Minimum Spring Boot Code to log 404s

Question

In my Spring Boot Application, I'm currently leveraging the resources/public/error/404.html custom error page to show (automagically) this 404 page errors on invalid URLS.

Is there an easy way to retain this auto functionality, and add a simple log message (with the invalid URL) for every such 404 ?

Ideally with as little code as possible I would want some like :

//Some code
LOGGER.warn("Invalid URL " + request.url);
//Some more code

Answer 1

You need to define a custom ErrorViewResolver:

@Component
public class MyErrorViewResolver implements ErrorViewResolver {

    @Override
    public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status, Map<String, Object> model) {
    if (HttpStatus.NOT_FOUND == status) {
        LoggerFactory.getLogger(this.getClass()).error("error 404 for url " + model.get("path"));
        return new ModelAndView("error404", model);
    }
    else {
        return new ModelAndView("error", model);
    }
  }
}

This MyErrorViewResolver will be automatically called in the BasicErrorController class.

For a 404 error, the view "error404" will be displayed.

For the other errors, the view "error" will be displayed.

Views must be in the "templates" folder (resources/templates/error404.html).