每个链码都需要实现一下 Chaincode 接口
Chaincode接口
type Chaincode interface {
Init(stub shim.ChaincodeStubInterface) peer.Response
Invoke(stub shim.ChaincodeStubInterface) peer.Response
}
Init: 当链码实例化或者升级的时候，Init方法会被调用
Invoke: 当链码收到调用(invoke)或者查询的时候，Invoke 会被调用
链码的基本结构
package main
// 引入相应的依赖包
import (
"fmt"
"github.com/hyperledger/fabric/core/chaincode/shim"
"github.com/hyperledger/fabric/protos/peer"
)
type SimpleChaincode struct {
}
// 链码实例化（instantiate）或 升级（upgrade）时调用 Init 方法
func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) peer.Response{
return shim.Success(nil)
}
// 链码收到调用（invoke） 或 查询 （query）时调用 Invoke 方法
func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
return shim.Success(nil)
}
// 主函数 ，调用 shim.Start 方法
func main() {
err := shim.Start(new(SimpleChaincode))
if( err!= nil) {
fmt.Printf("Error starting Simple Chaincode is %s \n",err)
}
}
链码通过 shim.ChaincodeStubInterface提供的方法来读取和修改账本状态。
helloworld
- 初始化的时候，给 str 赋值 helloworld
- 查询 str 当前的值
- 重新设置 str 的值
- 再次查询 str 的值
package main
import(
"fmt"
"github.com/hyperledger/fabric/core/chaincode/shim"
"github.com/hyperledger/fabric/protos/peer"
)
type Helloworld struct {
}
func (t *Helloworld) Init(stub shim.ChaincodeStubInterface) peer.Response {
fmt.Println("helloworld init")
args := stub.GetStringArgs()
err := stub.PutState(args[0],[]byte(args[1]))
if err != nil {
shim.Error(fmt.Sprintf("helloworld init err %s",err))
}
return shim.Success(nil)
}
func (t *Helloworld) Invoke(stub shim.ChaincodeStubInterface) peer.Response {
fn,args := stub.GetFunctionAndParameters()
var result string
var err error
if fn == "set" {
result,err = set(stub,args)
} else {
result,err = get(stub,args)
}
if err != nil {
shim.Error(err.Error())
}
return shim.Success([]byte(result))
}
func set (stub shim.ChaincodeStubInterface, args []string) (string,error){
fmt.Println("helloworld set")
err := stub.PutState(args[0],[]byte(args[1]))
if err != nil {
return "", fmt.Errorf("Failed to set asset: %s", args[0])
}
return args[0],nil
}
func get(stub shim.ChaincodeStubInterface, args []string) (string,error){
value, err := stub.GetState(args[0])
if err != nil {
return "", fmt.Errorf("Failed to get asset: %s", args[0])
}
if value == nil {
return "", fmt.Errorf("Asset not found: %s", args[0])
}
return string(value),nil
}
func main() {
err := shim.Start(new(Helloworld))
if err != nil {
fmt.Printf("shim start err %s",err)
}
}
helloworld_test.go
package main
import (
"fmt"
"testing"
"github.com/hyperledger/fabric/core/chaincode/shim"
)
func checkInit(t *testing.T, stub *shim.MockStub, args [][]byte) {
res := stub.MockInit("1", args)
if res.Status != shim.OK {
fmt.Println("Init failed", string(res.Message))
t.FailNow()
}
}
func checkQuery(t *testing.T, stub *shim.MockStub, name string) {
res := stub.MockInvoke("1", [][]byte{[]byte("get"), []byte(name)})
if res.Status != shim.OK {
fmt.Println("Query", name, "failed", string(res.Message))
t.FailNow()
}
if res.Payload == nil {
fmt.Println("Query", name, "failed to get value")
t.FailNow()
}
fmt.Println("Query value", name, "was ", string(res.Payload))
}
func checkInvoke(t *testing.T, stub *shim.MockStub, args [][]byte) {
res := stub.MockInvoke("1", args)
if res.Status != shim.OK {
fmt.Println("Invoke", args, "failed", string(res.Message))
t.FailNow()
}
}
func Test_Helloworld(t *testing.T) {
hello := new(Helloworld)
stub := shim.NewMockStub("hello", hello)
checkInit(t, stub, [][]byte{[]byte("str"), []byte("helloworld")})
checkQuery(t, stub, "str")
checkInvoke(t, stub, [][]byte{[]byte("set"), []byte("str"), []byte("helloworld-1111")})
checkQuery(t, stub, "str")
}
通过 go test -v helloworld_test.go helloworld.go 测试相应的方法，运行结果：
=== RUN Test_Helloworld
helloworld init
Query value str was helloworld
helloworld set
Query value str was helloworld-1111
--- PASS: Test_Helloworld (0.00s)
PASS
ok command-line-arguments 0.028s