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.

Building Locally

You will need to install

• asdf

  • Install the Rust plugin
  • Install the Java plugin
    • Make sure to follow instructions in the MacOS section.
  • Then, run asdf install at the root of the repo.

  If you prefer to not use asdf, you can install Rust directly and install Java via sdkman. Reference .tool-versions to ensure you are installing the correct versions.

• Docker

build