Generate Server. Missing types

In API clasess should be sometithg like this:
default Optional getObjectMapper() {
return Optional.empty();
}

default Optional<HttpServletRequest> getRequest() {
    return Optional.empty();
}

default Optional<String> getAcceptHeader() {
    return getRequest().map(r -> r.getHeader("Accept"));
}

Swagger-codegen version

2.4.14-SNAPSHOT

Swagger declaration file content or url

The issue does not name a template, source file, test, or Swagger declaration. Reproduce generation with Swagger-codegen 2.4.14-SNAPSHOT, then trace the generated API classes to find where the ObjectMapper, HttpServletRequest, and Accept-header methods should receive their types. Done means generated API classes contain the expected typed methods.