Netkiller Blockchain 手札

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Mr. Neo Chan, 陈景峯(BG7NYT)

中国广东省深圳市望海路半岛城邦三期
518067
+86 13113668890

<netkiller@msn.com>

文档始创于2018-02-10

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2.10.6. 资产上链的 Hyperledger Fabic 链码

我们希望资产上链适用于任何领域，后面也方便将业务拓展。所以我实现了一个万能合约。以不变应万变。

package mainimport ("fmt""github.com/hyperledger/fabric/core/chaincode/shim"pb "github.com/hyperledger/fabric/protos/peer"
)type SmartContract struct {}func (s *SmartContract) Init(stub shim.ChaincodeStubInterface) pb.Response {return shim.Success(nil)
}func (s *SmartContract) Query(stub shim.ChaincodeStubInterface) pb.Response {return shim.Success(nil)
}func (s *SmartContract) Invoke(stub shim.ChaincodeStubInterface) pb.Response {// Retrieve the requested Smart Contract function and argumentsfunction, args := stub.GetFunctionAndParameters()// Route to the appropriate handler function to interact with the ledger appropriatelyif function == "create" {return s.create(stub, args)} else if function == "find" {return s.find(stub, args)} else if function == "update" {return s.update(stub, args)} else if function == "delete" {return s.delete(stub, args)}return shim.Error("Invalid Smart Contract function name.")
}func (s *SmartContract) create(stub shim.ChaincodeStubInterface, args []string) pb.Response {if len(args) != 2 {return shim.Error("Incorrect number of arguments. Expecting 2")}_key    := args[0]_data    := args[1]if(_data == ""){return shim.Error("Incorrect string of data")}existAsBytes,err := stub.GetState(_key)if string(existAsBytes) != "" {fmt.Println("Failed to create account, Duplicate key.")return shim.Error("Failed to create account, Duplicate key.")}err = stub.PutState(_key, []byte(_data))if err != nil {return shim.Error(err.Error())}fmt.Printf("create %s %s \n", _key, string(_data))return shim.Success(nil)
}func (s *SmartContract) find(stub shim.ChaincodeStubInterface, args []string) pb.Response {if len(args) != 1 {return shim.Error("Incorrect number of arguments. Expecting 1")}_key      := args[0]_data, err := stub.GetState(_key)if err != nil {return shim.Error(err.Error())}if string(_data) == "" {return shim.Error("The key isn't exist.")}else{fmt.Printf("query %s %s \n", _key, string(_data))}return shim.Success(_data)
}func (s *SmartContract) update(stub shim.ChaincodeStubInterface, args []string) pb.Response {if len(args) != 2 {return shim.Error("Incorrect number of arguments. Expecting 2")}_key    := args[0]_data    := args[1]if(_data == ""){return shim.Error("Incorrect string of data")}err := stub.PutState(_key, []byte(_data))if err != nil {return shim.Error(err.Error())}else{fmt.Printf("update %s %s \n", _key, string(_data))}return shim.Success(nil)
}// Deletes an entity from state
func (t *SmartContract) delete(stub shim.ChaincodeStubInterface, args []string) pb.Response {if len(args) != 1 {return shim.Error("Incorrect number of arguments. Expecting 1")}_key := args[0]// Delete the key from the state in ledgererr := stub.DelState(_key)if err != nil {return shim.Error("Failed to delete state")}return shim.Success(nil)
}func main() {err := shim.Start(new(SmartContract))if err != nil {fmt.Printf("Error creating new Smart Contract: %s", err)}
}

链码有四个函数，分别是创建，查找，更新，删除。

if function == "create" {return s.create(stub, args)        // 创建} else if function == "find" {return s.find(stub, args)        // 查找} else if function == "update" {return s.update(stub, args)        // 更新} else if function == "delete" {return s.delete(stub, args)        // 删除}

上链使用 create 方法，函数有两个参数，一个是 key, 另一个是数据。

key 使用 UUID 存储再数据库和链上，同时 UUID 对应通证的

data 是序列化 byte 数据。例如可以使用 json, hession, msgpack 等序列化后的数据。

err = stub.PutState(_key, []byte(_data))

这个链码考虑到前期产品上市，不确定性因素很多，需要更新和删除等等。后期我们可以在数据中设置一个 status 变量，当 status = false 就不在允许数据的删除和更新。