Apache Dubbo async processor

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Introduction

We plan to include two parts in this repo

  • AsyncSignal, specially designed to distinguish async method.
  • A compiler hacker processer that is able to generate async counterpart for each method in you Dubbo service interface.

AsyncSignal

AsyncSignal is an optional convenient type provided to unify your service definitions when you need an extra async method signature.

Imagine you have a Dubbo service defined like this:

public interface GreetingsService {
    String sayHi(String name);
}

Overwrite this method with a new one.

public interface GreetingsService {
    String sayHi(String name);
    
    // AsyncSignal is totally optional, you can use any parameter type as long as java allows your to do that.
    default CompletableFuture<String> sayHi(String name, AsyncSignal signal) {
        return CompletableFuture.completedFuture(sayHi(name));
    }
}

Now, you can call the new method with the CompletableFuture signature directly on Consumer side.

Compiler hacker processer

It should run at compile time, and overwrite each method in your service definition with an async equivalence. I think we can try to realize it by referencing lombok.

Conclude

The essential part is to overwrite a new async method. Another way would be to generate a new method with a different name, for example, sayHiAsync, then we can get rid of AsyncSignal. But there's an obvious flaw of this approach, that is, all method level configurators and routers defined to sayHi will not take effect anymore.

public interface GreetingsService {
    String sayHi(String name);
    
    // Any name is ok
    default CompletableFuture<String> sayHiAsync(String name) {
        return CompletableFuture.completedFuture(sayHi(name));
    }
}