实战：区块链hyperledger fabric 初体验 - 3： 链码实例安装、实例化、调用及代码

本文链码实例为Fabric 官方实例examples/chaincode/go/chaincode_example02，实现简单的转账功能

进入到cli容器里面

$ docker exec -it fabric-cli bash

１. 链码安装

以在org1, peer0 为例

1.1 设置环境变量

export CORE_PEER_LOCALMSPID=Org2MSP export CORE_PEER_ADDRESS=peer1.org2.example.com:7051 export CORE_PEER_MSPCONFIGPATH=/etc/hyperledger/fabric/crypto-config/peerOrganizations/org2.example.com/users/[email protected]/msp export CORE_PEER_TLS_ROOTCERT_FILE=/etc/hyperledger/fabric/crypto-config/peerOrganizations/org2.example.com/peers/peer1.org2.example.com/tls/ca.crt

1.2 安装链码

＃　peer chaincode install -n test02 -v 1.0 -p examples/chaincode/go/chaincode_example02

修改相关环境变量和参数，重复步骤1.1 和1.2，在{org1, peer1},{org2, peer0},{org2, peer1}上安装链码

２．链码实例化

以下过程在任意一个节点执行一次就行。

peer chaincode instantiate \ -o orderer.example.com:7050 \ -C "businesschannel"  \ -n test02 \ -v 1.0 \ -c '{"Args":["init","a","100","b","200"]}' \ -P "OR    ('Org1MSP.member','Org2MSP.member')" \ --tls true \ --cafile /etc/hyperledger/fabric/crypto-config/ordererOrganizations/example.com/orderers/orderer.example.com/msp/tlscacerts/tlsca.example.com-cert.pem

３．测试链码

３.1 查询初始值

# peer chaincode query -C "businesschannel" -n "exp02" -c '{"Args":["query","a"]}'

# peer chaincode query -C "businesschannel" -n "exp02" -c '{"Args":["query","b"]}'

3.2 转账：从"a" 的账户转账10到"b" 的账户

peer chaincode invoke \ -o orderer.example.com:7050 \ -C "businesschannel" \ -n "test02" \ -c '{"Args":["invoke","a","b","10"]}' \ --tls true \ --cafile /etc/hyperledger/fabric/crypto-config/ordererOrganizations/example.com/orderers/orderer.example.com/msp/tlscacerts/tlsca.example.com-cert.pem

3.3 查询转账结果

＃　peer chaincode query -C "businesschannel" -n "test02" -c '{"Args":["query","a"]}'

查询另一个节点｛org2,peer1} 的账本

export CORE_PEER_LOCALMSPID=Org2MSP export CORE_PEER_ADDRESS=peer1.org2.example.com:7051 export CORE_PEER_MSPCONFIGPATH=/etc/hyperledger/fabric/crypto-config/peerOrganizations/org2.example.com/users/[email protected]/msp export CORE_PEER_TLS_ROOTCERT_FILE=/etc/hyperledger/fabric/crypto-config/peerOrganizations/org2.example.com/peers/peer1.org2.example.com/tls/ca.cr

结果一致。

４.代码解析

４.1 引入必要的包

import (     "fmt"     "strconv"     "github.com/hyperledger/fabric/core/chaincode/shim"     pb "github.com/hyperledger/fabric/protos/peer" )

  "github.com/hyperledger/fabric/core/chaincode/shim"：shim包提供了链码与账本交互的中间层。

4.2 初始化

func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response { ...... //提取参数     _, args := stub.GetFunctionAndParameters()     var A, B string    // Entities     var Aval, Bval int // Asset holdings ......     // 初始化链码     A = args[0]     Aval, err = strconv.Atoi(args[1]) ...... 　B = args[2]     Bval, err = strconv.Atoi(args[3]) ......     // 把状态写入账本     err = stub.PutState(A, []byte(strconv.Itoa(Aval)))   ......     err = stub.PutState(B, []byte(strconv.Itoa(Bval))) ......     return shim.Success(nil) }

4.3 Inovke方法

获取function值

function, args := stub.GetFunctionAndParameters()

根据function值不同，执行不同的分支处理逻辑。

if function == "invoke" {         // Make payment of X units from A to B         return t.invoke(stub, args)     } else if function == "delete" {         // Deletes an entity from its state         return t.delete(stub, args)     } else if function == "query" {         // the old "Query" is now implemtned in invoke         return t.query(stub, args)     }

query分支

func (t *SimpleChaincode) query(stub shim.ChaincodeStubInterface, args []string) pb.Response { ......    A = args[0]     // 从账本获得状态值     Avalbytes, err := stub.GetState(A) ...... }

invoke分支

func (t *SimpleChaincode) invoke(stub shim.ChaincodeStubInterface, args []string) pb.Response { ...... //从账本获取"a"的值 Avalbytes, err := stub.GetState(A) ...... //从账本获取"b"的值 Bvalbytes, err := stub.GetState(B) ...... //执行转账     Aval = Aval - X     Bval = Bval + X ...... //结果计入账本    err = stub.PutState(A, []byte(strconv.Itoa(Aval))) ...... err = stub.PutState(B, []byte(strconv.Itoa(Bval))) ......}

delete分支

func (t *SimpleChaincode) delete(stub shim.ChaincodeStubInterface, args []string) pb.Response { ...... //删除一个实体 err := stub.DelState(A) }

未完待续......