智能合约代码分析

在上一篇博客中我们已经简单分析了Fabric启动时日志，接下来我们分析一下script.sh脚本和chaincode的源代码。

进入~/go/src/github.com/hyperledger/fabric-samples/first-network/scripts目录下，找出其中与链码有关的部分：

installChaincode () {
	PEER=$1
	setGlobals $PEER
	peer chaincode install -n mycc -v 1.0 -p github.com/hyperledger/fabric/examples/chaincode/go/chaincode_example02 >&log.txt
	res=$?
	cat log.txt
        verifyResult $res "Chaincode installation on remote peer PEER$PEER has Failed"
	echo "===================== Chaincode is installed on remote peer PEER$PEER ===================== "
	echo
}


instantiateChaincode () {
	PEER=$1
	setGlobals $PEER
	# while 'peer chaincode' command can get the orderer endpoint from the peer (if join was successful),
	# lets supply it directly as we know it using the "-o" option
	if [ -z "$CORE_PEER_TLS_ENABLED" -o "$CORE_PEER_TLS_ENABLED" = "false" ]; then
		peer chaincode instantiate -o orderer.example.com:7050 -C $CHANNEL_NAME -n mycc -v 1.0 -c '{"Args":["init","a","100","b","200"]}' -P "OR	('Org1MSP.member','Org2MSP.member')" >&log.txt
	else
		peer chaincode instantiate -o orderer.example.com:7050 --tls $CORE_PEER_TLS_ENABLED --cafile $ORDERER_CA -C $CHANNEL_NAME -n mycc -v 1.0 -c '{"Args":["init","a","100","b","200"]}' -P "OR	('Org1MSP.member','Org2MSP.member')" >&log.txt
	fi
	res=$?
	cat log.txt
	verifyResult $res "Chaincode instantiation on PEER$PEER on channel '$CHANNEL_NAME' failed"
	echo "===================== Chaincode Instantiation on PEER$PEER on channel '$CHANNEL_NAME' is successful ===================== "
	echo
}


chaincodeQuery () {
  PEER=$1
  echo "===================== Querying on PEER$PEER on channel '$CHANNEL_NAME'... ===================== "
  setGlobals $PEER
  local rc=1
  local starttime=$(date +%s)

  # continue to poll
  # we either get a successful response, or reach TIMEOUT
  while test "$(($(date +%s)-starttime))" -lt "$TIMEOUT" -a $rc -ne 0
  do
     sleep $DELAY
     echo "Attempting to Query PEER$PEER ...$(($(date +%s)-starttime)) secs"
     peer chaincode query -C $CHANNEL_NAME -n mycc -c '{"Args":["query","a"]}' >&log.txt
     test $? -eq 0 && VALUE=$(cat log.txt | awk '/Query Result/ {print $NF}')
     test "$VALUE" = "$2" && let rc=0
  done
  echo
  cat log.txt
  if test $rc -eq 0 ; then
	echo "===================== Query on PEER$PEER on channel '$CHANNEL_NAME' is successful ===================== "
  else
	echo "!!!!!!!!!!!!!!! Query result on PEER$PEER is INVALID !!!!!!!!!!!!!!!!"
        echo "================== ERROR !!! FAILED to execute End-2-End Scenario =================="
	echo
	exit 1
  fi
}


chaincodeInvoke () {
	PEER=$1
	setGlobals $PEER
	# while 'peer chaincode' command can get the orderer endpoint from the peer (if join was successful),
	# lets supply it directly as we know it using the "-o" option
	if [ -z "$CORE_PEER_TLS_ENABLED" -o "$CORE_PEER_TLS_ENABLED" = "false" ]; then
		peer chaincode invoke -o orderer.example.com:7050 -C $CHANNEL_NAME -n mycc -c '{"Args":["invoke","a","b","10"]}' >&log.txt
	else
		peer chaincode invoke -o orderer.example.com:7050  --tls $CORE_PEER_TLS_ENABLED --cafile $ORDERER_CA -C $CHANNEL_NAME -n mycc -c '{"Args":["invoke","a","b","10"]}' >&log.txt
	fi
	res=$?
	cat log.txt
	verifyResult $res "Invoke execution on PEER$PEER failed "
	echo "===================== Invoke transaction on PEER$PEER on channel '$CHANNEL_NAME' is successful ===================== "
	echo
}

接下来我们分析一下各个函数方法：

1、installChaincode ()将区块链进行打包，然后上传到某一个节点上。

2、instantiateChaincode ()将链码初始化，其中

peer chaincode instantiate -o orderer.example.com:7050 -C $CHANNEL_NAME -n mycc -v 1.0 -c '{"Args":["init","a","100","b","200"]}' -P "OR	

