这篇文章主要介绍Hyperledger Fabric中Chaincode的Invoke功能怎么用，文中介绍的非常详细，具有一定的参考价值，感兴趣的小伙伴们一定要看完！
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Chaincode的Invoke 功能， 主要包括create, update, delete功能。
完整的实例代码如下：
'use strict';
/*
* Chaincode Invoke
*/
var Fabric_Client = require('fabric-client');
var path = require('path');
var util = require('util');
var os = require('os');
//
var fabric_client = new Fabric_Client();
// setup the fabric network
var channel = fabric_client.newChannel('mychannel');
var peer = fabric_client.newPeer('grpc://localhost:7051');
channel.addPeer(peer);
var order = fabric_client.newOrderer('grpc://localhost:7050')
channel.addOrderer(order);
//
var member_user = null;
var store_path = path.join(__dirname, 'hfc-key-store');
console.log('Store path:'+store_path);
var tx_id = null;
// create the key value store as defined in the fabric-client/config/default.json 'key-value-store' setting
Fabric_Client.newDefaultKeyValueStore({ path: store_path
}).then((state_store) => {
// assign the store to the fabric client
fabric_client.setStateStore(state_store);
var crypto_suite = Fabric_Client.newCryptoSuite();
// use the same location for the state store (where the users' certificate are kept)
// and the crypto store (where the users' keys are kept)
var crypto_store = Fabric_Client.newCryptoKeyStore({path: store_path});
crypto_suite.setCryptoKeyStore(crypto_store);
fabric_client.setCryptoSuite(crypto_suite);
// get the enrolled user from persistence, this user will sign all requests
return fabric_client.getUserContext('user1', true);
}).then((user_from_store) => {
if (user_from_store && user_from_store.isEnrolled()) {
console.log('Successfully loaded user1 from persistence');
member_user = user_from_store;
} else {
throw new Error('Failed to get user1.... run registerUser.js');
}
// get a transaction id object based on the current user assigned to fabric client
tx_id = fabric_client.newTransactionID();
console.log("Assigning transaction_id: ", tx_id._transaction_id);
// createCar chaincode function - requires 5 args, ex: args: ['CAR12', 'Honda', 'Accord', 'Black', 'Tom'],
// changeCarOwner chaincode function - requires 2 args , ex: args: ['CAR10', 'Dave'],
// must send the proposal to endorsing peers
var request = {
//targets: let default to the peer assigned to the client
chaincodeId: 'fabcar',
fcn: '',
args: [''],
chainId: 'mychannel',
txId: tx_id
};
// send the transaction proposal to the peers
return channel.sendTransactionProposal(request);
}).then((results) => {
var proposalResponses = results[0];
var proposal = results[1];
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"',
proposalResponses[0].response.status, proposalResponses[0].response.message));
// build up the request for the orderer to have the transaction committed
var request = {
proposalResponses: proposalResponses,
proposal: proposal
};
// set the transaction listener and set a timeout of 30 sec
// if the transaction did not get committed within the timeout period,
// report a TIMEOUT status
var transaction_id_string = tx_id.getTransactionID(); //Get the transaction ID string to be used by the event processing
var promises = [];
var sendPromise = channel.sendTransaction(request);
promises.push(sendPromise); //we want the send transaction first, so that we know where to check status
// get an eventhub once the fabric client has a user assigned. The user
// is required bacause the event registration must be signed
let event_hub = fabric_client.newEventHub();
event_hub.setPeerAddr('grpc://localhost:7053');
// using resolve the promise so that result status may be processed
// under the then clause rather than having the catch clause process
// the status
let txPromise = new Promise((resolve, reject) => {
let handle = setTimeout(() => {
event_hub.disconnect();
resolve({event_status : 'TIMEOUT'}); //we could use reject(new Error('Trnasaction did not complete within 30 seconds'));
}, 3000);
event_hub.connect();
event_hub.registerTxEvent(transaction_id_string, (tx, code) => {
// this is the callback for transaction event status
// first some clean up of event listener
clearTimeout(handle);
event_hub.unregisterTxEvent(transaction_id_string);
event_hub.disconnect();
// now let the application know what happened
var return_status = {event_status : code, tx_id : transaction_id_string};
if (code !== 'VALID') {
console.error('The transaction was invalid, code = ' + code);
resolve(return_status); // we could use reject(new Error('Problem with the tranaction, event status ::'+code));
} else {
console.log('The transaction has been committed on peer ' + event_hub._ep._endpoint.addr);
