Overview

The fabric-gateway package enables Node.js developers to build client applications using the Hyperledger Fabric programming model as described in the Running a Fabric Application tutorial of the Fabric documentation.

TypeScript definitions are included in this package.

Getting started

Client applications interact with the blockchain network using a Fabric Gateway. A session for a given client identity is established by calling connect() with a gRPC connection to a Fabric Gateway endpoint, client identity, and client signing implementation. The returned Gateway enables interaction with any of the blockchain Networks (channels) accessible through the Fabric Gateway. This in turn provides access to Smart Contracts within chaincode deployed to that blockchain network, and to which transactions can be submitted or queries can be evaluated.

gRPC connections to a Fabric Gateway may be shared by all Gateway instances interacting with that Fabric Gateway.

Example

The following complete example shows how to connect to a Fabric network, submit a transaction and query the ledger state using an instantiated smart contract.

import * as grpc from '@grpc/grpc-js';
import { connect, hash, signers } from '@hyperledger/fabric-gateway';
import * as crypto from 'node:crypto';
import { promises as fs } from 'node:fs';
import { TextDecoder } from 'node:util';

const utf8Decoder = new TextDecoder();

async function main(): Promise<void> {
    const credentials = await fs.readFile('path/to/certificate.pem');

    const privateKeyPem = await fs.readFile('path/to/privateKey.pem');
    const privateKey = crypto.createPrivateKey(privateKeyPem);
    const signer = signers.newPrivateKeySigner(privateKey);

    const tlsRootCert = await fs.readFile('path/to/tlsRootCertificate.pem');
    const client = new grpc.Client('gateway.example.org:1337', grpc.credentials.createSsl(tlsRootCert));

    const gateway = connect({
        identity: { mspId: 'myorg', credentials },
        signer,
        hash: hash.sha256,
        client,
    });

    try {
        const network = gateway.getNetwork('channelName');
        const contract = network.getContract('chaincodeName');

        const putResult = await contract.submitTransaction('put', 'time', new Date().toISOString());
        console.log('Put result:', utf8Decoder.decode(putResult));

        const getResult = await contract.evaluateTransaction('get', 'time');
        console.log('Get result:', utf8Decoder.decode(getResult));
    } finally {
        gateway.close();
        client.close();
    }
}

main().catch(console.error);
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