前面废话不多说了，链码是什么懂的都懂
资产转移链码
这个应用是一个基础的样例链码，这个链码可以产生一个账本（这个账本能创建资产，读，更新，删除资产，检查是否一个资产存在，转移资产）
为你的代码选个位置
就在home目录下面创建即可，并建立链码go文件（到时候把代码放进去）
// atcc is shorthand for asset transfer chaincode
mkdir atcc && cd atcc
go mod init atcc
touch atcc.go
接下来是构建链码的几个模块函数
内务处理（housekeeping）
也就是给链码输入进一些必要的依赖
我们输入fabric合约api的包并且定义我们的samrtcontract
导入链码依赖包：
package main
import (
"fmt"
"log"
"github.com/hyperledger/fabric-contract-api-go/contractapi"
)
// SmartContract provides functions for managing an Asset（智能合约提供的为了管理资产的函数）
type SmartContract struct {
contractapi.Contract
}
接下来，添加一个结构Asset来表示在账本上的简单的资产
// Asset describes basic details of what makes up a simple asset
type Asset struct {
ID string `json:"ID"`
Color string `json:"color"`
Size int `json:"size"`
Owner string `json:"owner"`
AppraisedValue int `json:"appraisedValue"`
}
建立链码
用InitLedger函数来让账本有些基础数据
// InitLedger adds a base set of assets to the ledger（这个函数把一系列基础的资产加入到账本）
func (s *SmartContract) InitLedger(ctx contractapi.TransactionContextInterface) error {
assets := []Asset{
{
ID: "asset1", Color: "blue", Size: 5, Owner: "Tomoko", AppraisedValue: 300},
{
ID: "asset2", Color: "red", Size: 5, Owner: "Brad", AppraisedValue: 400},
{
ID: "asset3", Color: "green", Size: 10, Owner: "Jin Soo", AppraisedValue: 500},
{
ID: "asset4", Color: "yellow", Size: 10, Owner: "Max", AppraisedValue: 600},
{
ID: "asset5", Color: "black", Size: 15, Owner: "Adriana", AppraisedValue: 700},
{
ID: "asset6", Color: "white", Size: 15, Owner: "Michel", AppraisedValue: 800},
}
for _, asset := range assets {
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
err = ctx.GetStub().PutState(asset.ID, assetJSON)
if err != nil {
return fmt.Errorf("failed to put to world state. %v", err)
}
}
return nil
}
接下来写个函数来在账本上面创造一个还不存在的资产。写链码的时候，检查一下在账本上存在那些东西比直接操作要好。
// CreateAsset issues a new asset to the world state with given details.（函数发布一个新的资产到世界状态）
func (s *SmartContract) CreateAsset(ctx contractapi.TransactionContextInterface, id string, color string, size int, owner string, appraisedValue int) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if exists {
return fmt.Errorf("the asset %s already exists", id)
}
asset := Asset{
ID: id,
Color: color,
Size: size,
Owner: owner,
AppraisedValue: appraisedValue,
}
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
return ctx.GetStub().PutState(id, assetJSON)
}
删除函数
// DeleteAsset deletes an given asset from the world state.
func (s *SmartContract) DeleteAsset(ctx contractapi.TransactionContextInterface, id string) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if !exists {
return fmt.Errorf("the asset %s does not exist", id)
}
return ctx.GetStub().DelState(id)
}
之前提到写链码的时候，检查一下在账本上存在那些东西比直接操作要好，所以这边介绍AssetExists函数来实现。
// AssetExists returns true when asset with given ID exists in world state
func (s *SmartContract) AssetExists(ctx contractapi.TransactionContextInterface, id string) (bool, error) {
assetJSON, err := ctx.GetStub().GetState(id)
if err != nil {
return false, fmt.Errorf("failed to read from world state: %v", err)
}
return assetJSON != nil, nil
}
最后还有两个函数不介绍了，在后面总和代码里面有
下面就是提供代码。如果要看看他是怎么样的，你可以看在fabric-samples文件夹里面的asset-transfer Go chaincode。如果你看assetTransfer.go文件，你能看出他包含package main并且输入在smartcontract.go里面定义的package chaincode，位置在fabric-samples/asset-transfer-basic/chaincode-go/chaincode/.
总和
最后我们需要添加main函数，这个叫 ContractChaincode.Start函数。下面是源码：
package main
import (
"encoding/json"
"fmt"
"log"
"github.com/hyperledger/fabric-contract-api-go/contractapi"
)
// SmartContract provides functions for managing an Asset
type SmartContract struct {
contractapi.Contract
}
// Asset describes basic details of what makes up a simple asset
type Asset struct {
ID string `json:"ID"`
Color string `json:"color"`
Size int `json:"size"`
Owner string `json:"owner"`
AppraisedValue int `json:"appraisedValue"`
}
// InitLedger adds a base set of assets to the ledger
func (s *SmartContract) InitLedger(ctx contractapi.TransactionContextInterface) error {
assets := []Asset{
{
ID: "asset1", Color: "blue", Size: 5, Owner: "Tomoko", AppraisedValue: 300},
{
ID: "asset2", Color: "red", Size: 5, Owner: "Brad", AppraisedValue: 400},
{
ID: "asset3", Color: "green", Size: 10, Owner: "Jin Soo", AppraisedValue: 500},
{
ID: "asset4", Color: "yellow", Size: 10, Owner: "Max", AppraisedValue: 600},
{
ID: "asset5", Color: "black", Size: 15, Owner: "Adriana", AppraisedValue: 700},
{
ID: "asset6", Color: "white", Size: 15, Owner: "Michel", AppraisedValue: 800},
}
for _, asset := range assets {
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
err = ctx.GetStub().PutState(asset.ID, assetJSON)
if err != nil {
return fmt.Errorf("failed to put to world state. %v", err)
}
}
return nil
}
// CreateAsset issues a new asset to the world state with given details.
