Implement custom VSCC to validate on basis of ChaincodeProposalPayload - hyperledger-fabric

Question

I am trying to implement custom VSCC (Validation System Chaincode) to add some extra logic on the basis of FunctionName and and the payload data(ChaincodeProposalPayload) . Currently i am able to fetch ChaincodeProposalPayload from ChaincodeActionPayload but the data seems to be encoded.
Following is the code i am using.
// args[0] - function name (not used now)
// args[1] - serialized Envelope
// args[2] - serialized policy
args := stub.GetArgs()
// get the envelope...
env, err := utils.GetEnvelopeFromBlock(args[1])
if err != nil {
logger.Errorf("VSCC error: GetEnvelope failed, err %s", err)
return shim.Error(err.Error())
}
// ...and the payload...
payl, err := utils.GetPayload(env)
if err != nil {
logger.Errorf("VSCC error: GetPayload failed, err %s", err)
return shim.Error(err.Error())
}
// ...and the transaction...
tx, err := utils.GetTransaction(payl.Data)
if err != nil {
logger.Errorf("VSCC error: GetTransaction failed, err %s", err)
return shim.Error(err.Error())
}
// loop through each of the actions within
fmt.Println(len(tx.Actions))
for _, act := range tx.Actions {
cap, err := utils.GetChaincodeActionPayload(act.Payload)
if err != nil {
logger.Errorf("VSCC error: GetChaincodeActionPayload failed, err %s", err)
return shim.Error(err.Error())
}
fmt.Println("payload " + string(cap.ChaincodeProposalPayload))
}
In the console Payload is printed as encoded string like
mycc
invoke
a
b
10
How can i properly decode the payload into json?

Answer 1

Something like this should work:
// ChaincodeProposalPayload
cpp, err := utils.GetChaincodeProposalPayload(cap.ChaincodeProposalPayload)
if err != nil {
logger.Errorf("GetChaincodeProposalPayload failed: %s", err)
return shim.Error(err.Error())
}
// ChaincodeInvocationSpec
cis := &peer.ChaincodeInvocationSpec{}
err = proto.Unmarshal(cpp.Input, cis)
if err != nil {
logger.Errorf("GetChaincodeInvokeSpec failed: %s", err)
return shim.Error(err.Error())
}
spec := &peer.ChaincodeSpec
err = proto.Unmarshal(cis.GetChaincodeSpec(),spec)
if err != nil {
logger.Errorf("Unmarshal ChaincodeSpec failed: %s", err)
return shim.Error(err.Error())
}
ccName := spec.GetChaincodeId().GetName()
ccArgs := spec.GetInput().GetArgs()
fnName := ccArgs[0]
for _, arg := range ccArgs[1:] {
// do what you want with your args
}