Hyperledger Fabric中Chaincode的Invoke功能怎么用

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！

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 networkvar 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' settingFabric_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，欢迎关注行业资讯频道！