code: public static Resource getGenericResource(String resource) {
          log.trace("retrieving resource -> " + resource);
          try {
  
              final File file = normFile(resource);
              if (file.exists()) {
                  return new ResourceImpl(file.toURI().toURL());
              }
  
              if (resource.startsWith("/")) {
                  throw new IllegalArgumentException("Classpath resource cannot start with '/': " + resource);
              }
              if (resource.indexOf('\\') != -1) {
                  throw new IllegalArgumentException("Classpath resource cannot contain '\\': " + resource);
              }
              URL url = getLoader().getResource(resource);
              if (url == null) {
                  return null;
              }
              return new ResourceImpl(url);
          } catch (Exception e) {
              log.error("Could not retrieve resource: " + e.getMessage(), e);
              return null;
          }
      }
docs: Gets a generic resource, searching first from the file system then in the classpath if not found.
  
  @param resource The resource name
  @return The resource