Change the insertion order of `ExceptionHandlerFunction`

Let’s look at the following example:

 1: ServerBuilder sb = ...
 2: sb.annotatedService()
 3:   .decorator(delegate -> (ctx, req) -> {
 4:       return delegate.serve(ctx, req).mapHeaders(headers -> {
 5:           System.err.println("This isn't called.");
 6:           return headers;
 7:       });
 8:   })
 9:   .exceptionHandlers((ctx, req, cause) -> HttpResponse.of(200))
10:   .build(new Object() {
11:      @Get("/foo")
12:      public HttpResponse foo(String foo) {
13:          throw new IllegalArgumentException();
14:      }
15:  });

The fifth line is not called because the specified exception handler is attached before the decorator so mapHeaders is not applied:

A request flow:
request -> ExceptionHandlerFunction -> decorator -> Request(Response)Converter -> Annotated service

The reason why the ExceptionHandlerFunction is located before the decorator is that we wanted to catch the exception raised in the decorator. However, it has this bypassing problem, and also ExceptionHandlerFunction is not installed with the Request(Response)Converter at the same level which users expect so.

[minwoox]

Thanks for your opinion. 😄

I was just worried that this can be a breaking change.

Yeah, it could be a breaking change so we might be able to change that in 2.0 Or, we can fix it right now if everyone thinks that it’s a bug. 😆

[ks-yim]

Agree with the direction. I was quite confused with the differentiation between ServerErrorHandler and ExceptionHandlerFunction in the past and the change will make their roles more clear.

I was just worried that this can be a breaking change. cc. @ghkim3221