Annotations

These pages are a dense lookup of Skipper’s public surface. For usage in context, follow the linked guides.

Annotations are discovered across the full class hierarchy, so they may be declared on abstract base classes and are honored on concrete subclasses.

Annotation	Target	Description
@WorkflowMethod	Workflow method	Declares a workflow entry point. Pass returnType to give the unwrapped type for a Java CompletableFuture return.
@StateField	Workflow field	Marks a field as persisted workflow state, saved and restored when the workflow resumes. No parameters.
@SignalMethod	Workflow method	Injects data into a running workflow (max one serializable parameter). persist = true durably records the signal.
@QueryMethod	Workflow method	Reads workflow state without mutating it. No parameters.
@Execute	Actions method	Declares an action. Optional returnType, retryStrategy, exceptionClassifier, and checkpointMode.
@Compensate	Actions method	Rollback logic for the action named by forExecute. Optional checkpointMode.

A workflow using several of them:

class TransferWorkflow : Workflow() {
  private val ledger = actions<LedgerActions>()

  @StateField var isApproved: Boolean? = null

  @WorkflowMethod
  suspend fun transfer(request: TransferRequest): Boolean {
    if (request.amount > 1000) {
      val ok = waitUntil({ isApproved != null }, Duration.ofDays(1))
      if (!ok || isApproved != true) return false
    }
    ledger.debit(request.from)
    ledger.credit(request.to)
    return true
  }

  @SignalMethod fun approve(approved: Boolean) { isApproved = approved }

  @QueryMethod fun approvalState(): Boolean? = isApproved
}

public class TransferWorkflow extends Workflow {
  private final LedgerActions ledger = actions(LedgerActions.class);

  @StateField Boolean isApproved;

  @WorkflowMethod(returnType = Boolean.class)
  public CompletableFuture<Boolean> transfer(TransferRequest request) {
    if (request.getAmount() > 1000) {
      boolean ok = waitUntil(() -> isApproved != null, Duration.ofDays(1));
      if (!ok || !Boolean.TRUE.equals(isApproved)) return CompletableFuture.completedFuture(false);
    }
    ledger.debit(request.getFrom());
    ledger.credit(request.getTo());
    return CompletableFuture.completedFuture(true);
  }

  @SignalMethod
  public void approve(boolean approved) { isApproved = approved; }

  @QueryMethod
  public Boolean approvalState() { return isApproved; }
}