The Slug RPC Client is a little framework for talking to (some) JSON-RPC over HTTP services.

Defining a Service Interface

To begin, define an interface representing the service. Each method on the interface should accept zero or one arguments and return zero or one results. Parameters and results SHOULD be simple POJOs (allow me to suggest the slug-maven-plugin), although technically anything that Jackson can figure out will work.

public interface MySweetService {

    /**
     * Does some sweet stuff.
     */
    DoSweetStuffResult doSweetStuff(DoSweetStuffRequest request);
}

Creating a Client

Next use the RpcClientBuilder to create an instance of your interface hooked up to a particular endpoint.

String uri = "https://my.sweet.service/my/sweet/service";
MySweetService service = new RpcClientBuilder(MySweetService.class, uri)
        // Other optional configuration here.
        .build();

Calling methods on the returned service object will issue HTTP POST requests to the provided endpoint with a JSON-RPC 2.0 request object in the payload and attempt to parse a JSON-RPC 2.0 response object from the response payload.

Some Details

• The name of the interface method is taken to be the name of the remote procedure to call. I might look into an annotation to override that, but keeping it simple for now.
• Only one argument is allowed, which is serialized to a JSON object and sent in the params field of the request. No support for positional parameters is planned.
• There is currently no support for notifications; void interface methods will always wait for a response. I could be convinced, but it's not a high priority.
• Ids are generated randomly on requests, but ignored on response since HTTP provides its own (albeit inferior) mechanisms for request/response correlation.
• No support for batch requests yet. Potentially interesting in the future maybe?