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About

This project provides written in Java API for interaction with a Polkadot or Substrate based network.

Key features

  • Java 8 or higher.

The main idea is to make this library available and usable for as many projects as possible.

  • Non-blocking API.

The API is designed to be non-blocking in order to not engage resources for waiting responses from a node, especially when working with web sockets. Each method returns CompletableFuture<>.

  • Declarative approach.

Some of our goals are:

  • make API simpler for usage;
  • let users organize their code similar to the one in the pallet they are interacting with;
  • hide difficulties of low level and infrastructure code;
  • facilitate the future maintenance.

The best approach to reach project’s goals is to use annotations and code generation techniques. Below are listed some annotations that this API shall provide:

  • Scale

    • @ScaleWriter;
    • @ScaleReader;
    • @Scale;
    • @ScaleGeneric;
    • @Ignore;

  • Rpc

    • @RpcInterface;
    • @RpcCall;
    • @RpcSubscription;
    • @RpcEncoder;
    • @RpcDecoder;

  • Pallet

    • @Pallet;
    • @Transaction;
    • @Storage;
    • @Event.

These allow the generation of scale serializers, deserializers, RPC methods, code for interaction with pallet, etc. More examples you can find below.

  • Deferred parametrization of codecs

Annotations for codecs allow deferring parameters of a generic until it's used at an RPC method. E.g.:

@RequiredArgsConstructor
@Getter
@ScaleWriter
public class Some<A> {
   private final int number;
   private final A some;
}

@RpcInterface(section = "test")
public interface TestSection {
 @RpcCall(method = "sendSome")
 CompletableFuture<Boolean> doNothing(@Scale Some<Parameter> value);
}

Annotation processors will generate scale writer for the class Some which expects another writer as a dependency. When a processor faces a parameter like Some<String> value, it injects the Strings's writer into the writer of Some.

  • GC Manageable requests.

We take care of either lost responses or canceled futures by not holding handlers that are needed to match an RPC request with a response.

  • Tests run with substrate node.

All API methods related to the substrate node will be tested for operability and compatibility. Currently, we use test containers and docker image parity/substrate:v3.0.0.