func (s *SmartContract) CreateAsset(ctx contractapi.TransactionContextInterface, id string, color string, size int, owner string, appraisedValue int) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if exists {
return fmt.Errorf("the asset %s already exists", id)
}
asset := Asset{
ID: id,
Color: color,
Size: size,
Owner: owner,
AppraisedValue: appraisedValue,
}
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
return ctx.GetStub().PutState(id, assetJSON)
}
// ReadAsset returns the asset stored in the world state with given id.
func (s *SmartContract) ReadAsset(ctx contractapi.TransactionContextInterface, id string) (*Asset, error) {
assetJSON, err := ctx.GetStub().GetState(id)
if err != nil {
return nil, fmt.Errorf("failed to read from world state: %v", err)
}
if assetJSON == nil {
return nil, fmt.Errorf("the asset %s does not exist", id)
}
var asset Asset
err = json.Unmarshal(assetJSON, &asset)
if err != nil {
return nil, err
}
return &asset, nil
}
// UpdateAsset updates an existing asset in the world state with provided parameters.
func (s *SmartContract) UpdateAsset(ctx contractapi.TransactionContextInterface, id string, color string, size int, owner string, appraisedValue int) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if !exists {
return fmt.Errorf("the asset %s does not exist", id)
}
// overwriting original asset with new asset
asset := Asset{
ID: id,
Color: color,
Size: size,
Owner: owner,
AppraisedValue: appraisedValue,
}
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
return ctx.GetStub().PutState(id, assetJSON)
}
// DeleteAsset deletes an given asset from the world state.
func (s *SmartContract) DeleteAsset(ctx contractapi.TransactionContextInterface, id string) error {
exists, err := s.AssetExists(ctx, id)
if err != nil {
return err
}
if !exists {
return fmt.Errorf("the asset %s does not exist", id)
}
return ctx.GetStub().DelState(id)
}
// AssetExists returns true when asset with given ID exists in world state
func (s *SmartContract) AssetExists(ctx contractapi.TransactionContextInterface, id string) (bool, error) {
assetJSON, err := ctx.GetStub().GetState(id)
if err != nil {
return false, fmt.Errorf("failed to read from world state: %v", err)
}
return assetJSON != nil, nil
}
// TransferAsset updates the owner field of asset with given id in world state.
func (s *SmartContract) TransferAsset(ctx contractapi.TransactionContextInterface, id string, newOwner string) error {
asset, err := s.ReadAsset(ctx, id)
if err != nil {
return err
}
asset.Owner = newOwner
assetJSON, err := json.Marshal(asset)
if err != nil {
return err
}
return ctx.GetStub().PutState(id, assetJSON)
}
// GetAllAssets returns all assets found in world state
func (s *SmartContract) GetAllAssets(ctx contractapi.TransactionContextInterface) ([]*Asset, error) {
// range query with empty string for startKey and endKey does an
// open-ended query of all assets in the chaincode namespace.
resultsIterator, err := ctx.GetStub().GetStateByRange("", "")
if err != nil {
return nil, err
}
defer resultsIterator.Close()
var assets []*Asset
for resultsIterator.HasNext() {
queryResponse, err := resultsIterator.Next()
if err != nil {
return nil, err
}
var asset Asset
err = json.Unmarshal(queryResponse.Value, &asset)
if err != nil {
return nil, err
}
assets = append(assets, &asset)
}
return assets, nil
}
func main() {
assetChaincode, err := contractapi.NewChaincode(&SmartContract{
})
if err != nil {
log.Panicf("Error creating asset-transfer-basic chaincode: %v", err)
}
if err := assetChaincode.Start(); err != nil {
log.Panicf("Error starting asset-transfer-basic chaincode: %v", err)
}
}
为链码管理外部依赖
你的go 链码依赖于go包，这个不是标准包里面的一部分。这些源一定要在你的链码包里当被安装到一个peer节点上。如果你已经把你的链码作为一个模块，首要做的是就是搞个依赖：
go mod tidy
go mod vendor
这样就把外部依赖放入一个本地的vendor目录
我的步骤
我在home新建了atcc文件夹，把依赖放进去，打入
peer lifecycle chaincode package atcc.tar.gz --path ../atcc/ --lang golang --label atcc_1.0
产生压缩包，并把压缩包复制到test-network文件夹
搭建环境
xport CORE_PEER_TLS_ENABLED=true
export CORE_PEER_LOCALMSPID="Org1MSP"
export CORE_PEER_TLS_ROOTCERT_FILE=${
PWD}/organizations/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt
export CORE_PEER_MSPCONFIGPATH=${
PWD}/organizations/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp
export CORE_PEER_ADDRESS=localhost:7051
在test-network目录下输入：
peer lifecycle chaincode install atcc.tar.gz
接下来什么调用什么都不用再说了，第一篇博客里面有，基本上能安装，其他都好说
而且其实这个代码就是chaincode-go里面的smartcontract