service is required to run a transaction this handler starts it.
Security: This state verifies constraints related to authentication and authorization.
General policy: This executes checks other than those for security and transactions.
Validation: This executes custom validators.
Transformation: This prepares the payload by calling a provider.
Validation (2): This validates the transformed payload.
Provider call: This calls the provisional service.
Transaction (2): This commits or, if necessary, rolls back the transaction.

If the service consumer is synchronous and the exchange pattern is set to in-out, then some of these handlers may be called once again:

Domain handlers: These are called when a response is generated by a provider service.
Validation: This verifies the output generated by the provider.
Transformation: This converts the payload to the structure required by the consumer.
Validation: This checks the output after the transformation has occurred.
Consumer callback: This returns the exchange to the service consumer.