fabric2.3链码学习小记
最近实验室的项目要部署到fabric2.0以上版本，之前写的都是1.4的链码，现在看2.0版本的链码还是有些不一样的，主要是链码api改了：
下面实例这个链码：
package chaincode
import (
"encoding/json"
"fmt"
"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
}首先这里执行完初始化链码之后：
peer chaincode invoke -o localhost:7050 --ordererTLSHostnameOverride orderer.example.com --tls --cafile "${PWD}/organizations/ordererOrganizations/example.com/orderers/orderer.example.com/msp/tlscacerts/tlsca.example.com-cert.pem" -C mychannel -n basic --peerAddresses localhost:7051 --tlsRootCertFiles "${PWD}/organizations/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt" --peerAddresses localhost:9051 --tlsRootCertFiles "${PWD}/organizations/peerOrganizations/org2.example.com/peers/peer0.org2.example.com/tls/ca.crt" -c '{"function":"InitLedger","Args":[]}'这里记住一个模板：
就是peer chiancode invoke ....... -c '{"function":"函数名","Args":[参数]}'
function就是我们链码里的函数名！
2.0的链码是不需要初始化链码的，1.4版本的是需要的，这里2.0的就按照上面的模板就行，注意，参数这里不管链码里传入上面参数，这里都是用字符串格式，比如，int的4也要写成"4"。
注意，如果你想继续用的1.4的链码也可以，将1.4链码原来的包改成这样就可以在2.0环境中继续使用了！
如果你想使用2.0以上版本的链码，需要用的是这个api：
这里注意，2.0的链码，传参数的时候是不能使用args []string的，如果是1.4的链码是可以的。
这里注意，如果想在2.0链码环境中使用如1.4的传入多个参数 args []string的话，可以用这个api：
function, args := ctx.GetStub().GetFunctionAndParameters()
这里注意，这里的function就是Testargs，后面args直接传入4个args参数即可！
根据返回的args，就是之前在1.4环境中的args！
贴上自己写的链码方法demo：
//-c '{"function":"Testargs","Args":["01","fanwen","dayang","man"]}'
//这里注意args后面传入的参数就是args，function是不需要传入的，不然就会报错"err! number is not 4!"，这里是和1.4不一样的地方
func (t *mycc) Testargs(ctx contractapi.TransactionContextInterface) string{
function, args := ctx.GetStub().GetFunctionAndParameters()//这里的function就是获取了上面的函数名就是Testargs
if len(args) != 4 {
return "err! number is not 4!"
}
stu := Student{
StuId: args[0],
Name: args[1],
Address: args[2],
Sex: args[3],
}
assetJSON, err := json.Marshal(stu)
if err != nil {
return err.Error()
}
//根据StuId存入账本
err = ctx.GetStub().PutState(stu.StuId, assetJSON)
if err != nil{
return err.Error()
}
return "you use the function:" + function + " put in state ok!"
}执行效果：
如果在args输入了超过4个参数：
就会报错，就是我们在链码里自己写的逻辑判断的错误！
这里注意，fabric在2.0版本以上的链码中，可以返回任何数据！比如string,int,float64,或者是自定义的结构体或者结构体指针都可以！
注意：传参数的时候，不管传什么参数，在cli端，都是传入的"内容"，也就是字符串形式传入的！
如果是查询操作的话，不需要连接orderer结点，也不需要背书策略，直接用以下模板就行：
peer chaincode query -C mychannel -n fan12 -c '{"function":"GetAll","Args":["args"]}'
当然，如果用invoke也可以！看个人习惯。