code: public String render(File file, Object... args) {
          try {
              if (!file.exists())
                throw new RuntimeException("template '"+file.getName()+"' does not exist!");
              if (!file.canRead())
                throw new RuntimeException("template '"+file.getName()+"' not readable!");
              ITemplate t = getTemplate(file, args);
              if (t==null)
                throw new RuntimeException("template '"+file.getName()+"' load failed!");
              return t.render();
          } finally {
              renderCleanUp();
          }
      }
docs: Render template with source specified by {@link java.io.File file instance}
  and an array of render args. Render result return as a String
  <p/>
  <p>See {@link #getTemplate(java.io.File, Object...)} for note on
  render args</p>
  
  @param file the template source file
  @param args render args array
  @return render result