Spring WebClient map error to response in HEAD request

Question

I want to handle a HEAD endpoint so that if the HTTP status is successful, I return true. If it's 404, I return false. Else, I want to throw different exceptions.

I currently have the following:

    boolean head(String param) {
        return webClient.head()
            .uri(fromPath(PATH).pathSegment(param))
            .exchangeToMono(response -> {
                if(response.statusCode().is2xxSuccessful()){
                    return Mono.just(Boolean.TRUE);
                } else if (response.statusCode().equals(NOT_FOUND)){
                    return Mono.just(Boolean.FALSE);
                }
                //what to do here?
            })
            .onErrorMap(this::mapErrorFunction)
            .block();
    }

My mapErrorFunction is already in use by other methods, and it's the one I want to use since depending on the raised exception, one thing or another will be done. However, it requires a parameter of type Throwable which I don't have when reaching the end of the exchangeToMono block, to I can't do this.mapErrorFunction at that point.

For the record, the successful and the 404 cases are properly working.

How can I do this? Maybe exchangeToMono is not the right option here.

Answer 1

The answer is to throw the exception after the if else and let the onErrorMap method handle it:

   boolean head(String param) {
        return Boolean.TRUE.equals(webClient.head()
        .uri(uri.toUriString())
        .exchangeToMono(response -> {
            if (response.statusCode().is2xxSuccessful()) {
                return Mono.just(Boolean.TRUE);
            } else if (response.statusCode().equals(NOT_FOUND)) {
                return Mono.just(Boolean.FALSE);
            }
            return response.createException().flatMap(Mono::error);

        })
        .onErrorMap(this::mapErrorFunction)
        .block());