我正在尝试用java验证数字签名。下面是代码。

Document doc = convertStringToXMLDocument(message);
        NodeList nl = doc.getElementsByTagName(SIGNATURE);
        KeyStore ks = KeyStore.getInstance(JKS);
        Resource resource = resourceLoader.getResource("file.jks");

        ks.load(resource.getInputStream(), "Passwor".toCharArray());
        X509Certificate trustedcertificate = (X509Certificate) ks.getCertificate(alias);

        DOMValidateContext valContext = new DOMValidateContext(trustedcertificate.getPublicKey(),nl.item(0));
        valContext.setProperty("javax.xml.crypto.dsig.cacheReference", Boolean.TRUE);
        XMLSignature signature = fac.unmarshalXMLSignature(valContext);
        boolean coreValidity = signature.validate(valContext);

字符串到文档方法：

public static Document convertStringToXMLDocument(String xmlString) {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
         DocumentBuilder builder = null;
        try {
        factory.setNamespaceAware(true);
        builder = factory.newDocumentBuilder();
        Document doc = builder.parse(new InputSource(new StringReader(xmlString)));
        return doc;
      } catch (Exception e) {
        logger.error("Exception {} ", e.getMessage());
      }
       return null;
   }

这是工作正常的消息完美，但我的一个消息有笑脸在它。因此它表示无效消息（消息肯定有效）。有人能告诉我哪里出了问题吗。