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.
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).
package org.example;
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;
public final 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 = Wallet.createFileSystemWallet(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.submitTransaction("createCar", "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 e) {
e.printStackTrace();
}
}
}Full Javadoc documentation of the SDK is published here.
Depend on development snapshots with the following pom.xml entries:
<repositories>
<repository>
<id>hyperledger-snapshots-repo</id>
<url>https://nexus.hyperledger.org/content/repositories/snapshots</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>org.hyperledger.fabric-gateway-java</groupId>
<artifactId>fabric-gateway-java</artifactId>
<version>1.4.0-SNAPSHOT</version>
</dependency>
</dependencies>Depend on development snapshots with the following build.gradle entries:
repositories {
maven {
url 'https://nexus.hyperledger.org/content/repositories/snapshots/'
}
}
dependencies {
implementation 'org.hyperledger.fabric-gateway-java:fabric-gateway-java:1.4.0-SNAPSHOT'
}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. For the tests to locate the peer, orderer and certificate authority
containers running locally, the following entries are required in the local hosts file:
127.0.0.1 ca0.example.com
127.0.0.1 ca1.example.com
127.0.0.1 orderer.example.com
127.0.0.1 peer0.org1.example.com
127.0.0.1 peer0.org2.example.com
All classes and methods have a high coverage (~90%) of unit tests. These are written using the JUnit, AssertJ and Mockito frameworks.
Scenario tests are written using the Cucumber BDD framework.