Requirements for Annotated Methods

When using the annotation-based DSL, your handler and validator methods must follow strict signature requirements to ensure correct processing. Here are the requirements for each type:

@Handle Methods

• Must have exactly 4 parameters in this order:
  1. The state enum type (e.g., PaymentState)
  2. The request type (e.g., PaymentRequest)
  3. The command type (as defined in your @Action(command = ...))
  4. A StateMutator (from the framework)
• Example:

  @Handle
  public void handle(PaymentState state, PaymentRequest req, SubmitPaymentCommand cmd, StateMutator mutator) {
      // ...
  }

• Common error: Wrong parameter count or wrong types/order will result in an error: @Handle method must have exactly 4 parameters (state, request, command, mutator)

In-State Validator Methods

• Must have exactly 3 parameters in this order:
  1. The state enum type
  2. The request type
  3. The validation context (usually ValidationContext)
• Example:

  public void validate(PaymentState state, PaymentRequest req, ValidationContext ctx) {
      // ...
  }

• Common error: Wrong parameter count or wrong types/order will result in an error: InStateValidator 'validate' method must have exactly 3 parameters (state, request, ctx)

Transition Validator Methods

• Must have exactly 4 parameters in this order:
  1. From-state (state enum type)
  2. To-state (state enum type)
  3. The request type
  4. The validation context (usually ValidationContext)
• Example:

  public void validate(PaymentState from, PaymentState to, PaymentRequest req, ValidationContext ctx) {
      // ...
  }

• Common error: Wrong parameter count or wrong types/order will result in an error: TransitionValidator 'validate' method must have exactly 4 parameters (from, to, request, ctx)

Troubleshooting

• If you see errors about parameter counts or types, double-check your method signatures against the above requirements.
• All types must match exactly (including generics if used).
• For more advanced usage or to bypass annotation restrictions, use the builder DSL in the core module.