java – 添加c14n独占变换时,Xml签名无效

DOMSignContext dsc = new DOMSignContext
  (prk,xmldoc.getDocumentElement());

XMLSignatureFactory fac = 
  XMLSignatureFactory.getInstance("DOM");   

  DigestMethod digestMethod = 
      fac.newDigestMethod("http://www.w3.org/2000/09/xmldsig#sha1",null);
  C14NMethodParameterSpec spec = null;
  CanonicalizationMethod cm = fac.newCanonicalizationMethod(
      "http://www.w3.org/2001/10/xml-exc-c14n#",spec);
  SignatureMethod sm = fac.newSignatureMethod( 
      "http://www.w3.org/2000/09/xmldsig#rsa-sha1",null);
  ArrayList transformList = new ArrayList();
  TransformParameterSpec transformSpec = null;
  Transform envTransform =   fac.newTransform("http://www.w3.org/2000/09/xmldsig#enveloped-signature",transformSpec);
  Transform exc14nTransform = fac.newTransform(
      "http://www.w3.org/2001/10/xml-exc-c14n#",transformSpec);
transformList.add(exc14nTransform); 
transformList.add(envTransform);

 Reference ref = fac.newReference("",digestMethod,transformList,null,null);
 ArrayList refList = new ArrayList();
 refList.add(ref);
 SignedInfo si =fac.newSignedInfo(cm,sm,refList);

这会将引用验证视为错误,并将核心有效性视为错误.但是当我删除envTrasnform变量即fac.new Transform(“http://www.w3.org/2001/10/xml-exc-c14n#”,transformSpec)并使用以下代码执行时：

DOMSignContext dsc = new DOMSignContext
  (prk,null);
  ArrayList transformList = new ArrayList();
  TransformParameterSpec transformSpec = null;
  Transform envTransform = fac.newTransform(
      "http://www.w3.org/2000/09/xmldsig#enveloped-signature",transformSpec);
 transformList.add(envTransform);
 Reference ref = fac.newReference("",refList);

这使核心有效性和参考有效性成为现实.为什么会这样呢？我得到了这个代码形式this链接(创建包络签名部分的代码片段2).