调用了我们上一篇博文中所看到的chaincode_example02.go中的init方法,其中init源代码部分如下：

func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response {
        fmt.Println("ex02 Init")
        _, args := stub.GetFunctionAndParameters()
        var A, B string    // Entities
        var Aval, Bval int // Asset holdings
        var err error

        //接受了四个参数  
        if len(args) != 4 {
                return shim.Error("Incorrect number of arguments. Expecting 4")
        }

        // Initialize the chaincode
        //A代表a
        A = args[0]
        //A的value是100
        Aval, err = strconv.Atoi(args[1])
        if err != nil {
                return shim.Error("Expecting integer value for asset holding")
        }
        //B代表b
        B = args[2]
        //b的value是200
        Bval, err = strconv.Atoi(args[3])
        if err != nil {
                return shim.Error("Expecting integer value for asset holding")
        }
        fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)

        // Write the state to the ledger
        err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
        if err != nil {
                return shim.Error(err.Error())
        }

        err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
        if err != nil {
                return shim.Error(err.Error())
        }

        return shim.Success(nil)
}

它创建了a,b两个账户，并分别初始化

3、chaincodeQuery ()代表调用查询方法，其中有这么一句：

peer chaincode query -C $CHANNEL_NAME -n mycc -c '{"Args":["query","a"]}' >&log.txt

它调用了我们上一篇博文中所看到的chaincode_example02.go中的query方法,查询a账户的余额，其中query源代码部分如下：

// query callback representing the query of a chaincode
func (t *SimpleChaincode) query(stub shim.ChaincodeStubInterface, args []string) pb.Response {
        var A string // Entities
        var err error

        if len(args) != 1 {
                return shim.Error("Incorrect number of arguments. Expecting name of the person to query")
        }

        A = args[0]

        // Get the state from the ledger
        Avalbytes, err := stub.GetState(A)
        if err != nil {
                jsonResp := "{\"Error\":\"Failed to get state for " + A + "\"}"
                return shim.Error(jsonResp)
        }

        if Avalbytes == nil {
                jsonResp := "{\"Error\":\"Nil amount for " + A + "\"}"
                return shim.Error(jsonResp)
        }

        jsonResp := "{\"Name\":\"" + A + "\",\"Amount\":\"" + string(Avalbytes) + "\"}"
        fmt.Printf("Query Response:%s\n", jsonResp)
        return shim.Success(Avalbytes)
}

其实就是返回a账户的余额，在上一篇博文的日志输出中，我们也会看到相应的结果，

4、chaincodeInvoke ()方法中中有这样一句话：

peer chaincode invoke -o orderer.example.com:7050 -C $CHANNEL_NAME -n mycc -c '{"Args":["invoke","a","b","10"]}' >&log.txt

它调用了我们上一篇博文中所看到的chaincode_example02.go中的invoke方法,查询a账户的余额，其中invoke源代码部分如下：

// Transaction makes payment of X units from A to B
func (t *SimpleChaincode) invoke(stub shim.ChaincodeStubInterface, args []string) pb.Response {
	var A, B string    // Entities
	var Aval, Bval int // Asset holdings
	var X int          // Transaction value
	var err error
    
    //接收三个参数
	if len(args) != 3 {
		return shim.Error("Incorrect number of arguments. Expecting 3")
	}
    //两个账户的名称
	A = args[0]
	B = args[1]

	//查询两个账户的值
	Avalbytes, err := stub.GetState(A)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Avalbytes == nil {
		return shim.Error("Entity not found")
	}
    //数值转换，在fabric中存的值都是byte数组，我们需要的是整型
	Aval, _ = strconv.Atoi(string(Avalbytes))

	Bvalbytes, err := stub.GetState(B)
	if err != nil {
		return shim.Error("Failed to get state")
	}
	if Bvalbytes == nil {
		return shim.Error("Entity not found")
	}
	Bval, _ = strconv.Atoi(string(Bvalbytes))

	// 把第三个参数赋值给了x
	X, err = strconv.Atoi(args[2])
	if err != nil {
		return shim.Error("Invalid transaction amount, expecting a integer value")
	}
    //转账操作
	Aval = Aval - X
	Bval = Bval + X
	fmt.Printf("Aval = %d, Bval = %d\n", Aval, Bval)

	// Write the state back to the ledger
    //更新账本
	err = stub.PutState(A, []byte(strconv.Itoa(Aval)))
	if err != nil {
		return shim.Error(err.Error())
	}

	err = stub.PutState(B, []byte(strconv.Itoa(Bval)))
	if err != nil {
		return shim.Error(err.Error())
	}
    //返回成功的标致
	return shim.Success(nil)
}

到此源码分析就结束了，具体的内容还需要进一步学习，最后把我们出啊关键的网络给清除了，不影响后续网络的创建。

./byfn.sh -m down -c mychannel