bezant-chaincode-samples-go

Hypledger fabric chaincode samples go

• Simple: Basic example that uses chaincode to query and execute transaction

Upload partner admin site

1. Download file and upload

• simple-go.zip: You have to download zip file and upload

2. Compress source file and upload

• Only source, vendor files need to be compressed

  zip -r chaincode.zip vendor simpleChaincode.go chaincodeUtil.go
  

Environment

• Go
• Hyperledger Fabric

Download code

$ git clone https://github.com/bezant-developers/bezant-chaincode-samples-go.git

Basic code

package main

import (
	"fmt"

	"github.com/hyperledger/fabric/core/chaincode/shim"
	pb "github.com/hyperledger/fabric/protos/peer"
)

type SimpleChaincode struct {
}

func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
	return shim.Success(nil)
}

func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response {
	return shim.Success(nil)
}

func main() {
	err := shim.Start(new(SimpleChaincode))
	if err != nil {
		fmt.Printf("Error starting Simple chaincode: %s", err)
	}
}

Function

Init is called during chaincode instantiation to initialize and chaincode upgrade also calls this function.

func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
	fmt.Println("========= Init =========")
	return shim.Success(nil)
}

The Invoke method is called in response to receiving an invoke transaction to process transaction proposals.

func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response {
	fmt.Println("========= Invoke =========")
	function, args := stub.GetFunctionAndParameters()

	if function == "put" {
		return t.put(stub, args)
	} else if function == "get" {
		return t.get(stub, args)
	}

	return shim.Error("No function name : " + function + " found")
}

Save the keys and values to the ledger.

func (t *SimpleChaincode) put(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var err error
	var keyString, valString string

	if len(args) != 2 {
		return shim.Error("Incorrect number of arguments. Expecting 2")
	}

	keyString = args[0]
	valString = args[1]

	err = stub.PutState(keyString, []byte(valString))
	if err != nil {
		return shim.Error(err.Error())
	}

	return shim.Success(nil)
}

Get returns the value of the specified asset key

func (t *SimpleChaincode) get(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var keyString string
	var err error

	if len(args) != 1 {
		return shim.Error("Incorrect number of arguments. Expecting 1")
	}

	keyString = args[0]

	// Get the state from the ledger
	resultValueBytes, err := stub.GetState(keyString)
	if err != nil {
		return shim.Error("Failed to get state for" + keyString)
	}

	if resultValueBytes == nil {
		return shim.Error("Failed to get state for" + keyString)
	}

	return shim.Success(resultValueBytes)
}

Start the chaincode process and listen for incoming endorsement requests

func main() {
	err := shim.Start(new(SimpleChaincode))
	if err != nil {
		fmt.Printf("Error starting Simple chaincode: %s", err)
	}
}

Managing external dependencies for chaincode written in Go

If your chaincode requires packages not provided by the Go standard library, you will need to include those packages with your chaincode. It is also a good practice to add the shim and any extension libraries to your chaincode as a dependency.

There are many tools available for managing (or “vendoring”) these dependencies. The following demonstrates how to use govendor:

govendor init
govendor add +external  // Add all external package, or
govendor add github.com/external/pkg // Add specific external package

This imports the external dependencies into a local vendor directory. If you are vendoring the Fabric shim or shim extensions, clone the Fabric repository to your $GOPATH/src/github.com/hyperledger directory, before executing the govendor commands.

Local environment test

bezant-chaincode-test-network link