Hyperledger Fabric Gateway SDK for Java

The Fabric Gateway SDK allows applications to interact with a Fabric blockchain network. It provides a simple API to submit transactions to a ledger or query the contents of a ledger with minimal code.

The Gateway SDK implements the Fabric programming model as described in the Developing Applications chapter of the Fabric documentation.

How to use

The following shows a complete code sample of how to connect to a fabric network, submit a transaction and query the ledger state using an instantiated smart contract (fabcar sample).

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.concurrent.TimeoutException;

import org.hyperledger.fabric.gateway.Contract;
import org.hyperledger.fabric.gateway.ContractException;
import org.hyperledger.fabric.gateway.Gateway;
import org.hyperledger.fabric.gateway.Network;
import org.hyperledger.fabric.gateway.Wallet;
import org.hyperledger.fabric.gateway.Wallets;

class Sample {
    public static void main(String[] args) throws IOException {
        // Load an existing wallet holding identities used to access the network.
        Path walletDirectory = Paths.get("wallet");
        Wallet wallet = Wallets.newFileSystemWallet(walletDirectory);

        // Path to a common connection profile describing the network.
        Path networkConfigFile = Paths.get("connection.json");

        // Configure the gateway connection used to access the network.
        Gateway.Builder builder = Gateway.createBuilder()
                .identity(wallet, "user1")
                .networkConfig(networkConfigFile);

        // Create a gateway connection
        try (Gateway gateway = builder.connect()) {

            // Obtain a smart contract deployed on the network.
            Network network = gateway.getNetwork("mychannel");
            Contract contract = network.getContract("fabcar");

            // Submit transactions that store state to the ledger.
            byte[] createCarResult = contract.createTransaction("createCar")
                    .submit("CAR10", "VW", "Polo", "Grey", "Mary");
            System.out.println(new String(createCarResult, StandardCharsets.UTF_8));

            // Evaluate transactions that query state from the ledger.
            byte[] queryAllCarsResult = contract.evaluateTransaction("queryAllCars");
            System.out.println(new String(queryAllCarsResult, StandardCharsets.UTF_8));

        } catch (ContractException | TimeoutException | InterruptedException e) {
            e.printStackTrace();
        }
    }
}

API documentation

Full Javadoc documentation is published for each of the following versions:

• 2.0
• 1.4

Maven

Add the following dependency to your project's pom.xml file:

<dependency>
  <groupId>org.hyperledger.fabric</groupId>
  <artifactId>fabric-gateway-java</artifactId>
  <version>2.0.0</version>
</dependency>

Gradle

Add the following dependency to your project's build.gradle file:

implementation 'org.hyperledger.fabric:fabric-gateway-java:2.0.0'

Compatibility

The following table shows versions of Fabric, Java and other dependencies that are explicitly tested and that are supported for use with version 2.0 of the Fabric Gateway SDK. Refer to the appropriate GitHub branch for compatibility of other release versions.

	Tested	Supported
Fabric	2.0	2.0.x
Java	8	8+
Platform	Ubuntu 18.04

Building and testing

git clone https://github.com/hyperledger/fabric-gateway-java.git
cd fabric-gateway-java
mvn install

The mvn install command will download the dependencies and run all the unit tests and scenario tests. It will also generate all the crypto material required by these tests.

Docker is required to run the scenario tests.

Unit tests

All classes and methods have a high coverage (~90%) of unit tests. These are written using the JUnit, AssertJ and Mockito frameworks.

Scenario tests

Scenario tests are written using the Cucumber BDD framework.