protected Builder setRequest(ServletRequest request) {
            if (request != null) {
                ((WebSubjectContext) getSubjectContext()).setServletRequest(request);
            }
            return this;
        }
Called by the {@code WebSubject.Builder} constructor, this method places the request object in the
context map for later retrieval.

@param request the incoming ServletRequest that triggered the creation of the {@code WebSubject} instance.
@return 'this' for method chaining.
web/src/main/java/org/apache/shiro/web/subject/WebSubject.java