java - 使用特定的 xpointer 参考 Java 对 XML 进行签名

Question

我需要用 Java 中的以下参考 URI 对 XML 文档进行签名：

xpointer(//*[@authenticate='true'])

因此，我尝试使用此参考对其进行签名：

    Reference ref = fac.newReference
 ("#xpointer(//*[@authenticate='true'])", fac.newDigestMethod(DigestMethod.SHA256, null),
  Collections.singletonList
   (fac.newTransform
    ("http://www.w3.org/2001/10/xml-exc-c14n#", (TransformParameterSpec) null)),
     null, null);

我得到这个错误：

找不到 URI #xpointer(//*[@authenticate='true']) 和 Base null 的解析器

我在网上搜索如何修复它，我找到了这个类：

    public class XPointerResourceResolver extends ResourceResolverSpi
{
    private static Log log = LogFactory.getLog(XPointerResourceResolver.class);
    
    private static final String XP_OPEN = "xpointer(";
    private static final String XNS_OPEN = "xmlns(";
    
    private XPathFactory xPathFactory;
    private Node baseNode;
    
    public XPointerResourceResolver(Node baseNode)
    {
        this.xPathFactory = XPathFactory.newInstance();
        this.baseNode = baseNode;
    }
    
    /* (non-Javadoc)
     * @see org.apache.xml.security.utils.resolver.ResourceResolverSpi#engineCanResolve(org.w3c.dom.Attr, java.lang.String)
     */
    @Override
    public boolean engineCanResolve(Attr uri, String BaseURI)
    {
        String v = uri.getNodeValue();
        
        if (v.charAt(0) != '#')
            return false;
        
        String xpURI;
        try
        {
            xpURI = URLDecoder.decode(v, "utf-8");
        } catch (UnsupportedEncodingException e)
        {
            log.warn("utf-8 not a valid encoding",e);
            return false;
        }
        
        String parts[] = xpURI.substring(1).split("\\s");
        
        // plain ID reference.
        if (parts.length == 1 && !parts[0].startsWith(XNS_OPEN))
            return true;
        
        int i=0;
        
        for (;i<parts.length-1;++i)
            if (!parts[i].endsWith(")") ||  !parts[i].startsWith(XNS_OPEN))
                    return false;
            
        if (!parts[i].endsWith(")") || !parts[i].startsWith(XP_OPEN))
                return false;
        
        log.debug("xpURI="+xpURI);
        log.debug("BaseURI="+BaseURI);

        return true;
    }

    /* (non-Javadoc)
     * @see org.apache.xml.security.utils.resolver.ResourceResolverSpi#engineResolve(org.w3c.dom.Attr, java.lang.String)
     */
    @Override
    public XMLSignatureInput engineResolve(Attr uri, String BaseURI) throws ResourceResolverException
    {
        String v = uri.getNodeValue();
        
        if (v.charAt(0) != '#')
            return null;
        
        String xpURI;
        try
        {
            xpURI = URLDecoder.decode(v, "utf-8");
        } catch (UnsupportedEncodingException e)
        {
            log.warn("utf-8 not a valid encoding",e);
            return null;
        }
        
        String parts[] = xpURI.substring(1).split("\\s");
        
        int i=0;

        DSigNamespaceContext nsContext=null;
        
        if (parts.length > 1)
        {
            nsContext= new DSigNamespaceContext();
            
            for (;i<parts.length-1;++i)
            {
                if (!parts[i].endsWith(")") ||  !parts[i].startsWith(XNS_OPEN))
                    return null;
                
                String mapping = parts[i].substring(XNS_OPEN.length(),parts[i].length()-1);
                
                int pos = mapping.indexOf('=');
                
                if (pos <= 0 || pos >= mapping.length()-1)
                    throw new ResourceResolverException("malformed namespace part of XPointer expression",uri,BaseURI);
                
                nsContext.addNamespace(mapping.substring(0,pos), 
                                       mapping.substring(pos+1));
            }
        }
            
        try
        {
            Node node = null;
            NodeList nodes=null;
        
            // plain ID reference.
            if (i==0 && !parts[i].startsWith(XP_OPEN))
            {
                node = this.baseNode.getOwnerDocument().getElementById(parts[i]);
            }
            else
            {
                if (!parts[i].endsWith(")") || !parts[i].startsWith(XP_OPEN))
                    return null;
                
                XPath xp = this.xPathFactory.newXPath();
        
                if (nsContext != null)
                    xp.setNamespaceContext(nsContext);
            
                nodes =
                    (NodeList)xp.evaluate(parts[i].substring(XP_OPEN.length(),parts[i].length()-1),
                                          this.baseNode,
                                          XPathConstants.NODESET);
                
                if (nodes.getLength() == 0) return null;
                if (nodes.getLength() == 1)
                    node = nodes.item(0);
            }
        
            XMLSignatureInput result = null;
                        
            if (node != null)
            {
                 result = new XMLSignatureInput(node);
            }
            else if (nodes !=null)
            {
                Set<Node> nodeSet = new HashSet<Node>(nodes.getLength());
            
                for (int j=0 ; j<nodes.getLength(); ++j)
                {
                    nodeSet.add(nodes.item(j));
                }
                
                result = new XMLSignatureInput(nodeSet);
            }
            else
                return null;
            
            result.setMIMEType("text/xml");
            result.setExcludeComments(true);
            result.setSourceURI((BaseURI != null) ? BaseURI.concat(v):v);      

            return result;
            
        } catch (XPathExpressionException e)
        {
            throw new ResourceResolverException("malformed XPath inside XPointer expression",e,uri,BaseURI);
        }
    }
}

但是我没有找到如何使用它来使用我的 xpointer 对我的 XML 文档进行签名。