org.hyperledger.fabric.gateway

Interface Gateway

All Superinterfaces:

AutoCloseable

public interface Gateway
extends AutoCloseable

The Gateway provides the connection point for an application to access the Fabric network as a specific user. It is instantiated from a Builder instance that is created using createBuilder() and configured using a common connection profile and a Wallet identity. It can then be connected to a fabric network using the Gateway.Builder.connect() method. Once connected, it can then access individual Network instances (channels) using the getNetwork method which in turn can access the Contract installed on a network and submit transactions to the ledger.

Gateway instances should be reused for multiple transaction invocations and only closed once connection to the Fabric network is no longer required.

     Gateway.Builder builder = Gateway.createBuilder()
             .identity(wallet, "user1")
             .networkConfig(networkConfigFile);

     try (Gateway gateway = builder.connect()) {
         Network network = gateway.getNetwork("mychannel");
         // Interactions with the network
     }
 

Service discovery

Service discovery allows the client to dynamically discover nodes (peers and orderers) within a network that are not defined in the connection profile, and is enabled using Gateway.Builder.discovery(boolean). With service discovery enabled, the client will receive the public network address of each node. If these network addresses can be reached directly by the client, no additional configuration is required.

In some cases nodes cannot be accessed directly by the client on their public network address. For example, when nodes are hosted in Docker containers, and the client is running on the local machine outside of the Docker network. In this case service discovery will report the network address of nodes within the Docker network but the client will need to access nodes using the localhost address. Setting the following environment variable will force service discovery to report the localhost address for all nodes.

org.hyperledger.fabric.sdk.service_discovery.as_localhost=true

An alternative approach is to modify the local hosts file for the client machine to resolve the network address of nodes running in a Docker network to the localhost address.

Note that the port numbers of nodes obtained through service discovery remain unchanged so ports forwarded from the local machine's network must match the port numbers of nodes within the Docker network.

See Also:

Developing Fabric Applications - Gateway

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	Gateway.Builder The Gateway Builder interface defines the options that can be configured prior to connection.

Method Summary

Modifier and Type	Method and Description
void	close() Close the gateway connection and all associated resources, including removing listeners attached to networks and contracts created by the gateway.
static Gateway.Builder	createBuilder() Creates a gateway builder which is used to configure the gateway options prior to connecting to the Fabric network.
org.hyperledger.fabric.sdk.HFClient	getClient() Get the Client used by the gateway connection.
Identity	getIdentity() Get the identity associated with the gateway connection.
Network	getNetwork(String networkName) Returns an object representing a network.

Method Detail

getNetwork

Network getNetwork(String networkName)

Returns an object representing a network.

Parameters:

networkName - The name of the network (channel name)

Returns:

Network

Throws:

GatewayRuntimeException - if a configuration or infrastructure error causes a failure.

getIdentity

Identity getIdentity()

Get the identity associated with the gateway connection.

Returns:

The identity used by this Gateway.

createBuilder

static Gateway.Builder createBuilder()

Creates a gateway builder which is used to configure the gateway options prior to connecting to the Fabric network.

Returns:

A gateway connection.

getClient

org.hyperledger.fabric.sdk.HFClient getClient()

Get the Client used by the gateway connection.

Returns:

The Client used by this Gateway.

close

void close()

Close the gateway connection and all associated resources, including removing listeners attached to networks and contracts created by the gateway.

Specified by:

close in interface AutoCloseable