How to add FlowException inside Flow in Corda? - corda

Question

I am trying to add FlowException inside Corda Flow.
I have added the following part in my code. This is always true. I just want to display the message "Trade id already available"
val a : Int = 10
val b : Int = 10
if (a == b){
throw FlowException("Trade id already available")
}
When i run the code, since Flows end pre-maturely due to exceptions, it should dispays the Flow exception error. But only thing it is doing is ending the flow not displaying the message
My complete code is:
object ExampleFlow {
#InitiatingFlow
#StartableByRPC
class Initiator(val iouValue: Int,
val otherParty: Party) : FlowLogic<SignedTransaction>() {
#Suspendable
override fun call(): SignedTransaction {
// Obtain a reference to the notary we want to use.
val notary = serviceHub.networkMapCache.notaryIdentities[0]
val a : Int = 10
val b : Int = 10
if (a == b){
throw FlowException("Trade id already available")
}
val iouState = IOUState(iouValue, serviceHub.myInfo.legalIdentities.first(), otherParty)
val txCommand = Command(IOUContract.Commands.Create(), iouState.participants.map { it.owningKey })
val txBuilder = TransactionBuilder(notary)
.addOutputState(iouState, IOUContract.ID)
.addCommand(txCommand)
txBuilder.verify(serviceHub)
val partSignedTx = serviceHub.signInitialTransaction(txBuilder)
val otherPartySession = initiateFlow(otherParty)
val fullySignedTx = subFlow(CollectSignaturesFlow(partSignedTx, setOf(otherPartySession), GATHERING_SIGS.childProgressTracker()))
return subFlow(FinalityFlow(fullySignedTx, setOf(otherPartySession), FINALISING_TRANSACTION.childProgressTracker()))
}
}
#InitiatedBy(Initiator::class)
class Acceptor(val otherPartySession: FlowSession) : FlowLogic<SignedTransaction>() {
#Suspendable
override fun call(): SignedTransaction {
val signTransactionFlow = object : SignTransactionFlow(otherPartySession) {
override fun checkTransaction(stx: SignedTransaction) = requireThat {
val output = stx.tx.outputs.single().data
"This must be an IOU transaction." using (output is IOUState)
val iou = output as IOUState
"I won't accept IOUs with a value over 100." using (iou.value <= 100)
}
}
val txId = subFlow(signTransactionFlow).id
return subFlow(ReceiveFinalityFlow(otherPartySession, expectedTxId = txId))
}
}
}

Answer 1

It worked for me, I used the same code as yours:
#Suspendable
override fun call(): SignedTransaction {
// Obtain a reference to the notary we want to use.
val notary = serviceHub.networkMapCache.notaryIdentities[0]
val a : Int = 10
val b : Int = 10
if (a == b){
throw FlowException("Trade id already available")
}
// Stage 1.
progressTracker.currentStep = GENERATING_TRANSACTION
// Generate an unsigned transaction.
val iouState = IOUState(iouValue, serviceHub.myInfo.legalIdentities.first(), otherParty)
val txCommand = Command(IOUContract.Commands.Create(), iouState.participants.map { it.owningKey })
val txBuilder = TransactionBuilder(notary)
.addOutputState(iouState, IOUContract.ID)
.addCommand(txCommand)
// Stage 2.
progressTracker.currentStep = VERIFYING_TRANSACTION
// Verify that the transaction is valid.
txBuilder.verify(serviceHub)
// Stage 3.
progressTracker.currentStep = SIGNING_TRANSACTION
// Sign the transaction.
val partSignedTx = serviceHub.signInitialTransaction(txBuilder)
// Stage 4.
progressTracker.currentStep = GATHERING_SIGS
// Send the state to the counterparty, and receive it back with their signature.
val otherPartySession = initiateFlow(otherParty)
val fullySignedTx = subFlow(CollectSignaturesFlow(partSignedTx, setOf(otherPartySession), GATHERING_SIGS.childProgressTracker()))
// Stage 5.
progressTracker.currentStep = FINALISING_TRANSACTION
// Notarise and record the transaction in both parties' vaults.
return subFlow(FinalityFlow(fullySignedTx, setOf(otherPartySession), FINALISING_TRANSACTION.childProgressTracker()))
}
Here's the node shell: