Fabric-小例子

汽車資訊記錄

汽車資訊的鏈碼結構
1、引入依賴包

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"strconv"

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

2、宣告一個結構體

type SimpleChaincode struct {
}

3、宣告Init() 和 Invoke() 函式

// 在鏈碼初始化程序中呼叫 Init 來資料，此處不做任何操作
func (s *SmartContract) Init(APIstub shim.ChaincodeStubInterface) sc.Response {
	return shim.Success(nil)
}

// query 和 invoke 時被自動呼叫
func (s *SmartContract) Invoke(APIstub shim.ChaincodeStubInterface) sc.Response {

	// 決議用戶呼叫鏈碼傳遞的函式名及引數
	function, args := APIstub.GetFunctionAndParameters()
	
	// 呼叫不同的函式
	if function == "queryCar" { 
		return s.queryCar(APIstub, args)   
	} else if function == "initLedger" {
		return s.initLedger(APIstub)
	} else if function == "createCar" {
		return s.createCar(APIstub, args)
	} else if function == "queryAllCars" {
		return s.queryAllCars(APIstub)
	} else if function == "changeCarOwner" {
		return s.changeCarOwner(APIstub, args)
	}

	return shim.Error("Invalid Smart Contract function name.")
}

4、對Invoke() 函式中的各個函式就是進行宣告

// 初始化賬本資料
func (s *SmartContract) initLedger(APIstub shim.ChaincodeStubInterface) sc.Response {
	cars := []Car{
		Car{Make: "Toyota", Model: "Prius", Colour: "blue", Owner: "Tomoko"},
		Car{Make: "Ford", Model: "Mustang", Colour: "red", Owner: "Brad"},
		Car{Make: "Hyundai", Model: "Tucson", Colour: "green", Owner: "Jin Soo"},
		Car{Make: "Volkswagen", Model: "Passat", Colour: "yellow", Owner: "Max"},
		Car{Make: "Tesla", Model: "S", Colour: "black", Owner: "Adriana"},
		Car{Make: "Peugeot", Model: "205", Colour: "purple", Owner: "Michel"},
		Car{Make: "Chery", Model: "S22L", Colour: "white", Owner: "Aarav"},
		Car{Make: "Fiat", Model: "Punto", Colour: "violet", Owner: "Pari"},
		Car{Make: "Tata", Model: "Nano", Colour: "indigo", Owner: "Valeria"},
		Car{Make: "Holden", Model: "Barina", Colour: "brown", Owner: "Shotaro"},
	}

	i := 0
	for i < len(cars) {
		fmt.Println("i is ", i)
		carAsBytes, _ := json.Marshal(cars[i])
		// key 為編號 CARi，value 為 Car 結構體的 json 串
		APIstub.PutState("CAR"+strconv.Itoa(i), carAsBytes)
		fmt.Println("Added", cars[i])
		i = i + 1
	}

	return shim.Success(nil)
}

// 根據編號查詢汽車
func (s *SmartContract) queryCar(APIstub shim.ChaincodeStubInterface, args []string) sc.Response {

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

	carAsBytes, _ := APIstub.GetState(args[0])
	return shim.Success(carAsBytes)
}

// 創建一輛新的汽車資料
func (s *SmartContract) createCar(APIstub shim.ChaincodeStubInterface, args []string) sc.Response {

	if len(args) != 5 {
		return shim.Error("Incorrect number of arguments. Expecting 5")
	}

	var car = Car{Make: args[1], Model: args[2], Colour: args[3], Owner: args[4]}

	carAsBytes, _ := json.Marshal(car)
	APIstub.PutState(args[0], carAsBytes)

	return shim.Success(nil)
}

// 查詢全部的汽車
func (s *SmartContract) queryAllCars(APIstub shim.ChaincodeStubInterface) sc.Response {

	// 查詢 startKey（包括）到 endKey（不包括）間的值
	startKey := "CAR0"
	endKey := "CAR999"

	resultsIterator, err := APIstub.GetStateByRange(startKey, endKey)
	if err != nil {
		return shim.Error(err.Error())
	}
	defer resultsIterator.Close()  // 延遲關閉迭代器

	// 將查詢結果以 json 字串的形式寫入 buffer
	var buffer bytes.Buffer
	buffer.WriteString("[")

	bArrayMemberAlreadyWritten := false
	for resultsIterator.HasNext() {
		queryResponse, err := resultsIterator.Next()
		if err != nil {
			return shim.Error(err.Error())
		}
		
		if bArrayMemberAlreadyWritten == true {
			buffer.WriteString(",")
		}
		buffer.WriteString("{\"Key\":")
		buffer.WriteString("\"")
		buffer.WriteString(queryResponse.Key)
		buffer.WriteString("\"")

		buffer.WriteString(", \"Record\":")
		// Record is a JSON object, so we write as-is
		buffer.WriteString(string(queryResponse.Value))
		buffer.WriteString("}")
		bArrayMemberAlreadyWritten = true
	}
	buffer.WriteString("]")

	fmt.Printf("- queryAllCars:\n%s\n", buffer.String())

	return shim.Success(buffer.Bytes())
}

// 根據汽車編號改變車的擁有者
func (s *SmartContract) changeCarOwner(APIstub shim.ChaincodeStubInterface, args []string) sc.Response {

