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Designer to Gateway Communication (RPC)

When building a module with both Designer and Gateway components, it is often necessary to provide some sort of communication link between them. The project management system handles notifying the Gateway of resource changes, but for more dynamic communication, the RPC (remote procedure call) system is available.

The RPC system is easy to use, and works as follows:

  1. In the Designer, the module uses GatewayConnectionManager.getInstance().getGatewayInterface().moduleInvoke(...) to send an invocation call to the Gateway for the provided module ID, with the given function name and parameters.
  2. On the Gateway, the system looks up the module ID provided, and calls getRPCHandler on its module hook.
  3. The Gateway then reflectively locates the desired function, executes it, and returns the result.

Design Best Practice​

Instead of calling GatewayInterface.moduleInvoke() yourself, you can use the class ModuleRPCFactory in conjunction with an interface that you define to create a dynamic proxy automatically. Defining your functionality in an interface that is implemented by your RPC handler is a good idea in general, as you will have a single definition of what RPC functions are available.

This paradigm is demonstrated below, with a simple function that sends someone’s name from the Designer to the Gateway to retrieve a greeting for them.

The RPC Interface - in the Common Package​

public interface ModuleRPC {
    String getGreeting(String firstName);
}

The Gateway Implementation - in the Gateway Scope​

public class ModuleRPCImpl implements ModuleRPC {
    public String getGreeting(String firstName){
        return "Hello, " + firstName;
    }
}

In the GatewayModuleHook​

public Object getRPCHandler(ClientReqSession session, String projectId) {
    return new ModuleRPCImple();
}

Using the RPC Class - in the Client Scope​

ModuleRPC rpc = ModuleRPCFactory.create(ModuleMeta.MODULE_ID, ModuleRPC.class);
System.out.println(rpc.getGreeting("Bill"));