Sunday 14 November 2021

An Exception wrapper suitable for a RESTful API

User Story

As a third line support engineer

I want to be able to go to the server class that throws an exception reported by a client

So that I do not need to look for the stack trace in the server logs


Client code

if (responseCode != 200) {
    throw new TaskException(
        "Error occurred while processing the scan response: " + 
        "response code: " + responseCode + 
        " response body: " + responseContent.getResponseBody());

Server code

  if (null != header && header.startsWith(BEARER)) {
        String token = header.substring(BEARER.length()).trim();
        try {
            final Jws jws = Jwts.parser().setSigningKeyResolver(jwtPublicKeyResolver)
        } catch (JwtException ex) {
            String errorMessage = "Invalid JWT token. ";
            setError(httpServletResponse, errorMessage + ex.getMessage());

This results in the following being reported by the second level support agent monitoring the client logs:

[Error occurred while processing the scan response : response code: 401 response body: Invalid JWT token. Error accessing publickey Api]:

What we, as Third Line Support, want is to know which server class throws the exception, ideally without grepping the code base or opening the server logs.

A better Exception message would be:

[Problem with scan response: status code: 401, body: com.corp.server.validation.JwtValidator.validate() line 72: JWT token Exception: Error accessing Public Key API]

This is the motivation for the StackAwareException, a wrapper exception which adds the class, method and line number of the first element of the wrapped exception's stack trace.