This release introduces significant updates to the Flow payment sessions API, focusing on unifying and simplifying request/response types, improving type safety, and adding extensible configuration entities for payment methods. The changes modernize the Flow client interface, update serialization logic, and introduce new configuration/data classes for payment sessions.

Flow API Modernization and Type Unification:

• The FlowClient and FlowClientImpl interfaces have been refactored to use unified request and response types (PaymentSessionCreateRequest, PaymentSessionSubmitRequest, PaymentSessionCompleteRequest, and PaymentSubmissionResponse) instead of split request/response classes for each operation. This simplifies the API and improves consistency. [1] [2] [3]

• The method signatures and validation logic in FlowClientImpl have been updated to match the new types and naming conventions, ensuring clearer parameter validation and more maintainable code.

Serialization Enhancements:

• The GsonSerializer now registers a type adapter factory for the new PaymentSubmissionResponse polymorphic hierarchy, enabling proper deserialization based on payment session status (approved, declined, action required). [1] [2]

• A new constant STATUS is added to CheckoutUtils to support status-based polymorphic deserialization.

New Payment Session Entities and Configuration:

• Introduces new configuration/data classes for the Flow payment sessions API:
  • ApplePayConfiguration, GooglePayConfiguration, and CardConfiguration provide extensible configuration options for specific payment methods. [1] [2] [3]
  • Customer and its nested CustomerSummary class encapsulate comprehensive customer information and transaction history for risk assessment.
  • CustomerRetry defines retry logic for asynchronous payment attempts.
  • PaymentAction models instructions for further customer action when required (e.g., redirects, additional data).