前面的文章都是在讲解Fabric网络的搭建和ChainCode的开发，那么在ChainCode开发完毕后，我们就需要使用Fabric SDK做应用程序的开发了。官方虽然提供了Node.JS，Java，Go，Python等多种语言的SDK，但是由于整个Fabric太新了，很多SDK还不成熟和完善，所以我采用Node JS的SDK，毕竟这个是功能毕竟齐全，而且也是官方示例的时候使用的SDK。由于我从来没有接触过Node.JS的开发，对这个语言理解不深，所以讲的比较肤浅，希望大家见谅。
1.环境准备
Node.js是一个跨平台的语言，可以在Linux，Window和Mac上安装，我们在开发的时候可以在Windows下开发，最后生产环境一般都是Linux，所以我们这里就以Ubuntu为例。Fabric Node SDK支持的Node版本是v6，不支持最新的v8版本。NodeJS官方给我们提供了很方便的安装方法，具体文档在：https://nodejs.org/en/download/package-manager/#debian-and-ubuntu-based-linux-distributions
我们只需要执行以下命令即可安装NodeJS的最新v6版本：
curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
sudo apt-get install -y nodejs
安装完成后我们可以使用以下两个命令来查看安装的Node版本和npm版本。node –v
npm -v
关于NPM，这个是一个包管理器，我觉得很像VS里面的NuGet，关于NPM的基础知识，我们可以参考这篇博客：http://www.ruanyifeng.com/blog/2016/01/npm-install.html只要安装好node和npm，接下来我们就可以进行Fabric Node SDK Application的开发了。由于我们想基于官方Example的e2e_cli里面的Fabric网络来写程序，关于Fabric网络的搭建我就不多说，大家可以参考我之前的博客。总之结果就是我们现在已经成功运行了e2e_cli这个网络，也就是说Example02这个ChainCode已经安装部署，并且测试通过了，我们接下来只是换用Node SDK的方式进行查询和调用。2.编写package.json并下载依赖模块
我们首先在当前用户的根目录建立一个nodeTest的文件夹，用于存放我们关于node的相关项目文件，然后在其中新建一个包配置文件，package.json
mkdir ~/nodeTest
cd ~/nodeTest
vi package.json
在这个文件中，我们可以定义很多项目相关的属性，这篇博客详细的介绍了每个属性有什么用，大家可以参考：http://www.cnblogs.com/tzyy/p/5193811.html
总之，最后我们在package.json中放入了以下内容：
{
"name": "nodeTest",
"version": "1.0.0",
"description": "Hyperledger Fabric Node SDK Test Application",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"dependencies": {
"fabric-ca-client": "^1.0.0",
"fabric-client": "^1.0.0"
},
"author": "Devin Zeng",
"license": "Apache-2.0",
"keywords": [
"Hyperledger",
"Fabric",
"Test",
"Application"
]
}
最主要的就是dependencies，这里我们放了Fabric CA Client和Fabric Node SDK的Client，虽然本示例中没用到CA Client，但是以后会用到，所以先放在这里了。
编辑保存好该文件后，我们就可以运行npm install命令来下载所有相关的依赖模块，但是由于npm服务器在国外，所以下载可能会很慢，感谢淘宝为我们提供了国内的npm镜像，使得安装npm模块快很多。运行的命令是：npm install --registry=https://registry.npm.taobao.org
运行完毕后我们查看一下nodeTest目录，可以看到多了一个node_modules文件夹。这里就是使用刚才的命令下载下来的所有依赖包。
2.编写对Fabric的Query方法
下面我们新建一个query.js文件，开始我们的Fabric Node SDK编码工作。由于代码比较长，所以我就不分步讲了，直接在代码中增加注释，将完整代码贴出来：
'use strict';
var hfc = require('fabric-client');
var path = require('path');
var sdkUtils = require('fabric-client/lib/utils')
var fs = require('fs');
var options = {
user_id: 'Admin@org1.example.com',
msp_id:'Org1MSP',
channel_id: 'mychannel',
chaincode_id: 'mycc',
network_url: 'grpcs://localhost:7051',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc
privateKeyFolder:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/keystore',
signedCert:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/signcerts/Admin@org1.example.com-cert.pem',
tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt',
server_hostname: "peer0.org1.example.com"
};
var channel = {};
var client = null;
const getKeyFilesInDir = (dir) => {
//该函数用于找到keystore目录下的私钥文件的路径
var files = fs.readdirSync(dir)
var keyFiles = []
files.forEach((file_name) => {
let filePath = path.join(dir, file_name)
if (file_name.endsWith('_sk')) {
keyFiles.push(filePath)
}
})
return keyFiles
}
Promise.resolve().then(() => {
console.log("Load privateKey and signedCert");
client = new hfc();
var createUserOpt = {
username: options.user_id,
mspid: options.msp_id,
cryptoContent: { privateKey: getKeyFilesInDir(options.privateKeyFolder)[0],
signedCert: options.signedCert }
}
//以上代码指定了当前用户的私钥，证书等基本信息
return sdkUtils.newKeyValueStore({
path: "/tmp/fabric-client-stateStore/"
}).then((store) => {
client.setStateStore(store)
return client.createUser(createUserOpt)
})
}).then((user) => {
channel = client.newChannel(options.channel_id);
let data = fs.readFileSync(options.tls_cacerts);
let peer = client.newPeer(options.network_url,
{
pem: Buffer.from(data).toString(),
'ssl-target-name-override': options.server_hostname
}
);
peer.setName("peer0");
//因为启用了TLS，所以上面的代码就是指定TLS的CA证书
channel.addPeer(peer);
return;
}).then(() => {
console.log("Make query");
var transaction_id = client.newTransactionID();
console.log("Assigning transaction_id: ", transaction_id._transaction_id);
//构造查询request参数
const request = {
chaincodeId: options.chaincode_id,
txId: transaction_id,
fcn: 'query',
args: ['a']
};
