IOUtils.closeStream(writer);

进入代码

public static void closeStream(java.io.Closeable stream) {
	cleanup(null, stream);
}

public static void cleanup(Log log, java.io.Closeable... closeables) {
  for (java.io.Closeable c : closeables) {
    if (c != null) {
      try {
        c.close();
      } catch(IOException e) {
        if (log != null && log.isDebugEnabled()) {
          log.debug("Exception in closing " + c, e);
        }
      }
    }
  }
}