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

	carAsBytes, _ := APIstub.GetState(args[0])
	car := Car{}

	json.Unmarshal(carAsBytes, &car)
	car.Owner = args[1]   // 更改汽車擁有者

	carAsBytes, _ = json.Marshal(car)
	APIstub.PutState(args[0], carAsBytes)  // 更新賬本

	return shim.Success(nil)
}

5、主函式

func main() {
	err := shim.Start(new(SmartContract))
	if err != nil {
		fmt.Printf("Error creating new Smart Contract: %s", err)
	}
}

PS：shim.Start() 中 的SmartContract 是上面宣告的結構體

將該鏈碼放于./fabric/fabric-samples/chaincode/car/go/
接下來我們啟動本地測驗網路

$ docker-compose -f docker-compose-simple.yaml up -d

docker-compose-simple.yaml檔案一般是位于/fabric/fabric-samples/chaincode-docker-devmode

進入鏈碼容器，對鏈碼進行編譯

$ docker exec -it chaincode bash
root@61638bc49a3b:/opt/gopath/src/chaincode# cd car
root@61638bc49a3b:/opt/gopath/src/chaincode/car# cd go 
root@61638bc49a3b:/opt/gopath/src/chaincode/car/go# go build

執行成功后當前目錄會生成一個可執行檔案go，此時需要啟動這個可執行檔案.

CORE_PEER_ADDRESS=peer:7052 CORE_CHAINCODE_ID_NAME=test:0 ./go

執行成功后顯示：

這邊為什么用7052埠，是因為peer:7052是用于鏈碼專用監聽地址及埠號，而7051是peer節點監聽的是網路埠號.

2020-10-07 05:35:29.120 UTC [shim] SetupChaincodeLogging -> INFO 001 Chaincode log level not provided; defaulting to: INFO
2020-10-07 05:35:29.120 UTC [shim] SetupChaincodeLogging -> INFO 002 Chaincode (build level: ) starting up ...

打開終端二
進入cli容器中

$ docker exec -it cli bash

查看當前節點加入的通道

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer channel list

顯示結果

Channels peers has joined: 
myc

每一個人的通道不一定一樣的，所有最好檢查一下，

安裝和實體化鏈碼

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer chaincode install -p chaincodedev/chaincode/fabcar/go -n test -v 0

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer chaincode instantiate -n test -v 0 -c '{"Args":[]}' -C myc

初始化資料，呼叫initLedger函式：

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer chaincode invoke -n test -c '{"Args":["initLedger"]}' -C myc

查詢所有汽車的資訊：

root@ef915a1edb32:/opt/gopath/src/chaincodedev#  peer chaincode query -n test -c '{"Args":["queryAllCars"]}' -C myc

[{"Key":"CAR0", "Record":{"make":"Toyota","model":"Prius","colour":"blue","owner":"Tomoko"}},
{"Key":"CAR1", "Record":{"make":"Ford","model":"Mustang","colour":"red","owner":"Brad"}},
{"Key":"CAR2", "Record":{"make":"Hyundai","model":"Tucson","colour":"green","owner":"Jin Soo"}},
{"Key":"CAR3", "Record":{"make":"Volkswagen","model":"Passat","colour":"yellow","owner":"Max"}},
{"Key":"CAR4", "Record":{"make":"Tesla","model":"S","colour":"black","owner":"Adriana"}},
{"Key":"CAR5", "Record":{"make":"Peugeot","model":"205","colour":"purple","owner":"Michel"}},
{"Key":"CAR6", "Record":{"make":"Chery","model":"S22L","colour":"white","owner":"Aarav"}},
{"Key":"CAR7", "Record":{"make":"Fiat","model":"Punto","colour":"violet","owner":"Pari"}},
{"Key":"CAR8", "Record":{"make":"Tata","model":"Nano","colour":"indigo","owner":"Valeria"}},
{"Key":"CAR9", "Record":{"make":"Holden","model":"Barina","colour":"brown","owner":"Shotaro"}}]

創建編號為CAR10的汽車資訊

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer chaincode invoke -n test -c '{"Args":["createCar","CAR10","Toyota","Prius","blue","233"]}' -C myc

查詢編號為CAR10的汽車資訊

root@ef915a1edb32:/opt/gopath/src/chaincodedev# peer chaincode query -n test -c '{"Args":["queryCar","CAR10"]}' -C myc

{"make":"Toyota","model":"Prius","colour":"blue","owner":"233"}

關閉網路：$ docker-compose -f docker-compose-simple.yaml down