Experience sharing on building blockchain distributed applications using Go language

Experience sharing of writing blockchain distributed applications in Go language: Deploy blockchain network: Use frameworks such as Fabric to generate configuration files and certificates to create your own blockchain network. Create smart contracts: Use the Go standard library to write immutable smart contracts and define contract logic and interaction methods. Connect to the blockchain network: Use the Go SDK to connect to the blockchain network, interact with smart contracts, send transactions and query data. Practical case: Taking the voting system as an example, it shows how to use Go to build a decentralized application and securely store votes in hash form on the blockchain.

Experience sharing in building blockchain distributed applications using Go language

Today with the booming development of blockchain technology, Go With its efficient and concurrent features, the language has become an ideal choice for building blockchain distributed applications. This article will share my experience in developing blockchain applications using Go language, and provide practical cases to help you get started easily.

Deploying Blockchain Network

Using popular blockchain frameworks such as Fabric, we can easily create our own blockchain network. Fabric provides a series of tools, such as configtxgen and cryptogen, to help you generate the necessary configuration files and certificates.

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

Creating smart contracts

Smart contracts are immutable programs on the blockchain. Go language provides a rich standard library to easily write smart contracts.

// 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)
    }
}

Connecting to the blockchain network

Clients can use the Go SDK to connect to the blockchain network and interact with smart contracts.

// 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)
}

Practical Case: Voting System

Using the Go language, we can build a decentralized voting system where votes are stored in a secure hash in the district on the blockchain.

// 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
}

Conclusion

Go language provides strong support for building blockchain distributed applications with its efficiency, concurrency and complete standard library. Through practical cases, we show how to use Go language to write smart contracts, interact with blockchain networks, and build practical applications. As blockchain technology continues to develop, the Go language will continue to play a vital role.

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