链码安装和实例化之后就可以调用chaincode执行交易，下面分析简单的账户转账操作是如何完成的。
源码分析
1.首先看app.js的路由函数
app.post('/channels/:channelName/chaincodes/:chaincodeName', async function(req, res) {
var peers = req.body.peers;
var chaincodeName = req.params.chaincodeName;
var channelName = req.params.channelName;
var fcn = req.body.fcn;
var args = req.body.args;
// 此处省略了参数校验
let message = await invoke.invokeChaincode(peers, channelName, chaincodeName, fcn, args, req.username, req.orgname);
res.send(message);
});2.接下来找到
var invokeChaincode = async function(peerNames, channelName, chaincodeName, fcn, args, username, org_name) {
var error_message = null;
var tx_id_string = null;
try {
var client = await helper.getClientForOrg(org_name, username); // 创建client对象
var channel = client.getChannel(channelName); // 创建channel对象
// 获取交易id：基于client对象上分配的用户身份（_userContext）
var tx_id = client.newTransactionID();
tx_id_string = tx_id.getTransactionID();
// 请求结构
var request = {
targets: peerNames,
chaincodeId: chaincodeName,
fcn: fcn,
args: args,
chainId: channelName,
txId: tx_id
};
// SDK根据request生成proposal，并调用sendPeersProposal()
// 将提案发送给背书节点，然后将返回的提案响应连同交易提案一起打包返回给client
let results = await channel.sendTransactionProposal(request);
// 返回的交易提案和提案响应
var proposalResponses = results[0];
var proposal = results[1];
// 检查提案响应是否正确
var all_good = true;
for (var i in proposalResponses) {
let one_good = false;
if (proposalResponses && proposalResponses[i].response &&
proposalResponses[i].response.status === 200) {
one_good = true;
logger.info('invoke chaincode proposal was good');
} else {
logger.error('invoke chaincode proposal was bad');
}
all_good = all_good & one_good;
}
if (all_good) {
var promises = [];
// 基于channel的事件中心
let event_hubs = channel.getChannelEventHubsForOrg();
#event_hubs.forEach((eh) => {
#let invokeEventPromise = new Promise((resolve, reject) => {
#let event_timeout = setTimeout(() => {
let message = 'REQUEST_TIMEOUT:' + eh.getPeerAddr();
logger.error(message);
eh.disconnect();
}, 3000);
// 注册交易事件监听，当交易被peer提交到账本中时可以得到反馈
#eh.registerTxEvent(tx_id_string, (tx, code, block_num) => {
clearTimeout(event_timeout);
}, (err) => {
clearTimeout(event_timeout);
logger.error(err);
reject(err);
},
{unregister: true, disconnect: true}
);
eh.connect();
});
promises.push(invokeEventPromise);
});
// 将txID，交易提案和提案响应打包成交易请求
var orderer_request = {
txId: tx_id,
proposalResponses: proposalResponses,
proposal: proposal
};
// 将交易请求发送给orderer节点，内部调用sendBroadcast(envelope)
var sendPromise = channel.sendTransaction(orderer_request);
promises.push(sendPromise);
let results = await Promise.all(promises);
let response = results.pop();
if (response.status === 'SUCCESS') {
logger.info('Successfully sent transaction to the orderer.');
} else {
error_message = util.format('Failed to order the transaction. Error code: %s',response.status);
logger.debug(error_message);
}
} else {
error_message = util.format('Failed to send Proposal and receive all good ProposalResponse');
logger.debug(error_message);
}
} catch (error) {
logger.error('Failed to invoke due to error: ' + error.stack ? error.stack : error);
error_message = error.toString();
}
if (!error_message) {
// 返回交易id
return tx_id_string;
} else {
let message = util.format('Failed to invoke chaincode. cause:%s',error_message);
logger.error(message);
throw new Error(message);
}
};3.如果我们进行简单的转账交易 A->B，则需要调用链码中的move方法，代码如下：
func (t *SimpleChaincode) move(stub shim.ChaincodeStubInterface, args []string) pb.Response {
// 两个账户A，B
var A, B string
// 账户的余额数
var Aval, Bval int
// 转移的数值
var X int
var err error
if len(args) != 3 {
return shim.Error("Incorrect number of arguments. Expecting 4, function followed by 2 names and 1 value")
}
A = args[0]
B = args[1]
// 获取账户A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")
}
Aval, _ = strconv.Atoi(string(Avalbytes))
// 获取账户B的值
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))
X, err = strconv.Atoi(args[2])
if err != nil {
return shim.Error("Invalid transaction amount, expecting a integer value")
}
// 余额转移计算
Aval = Aval - X
Bval = Bval + X
logger.Infof("Aval = %d, Bval = %d\n", Aval, Bval)
// 将改变后的值写入状态数据库中
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);
}测试
交易：
curl -s -X POST \
http://localhost:4000/channels/mychannel/chaincodes/mycc \
-H "authorization: Bearer " \
-H "content-type: application/json" \
-d '{
"peers": ["peer0.org1.example.com","peer1.org1.example.com"],
"fcn":"move",
"args":["a","b","10"]
}'结果：
Transacton ID is 970928c6acbae452a43cbc59e1cb9a558a09c4f354cda0025bd51dafcca3ad96