return channel.queryByChaincode(request);
}).then((query_responses) => {
console.log("returned from query");
if (!query_responses.length) {
console.log("No payloads were returned from query");
} else {
console.log("Query result count = ", query_responses.length)
}
if (query_responses[0] instanceof Error) {
console.error("error from query = ", query_responses[0]);
}
console.log("Response is ", query_responses[0].toString());//打印返回的结果
}).catch((err) => {
console.error("Caught Error", err);
});
编写完代码，我们想要测试一下我们的代码是否靠谱，直接运行
node query.js
即可，我们可以看到，a账户的余额是90元。
studyzy@ubuntu1:~/nodeTest$ node query.js
Load privateKey and signedCert
Make query
Assigning transaction_id: ee3ac35d40d8510813546a2216ad9c0d91213b8e1bba9b7fe19cfeff3014e38a
returned from query
Query result count = 1
Response is 90
为什么a账户是90？因为我们跑e2e_cli的Fabric网络时，系统会自动安装Example02的ChainCode，然后自动跑查询，转账等操作。
3.编写对Fabric的Invoke方法
相比较于Query方法，Invoke方法要复杂的多，主要是因为Invoke需要和Orderer通信，而且发起了Transaction之后，还要设置EventHub来接收消息。下面贴出invoke.js的全部内容，对于比较重要的部分我进行了注释:
'use strict';
var hfc = require('fabric-client');
var path = require('path');
var util = require('util');
var sdkUtils = require('fabric-client/lib/utils')
const fs = require('fs');
var options = {
user_id: 'Admin@org1.example.com',
msp_id:'Org1MSP',
channel_id: 'mychannel',
chaincode_id: 'mycc',
peer_url: 'grpcs://localhost:7051',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc
event_url: 'grpcs://localhost:7053',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc
orderer_url: 'grpcs://localhost:7050',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc
privateKeyFolder:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/keystore',
signedCert:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/signcerts/Admin@org1.example.com-cert.pem',
peer_tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt',
orderer_tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/ordererOrganizations/example.com/orderers/orderer.example.com/tls/ca.crt',
server_hostname: "peer0.org1.example.com"
};
var channel = {};
var client = null;
var targets = [];
var tx_id = null;
const getKeyFilesInDir = (dir) => {
//该函数用于找到keystore目录下的私钥文件的路径
const files = fs.readdirSync(dir)
const keyFiles = []
files.forEach((file_name) => {
let filePath = path.join(dir, file_name)
if (file_name.endsWith('_sk')) {
keyFiles.push(filePath)
}
})
return keyFiles
}
Promise.resolve().then(() => {
console.log("Load privateKey and signedCert");
client = new hfc();
var createUserOpt = {
username: options.user_id,
mspid: options.msp_id,
cryptoContent: { privateKey: getKeyFilesInDir(options.privateKeyFolder)[0],
signedCert: options.signedCert }
}
//以上代码指定了当前用户的私钥，证书等基本信息
return sdkUtils.newKeyValueStore({
path: "/tmp/fabric-client-stateStore/"
}).then((store) => {
client.setStateStore(store)
return client.createUser(createUserOpt)
})
}).then((user) => {
channel = client.newChannel(options.channel_id);
let data = fs.readFileSync(options.peer_tls_cacerts);
let peer = client.newPeer(options.peer_url,
{
pem: Buffer.from(data).toString(),
'ssl-target-name-override': options.server_hostname
}
);
//因为启用了TLS，所以上面的代码就是指定Peer的TLS的CA证书
channel.addPeer(peer);
//接下来连接Orderer的时候也启用了TLS，也是同样的处理方法
let odata = fs.readFileSync(options.orderer_tls_cacerts);
let caroots = Buffer.from(odata).toString();
var orderer = client.newOrderer(options.orderer_url, {
'pem': caroots,
'ssl-target-name-override': "orderer.example.com"
});
channel.addOrderer(orderer);
targets.push(peer);
return;
}).then(() => {
tx_id = client.newTransactionID();
console.log("Assigning transaction_id: ", tx_id._transaction_id);
//发起转账行为，将a->b 10元
var request = {
targets: targets,
chaincodeId: options.chaincode_id,
fcn: 'invoke',
args: ['a', 'b', '10'],
chainId: options.channel_id,
txId: tx_id
};
return channel.sendTransactionProposal(request);
}).then((results) => {
var proposalResponses = results[0];
var proposal = results[1];
var header = results[2];
let isProposalGood = false;
if (proposalResponses && proposalResponses[0].response &&
proposalResponses[0].response.status === 200) {
isProposalGood = true;
console.log('transaction proposal was good');
