Custom Not Found Handler

By default, Zuplo will return a 404 (using problem details) if no matching path/method combination is found. You can override this behavior by adding code to the zuplo.runtime.ts file (see runtime extensions).

For example - a custom not found handler can be used to return a 405 - Method Not Allowed if a matching path is found, but no matching METHOD, here is an example function that would implement this behavior:

export function runtimeInit(runtime: RuntimeExtensions) {
    //add a custom not found handler
    runtime.notFoundHandler = async (request, context, notFoundOptions) => {
    if (notFoundOptions.routesMatchedByPathOnly.length > 0) {
      // It is required to have an 'Allow' header with a 405 response
      // Generate a string of allowed methods
      const allowedMethods = notFoundOptions.routesMatchedByPathOnly
        .map((route) => route.methods)
        .reduce((acc, val) => acc.concat(val), [])
        .join(", ");
 
      return HttpProblems.methodNotAllowed(
        request,
        context,
        {},
        { allow: allowedMethods }
      );
    }
 
    return HttpProblems.notFound(request, context);
  };

An error in your zuplo.runtime.ts can break your gateway for all requests. Be sure to carefully review any custom code in this file and add generous error handling where appropriate.

Was this article helpful?