升级一些Corda3源代码以在v4上运行

Question

首先，我3个月前才开始学习corda，所以我还有一些学习要做。

我继承了一些在CordaV3.3下运行良好的代码，但客户希望它能在v4上运行。我正试着按照主网站上的说明去做。我有一个启动流，它调用一个子流，而子流又调用一个转发器流。

启动流：

@InitiatingFlow(version = 2)
@StartableByRPC
class TransferFlow(private val issuerName: String = "",
                   private val seller: String = "",
                   private val amount: BigDecimal = BigDecimal("0"),
                   private val buyer: String = "",
                   private val custodianNameOfBuyer: String = "",
                   private val notaryName: String = "") : FlowLogic<SignedTransaction>() {
    @Suspendable
    override fun call(): SignedTransaction {

        subFlow(UpdateStatusOfTransferFlow(
                sessions,
                tokenTransferAgreement.linearId,
                "Removed Tokens From Seller"))
  }
}

class UpdateStatusOfTransferFlow(
        private val sessions: Set<FlowSession>,
        private val tokenTransferAgreementID: UniqueIdentifier,
        private val newStatus: String) : FlowLogic<SignedTransaction>() {
    @Suspendable
    override fun call(): SignedTransaction {
        sessions.size
        val idQueryCriteria = QueryCriteria.LinearStateQueryCriteria(linearId = listOf(tokenTransferAgreementID))
        val states = serviceHub.vaultService.queryBy<TokenTransferAgreement>(idQueryCriteria).states

        if (states.size != 1) throw FlowException("Can not find a unique state for $tokenTransferAgreementID")

        val inputStateAndRef = states.single()
        val inputState = inputStateAndRef.state.data

        val notary = inputStateAndRef.state.notary

        val outputState = inputState.withNewStatus(newStatus)

        val cmd = Command(TokenContract.Commands.UpdateStatusOfTransfer(),
                inputState.participants.map { it.owningKey })


        val txBuilder = TransactionBuilder(notary = notary)
        txBuilder.addCommand(cmd)
        txBuilder.addInputState(inputStateAndRef)
        txBuilder.addOutputState(outputState, TokenContract.ID)

        txBuilder.verify(serviceHub)
        val ptx = serviceHub.signInitialTransaction(txBuilder)
        val sessions2 = (inputState.participants.toSet() - ourIdentity).map { initiateFlow(it) }

       return subFlow(CollectSignaturesFlow(ptx, sessions2))

    }

}

And the responder:

@InitiatedBy(TransferFlowResponder::class)
class UpdateStatusOfTransferFlowResponder(private val session: FlowSession) : FlowLogic<Unit>() {
    @Suspendable
    override fun call() {
        val tokenTransferAgreements = mutableListOf<TokenTransferAgreement>()
        var isBuyer = true
        var notary = CordaUtility.getNotary(serviceHub) ?: throw FlowException("An notary is expected!")

        val signedTransactionFlow = subFlow(object : SignTransactionFlow(session) {
            override fun checkTransaction(stx: SignedTransaction) = requireThat {
                "There must be one output!" using (stx.tx.outputStates.size == 1)

                val tokenTransferAgreement = stx.tx.outputStates.first() as TokenTransferAgreement
                tokenTransferAgreements.add(tokenTransferAgreement)

                notary = stx.notary ?: throw FlowException("An notary is expected!")

                if (ourIdentity == tokenTransferAgreement.issuer) {
                   //checks go here
                 }

        })
    }

}

我相信我应该在某个时刻添加一个对ReceiveFinality flow的调用，但是它只需要一个会话作为参数，而不是像我在这里使用的列表。我是否应该进行多个调用，每个会话一个？我也不确定调用应该放在转发器还是UpdateStatusOfTransferFlow类中。

如果能帮上忙，我们将不胜感激。

Answer 1

FinalityFlow主要负责确保交易经过公证、相应地分发并持久保存到本地保管库。

在以前的Corda版本中，默认情况下，所有节点都会接受传入的终结性请求。

从V4开始，您需要编写一个ReceiveFinalityFlow，以便在finality之前编写自己的处理逻辑。

finality当前在Corda中运行的方式是发起节点，作为finality期间的中间步骤，将经公证的交易分发给所有其他参与者。它发送到的每个参与节点将仅期望从该节点接收会话。

因此，在您可能向发起FinalityFlow提交多个会话以包括所有参与者的情况下，响应节点将仅从发起者接收一个会话。

将来，我们可能会考虑让公证员将经过公证的交易分发给所有参与者，但即使这样，ReceiveFinalityFlow仍然只会期待一个会话，这次是公证员。