code: public void doDynamic(StaplerRequest req, StaplerResponse rsp) throws IOException, ServletException {
          String path = req.getRestOfPath();
          if (path.charAt(0)=='/') path = path.substring(1);
  
          if(!allowedResources.containsKey(path)) {
              if(!allowResourceToBeServed(path)) {
                  rsp.sendError(SC_FORBIDDEN);
                  return;
              }
              // remember URLs that we can serve. but don't remember error ones, as it might be unbounded
              allowedResources.put(path,path);
          }
  
          URL res = classLoader.getResource(path);
          if(res==null) {
              throw HttpResponses.error(SC_NOT_FOUND,new IllegalArgumentException("No such adjunct found: "+path));
          } else {
              long expires = MetaClass.NO_CACHE ? 0 : expiration;
              rsp.serveFile(req,res,expires);
          }
      }
docs: Serves resources in the class loader.