Package net.corda.core.flows

Class SignTransactionFlow

  • All Implemented Interfaces:
    
public abstract class SignTransactionFlow
extends FlowLogic<SignedTransaction>

    The SignTransactionFlow should be called in response to the CollectSignaturesFlow. It automates the signing of a transaction providing the transaction:

    • Should actually be signed by the Party invoking this flow

    • Is valid as per the contracts referenced in the transaction

    • Has been, at least, signed by the counterparty which created it

    • Conforms to custom checking provided in the checkTransaction method of the SignTransactionFlow

    Usage:

    • Subclass SignTransactionFlow - this can be done inside an existing flow (as shown below)

    • Override the checkTransaction method to add some custom verification logic

    • Call the flow via FlowLogic.subFlow

    • The flow returns the transaction signed with the additional signature.

    Example - checking and signing a transaction involving a DummyContract, see CollectSignaturesFlowTests.kt for further examples:

    class Responder(val otherPartySession: FlowSession): FlowLogic<SignedTransaction>() {
     @Suspendable override fun call(): SignedTransaction {
         // [SignTransactionFlow] sub-classed as a singleton object.
         val flow = object : SignTransactionFlow(otherPartySession) {
             @Suspendable override fun checkTransaction(stx: SignedTransaction) = requireThat {
                 val tx = stx.tx
                 val magicNumberState = tx.outputs.single().data as DummyContract.MultiOwnerState
                 "Must be 1337 or greater" using (magicNumberState.magicNumber >= 1337)
             }
         }

         // Invoke the subFlow, in response to the counterparty calling [CollectSignaturesFlow].
         val expectedTxId = subFlow(flow).id

         return subFlow(ReceiveFinalityFlow(otherPartySession, expectedTxId))
     }
 }

    • Constructor Detail

      • SignTransactionFlow

        SignTransactionFlow(FlowSession otherSideSession, ProgressTracker progressTracker)
        Parameters:
        otherSideSession - The session which is providing you a transaction to sign.

    • Method Detail

      • getProgressTracker

         ProgressTracker getProgressTracker()

        Override this to provide a ProgressTracker. If one is provided and stepped, the framework will do something helpful with the progress reports e.g record to the audit service. If this flow is invoked as a subflow of another, then the tracker will be made a child of the current step in the parent. If it's null, this flow doesn't track progress.

        Note that this has to return a tracker before the flow is invoked. You can't change your mind half way through.