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).
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();
}
}
| Package | Description |
|---|---|
| org.hyperledger.fabric.gateway |
This package provides the set of interfaces that enable a Java application to
interact with a Fabric blockchain network.
|
| org.hyperledger.fabric.gateway.spi |
This package provides the set of interfaces that enable a Java developer to
extend the set of built in handlers for controlling gateway strategies.
|