code: static DocumentBuilderFactory getDBF() {
          DocumentBuilderFactory dbf = threadDBF.get();
          if (dbf == null) {
              dbf = DocumentBuilderFactory.newInstance();
              dbf.setNamespaceAware(true);
              threadDBF.set(dbf);
          }
          return dbf;
      }
docs: Get a thread local DocumentBuilderFactory.
  <p>
  DocumentBuilderFactory is NOT thread safe. This method uses a thread
  local to create one per calling thread.
  
  @return The instance for this thread.