我试图解析具有声明为使用过渡性dtd的doctype的HTML文档，如下所示：

<！DOCTYPE html PUBLIC“-// W3C // DTD XHTML 1.0 Transitional // EN”“
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd
”>

在文档上执行Builder.build时，出现以下异常：

  java.io.IOException: Server returned HTTP response code: 503 for URL: http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd
       at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1305)
       at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
       at org.apache.xerces.impl.XMLEntityManager.startEntity(Unknown Source)
       at org.apache.xerces.impl.XMLEntityManager.startDTDEntity(Unknown Source)
       at org.apache.xerces.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
       at org.apache.xerces.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Unknown Source)
       at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
       at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
       at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
       at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
       at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
       at nu.xom.Builder.build(Builder.java:1127)
       at nu.xom.Builder.build(Builder.java:1019)

如果我删除文档类型声明，它就可以解析。我可以从浏览器成功下载dtd，它告诉我该URL有效。我不想删除文档类型声明。有没有一种方法告诉构建器不要下载dtd或为其提供备用dtd？