sign XML with WS-Security

Hello,
I'm new to this forum but i need some help.
My problem is for signing a xml with the WS-Security Oasis specification
(it's: <wsse:security><ds:signature><ds....)
Actually i use the xws-security framework but i have a bug, look my code:

Code :

// Initialize the apache libraries
Init.init();
 
// Obtain security elements from the keystore
PrivateKey privateKey = keyEntry.getPrivateKey();
 
// Obtain a sample SOAPMessage from a file
FileInputStream fis = new FileInputStream(new File(fileName));
Document doc = XMLUtil.toDOMDocument(fis);
//SOAPMessage message = MyFileUtils.getMessageFromFile(doc);
MessageFactory fac = MessageFactory.newInstance();
MimeHeaders mimeHeaders = new MimeHeaders();
mimeHeaders.addHeader("Context-Value", null);
SOAPMessage message = fac.createMessage(mimeHeaders, new FileInputStream(fileName));
SOAPHeader header = message.getSOAPHeader();
SOAPBody body = message.getSOAPBody();
 
 
// Set the wsu:Id attribute to the Body
XMLUtil.setWsuIdAttr(body, "id-2");
 
 
// Create a WSSE context for the SOAP message
SecurableSoapMessage sssm = new SecurableSoapMessage(message);
 
 
// Create a security header for the message (<wsse:Security>)
SecurityHeader sh = sssm.findOrCreateSecurityHeader();
 
 
// Insert the certificate (<wsse:BinarySecurityToken>)
X509SecurityToken stoken = new X509SecurityToken(header.getOwnerDocument(), cert);
 
// Insert the keyinfo referring to the certificate (<ds:KeyInfo>)
KeyInfoHeaderBlock kihb = new KeyInfoHeaderBlock(header.getOwnerDocument());
SecurityTokenReference secTR = new SecurityTokenReference(header.getOwnerDocument());
kihb.addBinarySecret(stoken.getAsSoapElement());
sh.insertHeaderBlock(kihb);
 
 
// Insert the Signature block (<ds:Signature>)
SignatureHeaderBlock shb = new SignatureHeaderBlock(header.getOwnerDocument(),XMLSignature.ALGO_ID_SIGNATURE_RSA);
Transforms transforms = new Transforms(header.getOwnerDocument());
transforms.addTransform(CanonicalizationMethod.EXCLUSIVE);
 
 
shb.addSignedInfoReference("id-2", transforms, Constants.ALGO_ID_DIGEST_SHA1);
sh.insertHeaderBlock(shb);
 
 
// Digest all References (#MyId) in the SignedInfo, calculate the signature value
// and set it in the SignatureValue Element
javax.swing.JOptionPane.showMessageDialog(null, "PublicKey : "+privateKey.toString());
shb.sign(privateKey);
 
// Add the signature data to the header element
header.addChildElement(sh.getAsSoapElement());
 
 
// Save the signed SOAP message
FileOutputStream fos = new FileOutputStream(new File(signatureFileName));
message.writeTo(fos);
message.writeTo(System.out);

This code return a null exception at the line : shb.sign(privateKey)
Erreur code:

Code :

An error has occurred : java.lang.NullPointerException
java.lang.NullPointerException
	at com.sun.org.apache.xml.internal.security.utils.resolver.implementations.ResolverDirectHTTP.engineCanResolve(Unknown Source)
	at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.canResolve(Unknown Source)
	at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.getInstance(Unknown Source)
	at com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver.getInstance(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.Reference.getContentsBeforeTransformation(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.Reference.dereferenceURIandPerformTransforms(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.Reference.calculateDigest(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.Reference.generateDigestValue(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.Manifest.generateDigestValues(Unknown Source)
	at com.sun.org.apache.xml.internal.security.signature.XMLSignature.sign(Unknown Source)
	at com.sun.xml.wss.core.SignatureHeaderBlock.sign(SignatureHeaderBlock.java:189)
	at sign.Main.signedXML(Main.java:475)
	at sign.Main.main(Main.java:113)

Thank you.