Add RequestContextResolver Feature

[SentryMan]

Adds a RequestContextResolver interface that lets you retrieve a javalin/helidon request object wherever it is wired. Useful for AOP and the like.

The default implementation uses ThreadLocal like a poor man's version of the upcoming ScopedValue. Since SV are in preview, we cannot add an implementation using them directly, so users will have to provide their own implementation of RequestContextResolver using SVs.

when enabled, the controller will generate like this.

@Generated("avaje-javalin-generator")
@Component
public class TestController2$Route implements WebRoutes {

  private final TestController2 controller;
  private final RequestContextResolver resolver;
  private final JsonType<String> stringJsonType;

  public TestController2$Route(
      TestController2 controller, Jsonb jsonb, RequestContextResolver resolver) {
    this.controller = controller;
    this.resolver = resolver;
    this.stringJsonType = jsonb.type(String.class);
  }

  @Override
  public void registerRoutes() {

    ApiBuilder.post("/test/strBody", ctx -> {
      ctx.status(201);
      var body = ctx.body();
      //for the execution of the supplier, the context is bound to the thread, and can be retrieved by the resolver class implementation.
      var result = resolver.supplyWith(new ServerContext(ctx,ctx), () -> controller.strBody(body));
      stringJsonType.toJson(result, ctx.contentType("application/json").outputStream());
    });
  }

}

• adds ServerContext class for getting server request and response
• adds RequestContextResolver interface for instrumenting server context inside a controller request
• adds a default thread-local implementation of RequestContextResolver
• adds an inject plugin to add a default resolver for inject applications
• adds new property to HTTP annotations to enable request context instrumentation
• modifies generators to instrument request context when enabled

Big thanks to @LoonyRules for helping me figure out how to implement this.

[rob-bygrave]

How does this API work for servers that use request + response rather than the single context parameter? resolver.supplyWith(ctx, ... is oriented to servers like Javalin that have a single context parameter.

[SentryMan]

Hmm, so it is

[SentryMan]

I'll modify the API to handle it

[SentryMan]

I added a ServerContext class so that both can be retrieved

[SentryMan]

I'm good with most of this, but not sure about adding the inject plugin given that whole module issue. Do you think I should keep or remove it?

[rob-bygrave]

Lets keep it and see how things evolve over the next week.