使用Go语言构建区块链分布式应用的经验分享

// 使用 cryptogen 生成 CA 证书密钥
cryptogen generate --output ./crypto-config --config ./crypto-config.yaml

// 简单的 Go 智能合约
package main

import (
    "encoding/json"
    "fmt"

    "github.com/hyperledger/fabric-contract-api-go/contractapi"
)

// SmartContract 定义智能合约
type SmartContract struct {
    contractapi.Contract
}

// Init 初始化合约
func (s *SmartContract) Init(ctx contractapi.TransactionContextInterface) error {
    return nil
}

// Invoke 调用合约方法
func (s *SmartContract) Invoke(ctx contractapi.TransactionContextInterface) error {
    function, args := ctx.GetStub().GetFunctionAndParameters()

    switch function {
    case "set":
        if len(args) != 2 {
            return fmt.Errorf("invaild number of arguments")
        }

        key, value := args[0], args[1]
        err := ctx.GetStub().PutState(key, []byte(value))
        if err != nil {
            return err
        }

    case "get":
        if len(args) != 1 {
            return fmt.Errorf("invaild number of arguments")
        }

        key := args[0]
        value, err := ctx.GetStub().GetState(key)
        if err != nil {
            return err
        }

        fmt.Println(string(value))

    default:
        return fmt.Errorf("unknown function")
    }

    return nil
}

func main() {
    chaincode, err := contractapi.NewChaincode(new(SmartContract))
    if err != nil {
        fmt.Println("Error creating chaincode: ", err)
    }

    server := &contractapi.Server{
        Chaincode: chaincode,
    }

    if err := server.Start(); err != nil {
        fmt.Println("Error starting gRPC server: ", err)
    }
}

// 连接到区块链网络
client, err := fabric.NewClient(client.Config{})
if err != nil {
    fmt.Println("Error connecting to fabric network: ", err)
}

// 通过合约名称和方法对智能合约进行调用
response, err := client.InvokeChaincode(fab.ChaincodeInvocationSpec{
    ChaincodeName: "mychaincode",
    ChaincodeSpec:  chaincode.ChaincodeSpec{Type: chaincode.GOLANG},
    MethodName:    "set",
    Args:          [][]byte{[]byte("key1"), []byte("value1")},
})

if err != nil {
    fmt.Println("Error invoking chaincode: ", err)
} else {
    fmt.Println("Invoke response: ", response)
}

// 投票系统合约
type VotingContract struct {
    contractapi.Contract
}

// 投票
func (v *VotingContract) Vote(ctx contractapi.TransactionContextInterface, candidate string) error {
    voter := ctx.GetClientIdentity().GetID()
    votedCandidates, err := ctx.GetStub().GetState(voter)
    if err != nil {
        return err
    }

    if len(votedCandidates) > 0 {
        return fmt.Errorf("you have already voted")
    }

    candidates, err := ctx.GetStub().GetState("candidates")
    if err != nil {
        return err
    }

    candidatesMap := map[string]int{}
    json.Unmarshal(candidates, &candidatesMap)
    candidatesMap[candidate]++
    candidatesBytes, err := json.Marshal(candidatesMap)
    if err != nil {
        return err
    }

    err = ctx.GetStub().PutState("candidates", candidatesBytes)
    if err != nil {
        return err
    }

    votedCandidates = append(votedCandidates, []byte(candidate)...)
    err = ctx.GetStub().PutState(voter, votedCandidates)
    if err != nil {
        return err
    }

    return nil
}

// 获取候选人
func (v *VotingContract) GetCandidates(ctx contractapi.TransactionContextInterface) ([]string, error) {
    candidates, err := ctx.GetStub().GetState("candidates")
    if err != nil {
        return nil, err
    }

    candidatesMap := map[string]int{}
    json.Unmarshal(candidates, &candidatesMap)

    candidatesList := []string{}
    for candidate := range candidatesMap {
        candidatesList = append(candidatesList, candidate)
    }

    return candidatesList, nil
}