} else {
console.error('transaction proposal was bad');
}
if (isProposalGood) {
console.log(util.format(
'Successfully sent Proposal and received ProposalResponse: Status - %s, message - "%s", metadata - "%s", endorsement signature: %s',
proposalResponses[0].response.status, proposalResponses[0].response.message,
proposalResponses[0].response.payload, proposalResponses[0].endorsement.signature));
var request = {
proposalResponses: proposalResponses,
proposal: proposal,
header: header
};
// set the transaction listener and set a timeout of 30sec
// if the transaction did not get committed within the timeout period,
// fail the test
var transactionID = tx_id.getTransactionID();
var eventPromises = [];
let eh = client.newEventHub();
//接下来设置EventHub，用于监听Transaction是否成功写入，这里也是启用了TLS
let data = fs.readFileSync(options.peer_tls_cacerts);
let grpcOpts = {
pem: Buffer.from(data).toString(),
'ssl-target-name-override': options.server_hostname
}
eh.setPeerAddr(options.event_url,grpcOpts);
eh.connect();
let txPromise = new Promise((resolve, reject) => {
let handle = setTimeout(() => {
eh.disconnect();
reject();
}, 30000);
//向EventHub注册事件的处理办法
eh.registerTxEvent(transactionID, (tx, code) => {
clearTimeout(handle);
eh.unregisterTxEvent(transactionID);
eh.disconnect();
if (code !== 'VALID') {
console.error(
'The transaction was invalid, code = ' + code);
reject();
} else {
console.log(
'The transaction has been committed on peer ' +
eh._ep._endpoint.addr);
resolve();
}
});
});
eventPromises.push(txPromise);
var sendPromise = channel.sendTransaction(request);
return Promise.all([sendPromise].concat(eventPromises)).then((results) => {
console.log(' event promise all complete and testing complete');
return results[0]; // the first returned value is from the 'sendPromise' which is from the 'sendTransaction()' call
}).catch((err) => {
console.error(
'Failed to send transaction and get notifications within the timeout period.'
);
return 'Failed to send transaction and get notifications within the timeout period.';
});
} else {
console.error(
'Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...'
);
return 'Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...';
}
}, (err) => {
console.error('Failed to send proposal due to error: ' + err.stack ? err.stack :
err);
return 'Failed to send proposal due to error: ' + err.stack ? err.stack :
err;
}).then((response) => {
if (response.status === 'SUCCESS') {
console.log('Successfully sent transaction to the orderer.');
return tx_id.getTransactionID();
} else {
console.error('Failed to order the transaction. Error code: ' + response.status);
return 'Failed to order the transaction. Error code: ' + response.status;
}
}, (err) => {
console.error('Failed to send transaction due to error: ' + err.stack ? err
.stack : err);
return 'Failed to send transaction due to error: ' + err.stack ? err.stack :
err;
});
保存文件并退出，接下来测试一下我们的代码，运行：
node invoke.js
我们可以看到系统返回如下结果：
Load privateKey and signedCert
Assigning transaction_id: 1adbf20ace0d1601b00cc2b9dfdd4a431cfff9a13f6a6f5e5e4a80c897e0f7a8
transaction proposal was good
Successfully sent Proposal and received ProposalResponse: Status - 200, message - "OK", metadata - "", endorsement signature: 0D x��N��n�#���/�G���QD�w�����As� \]��FfWҡ�+������=m9I���� 6�i
info: [EventHub.js]: _connect - options {"grpc.ssl_target_name_override":"peer0.org1.example.com","grpc.default_authority":"peer0.org1.example.com"}
The transaction has been committed on peer localhost:7053
event promise all complete and testing complete
Successfully sent transaction to the orderer.
从打印出的结果看，我们的转账已经成功了，我们可以重新调用之前写的query.js重新查询，可以看到a账户的余额已经变少了10元。
4.总结
我们以上的query和Invoke都是参照了官方的fabcar示例，该示例在https://github.com/hyperledger/fabric-samples/tree/release/fabcar
这只是简单的测试Node SDK是否可用，如果我们要做项目，那么就会复杂很多，可以参考官方的两个项目：
https://github.com/hyperledger/fabric-samples/tree/release/balance-transfer
https://github.com/IBM-Blockchain/marbles
我之前一直卡在怎么基于某个用户的私钥和证书来设置当前的Context，后来感谢neswater的帮助，终于才解决了这个问题。还有就是TLS的问题，官方给出的fabcar是没有TLS的，我搞了半天才搞定，原来除了制定TLS证书之外，我们访问Peer的URL也是不一样的。
最后，大家如果想进一步探讨Fabric或者使用中遇到什么问题可以加入QQ群【494085548】大家一起讨论。