如何在java中对xml文件进行包络数字签名？

import javax.xml.crypto.dsig.*;
import javax.xml.crypto.dsig.dom.DOMSignContext;
import javax.xml.crypto.dsig.keyinfo.KeyInfo;
import javax.xml.crypto.dsig.keyinfo.KeyInfoFactory;
import javax.xml.crypto.dsig.keyinfo.X509Data;
import javax.xml.crypto.dsig.spec.C14NMethodParameterSpec;
import javax.xml.crypto.dsig.spec.TransformParameterSpec;
import javax.xml.parsers.DocumentBuilderFactory;
import java.security.*;
import java.security.cert.Certificate;
import java.util.Collections;

public class XMLDigitalSignature {

    public static void main(String[] args) throws Exception {
        // 加载XML文档
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setNamespaceAware(true);
        org.w3c.dom.Document doc = dbf.newDocumentBuilder().parse("input.xml");

        // 创建XML签名工厂
        XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM");

        // 创建私钥和证书
        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
        ks.load(XMLDigitalSignature.class.getResourceAsStream("keystore.jks"), "password".toCharArray());
        KeyStore.PrivateKeyEntry keyEntry = (KeyStore.PrivateKeyEntry) ks.getEntry("alias", new KeyStore.PasswordProtection("password".toCharArray()));
        PrivateKey privateKey = keyEntry.getPrivateKey();
        Certificate cert = keyEntry.getCertificate();

        // 创建签名方法
        SignatureMethod signatureMethod = fac.newSignatureMethod("http://www.w3.org/2000/09/xmldsig#rsa-sha1", null);

        // 创建签名引用
        Reference ref = fac.newReference("", fac.newDigestMethod(DigestMethod.SHA1, null),
                Collections.singletonList(fac.newTransform(Transform.ENVELOPED, (TransformParameterSpec) null)), null, null);

        // 创建签名
        SignedInfo si = fac.newSignedInfo(fac.newCanonicalizationMethod(CanonicalizationMethod.INCLUSIVE,
                (C14NMethodParameterSpec) null), signatureMethod, Collections.singletonList(ref));

        // 创建KeyInfo
        KeyInfoFactory kif = fac.getKeyInfoFactory();
        X509Data x509Data = kif.newX509Data(Collections.singletonList(cert));
        KeyInfo ki = kif.newKeyInfo(Collections.singletonList(x509Data));

        // 创建签名上下文
        DOMSignContext dsc = new DOMSignContext(privateKey, doc.getDocumentElement());

        // 创建XML签名
        XMLSignature signature = fac.newXMLSignature(si, ki);
        signature.sign(dsc);

        // 将签名添加到XML文档
        org.w3c.dom.Element root = doc.getDocumentElement();
        root.appendChild(signature.getElement());

        // 保存签名后的XML文档
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer trans = tf.newTransformer();
        trans.transform(new DOMSource(doc), new StreamResult("output.xml"));
    }
}