resolve(return_status);
}
}, (err) => {
//this is the callback if something goes wrong with the event registration or processing
reject(new Error('There was a problem with the eventhub ::'+err));
});
});
promises.push(txPromise);
return Promise.all(promises);
} else {
console.error('Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...');
throw new Error('Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...');
}
}).then((results) => {
console.log('Send transaction promise and event listener promise have completed');
// check the results in the order the promises were added to the promise all list
if (results && results[0] && results[0].status === 'SUCCESS') {
console.log('Successfully sent transaction to the orderer.');
} else {
console.error('Failed to order the transaction. Error code: ' + results[0].status);
}
if(results && results[1] && results[1].event_status === 'VALID') {
console.log('Successfully committed the change to the ledger by the peer');
} else {
console.log('Transaction failed to be committed to the ledger due to ::'+results[1].event_status);
}
}).catch((err) => {
console.error('Failed to invoke successfully :: ' + err);
});这段代码主要功能有两个， 一个是提交交易， 一个是获取交易结果。 关于Hyperledger Fabric 的交易流程的介绍在这里， 主要包括6个步骤。
其实， 对于客户端来说， 交易过程需要干两件事：
1 向背书节点发送交易提案
2 获取背书节点对交易提案的反馈， 并组装交易， 向orderer节点发送交易
而对于交易结果的获取， Hyperledger Fabric 是通过事件机制实现的。
通过fabric_client生成一个EventHub对象， 然后通过event_hub对象注册事件获取， 详细介绍见 Hyperledger Fabric SDK for node.js Class: EventHub 。
从文档可以看出， EventHub可以注册的事件有：
registerBlockEvent(onEvent, onError) 区块事件
registerChaincodeEvent(ccid, eventname, onEvent, onError) 链码事件
registerTxEvent(txid, onEvent, onError) 交易事件
首先看交易过程。交易包括发送提案和发送交易两个过程。交易过程主要封装请求链码的参数， 发送请求到背书节点， 代码如下：
// get a transaction id object based on the current user assigned to fabric client
tx_id = fabric_client.newTransactionID();
console.log("Assigning transaction_id: ", tx_id._transaction_id);
// createCar chaincode function - requires 5 args, ex: args: ['CAR12', 'Honda', 'Accord', 'Black', 'Tom'],
// changeCarOwner chaincode function - requires 2 args , ex: args: ['CAR10', 'Dave'],
// must send the proposal to endorsing peers
var request = {
//targets: let default to the peer assigned to the client
chaincodeId: 'fabcar',
fcn: 'createCar',
args: ['CAR100', 'Honda', 'Accord', 'Black', 'Jarvis'],
chainId: 'mychannel',
txId: tx_id
};
// send the transaction proposal to the peers
return channel.sendTransactionProposal(request);首先， 获取一个和当前用户关联的transaction id 对象， 该对象的定义在这里 。该方法 可以传入一个参数 boolean,默认为false， 如果为true, 则根据admin 用户的证书生成tansaction id 对象。
接下来构造sendTransactionProposal参数， 也就是提案的请求对象， 参数对象的定义在这里 。 这里需要注意的是chaincodeId, chainId, txId 是必须， 用来指定已经安装（intall）并且实例化(initantiate)的chaincode。 fcn 对应链码中定义的业务逻辑， 默认为invoke， args是fcn对应的参数， 所有的args格式都是一样的， 是一个string 数组。
参数构造完成， 就可以向背书节点发送交易提案了。执行成功的话， 返回提案结果对象， 实际上是https://fabric-sdk-node.github.io/global.html#ProposalResponseObject 对象。
接下来， 提交交易到orderer节点。
var proposalResponses = results[0];
var proposal = results[1];
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"',
proposalResponses[0].response.status, proposalResponses[0].response.message));
// build up the request for the orderer to have the transaction committed
var request = {
proposalResponses: proposalResponses,
proposal: proposal
};
// set the transaction listener and set a timeout of 30 sec
// if the transaction did not get committed within the timeout period,
// report a TIMEOUT status
var transaction_id_string = tx_id.getTransactionID(); //Get the transaction ID string to be used by the event processing
var promises = [];
var sendPromise = channel.sendTransaction(request);首先判断提案交易是不是成功
if (proposalResponses && proposalResponses[0].response &&
proposalResponses[0].response.status === 200) {如果成功， 构建交易参数， 并提交交易。参数的定义见： Hyperledger Fabric SDK for node.js Global 。包括提案执行的结果。
获取交易结果是通过事件机制实现的， 需要用到交易的tansaction id .在代码中是通过EventHub对象实现的。
具体步骤包括：
1 创建 EventHub对象
let event_hub = fabric_client.newEventHub();
event_hub.setPeerAddr('grpc://localhost:7053');2 获取一个事件源的连接
event_hub.connect();
3 注册并监听事件
Fabric提供的事件对象有：registerBlockEvent, registerTxEvent 和 registerChaincodeEvent . 这里只关注registerTxEvent事件。
event_hub.registerTxEvent(transaction_id_string, (tx, code) => {
//......详细文档查看 Hyperledger Fabric SDK for node.js Class: EventHub 。第一个参数为 上文提到的transaction id 字符串， 第二个参数是一个回调函数， 有两个参数， 第一个是一个Transaction对象， 第二个是一个字符串， 表示交易是否valid状态的字符串。
4 断开连接
event_hub.disconnect();
以上是“Hyperledger Fabric中Chaincode的Invoke功能怎么用”这篇文章的所有内容，感谢各位的阅读！希望分享的内容对大家有帮助，更多相关知识，欢迎关注创新互联行业资讯频道！
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