如何在Java程序中设置SubjectAltName

import java.io.FileOutputStream;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.cert.Certificate;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.Date;
import java.util.Random;

import javax.security.auth.x500.X500Principal;

import sun.security.x509.AlgorithmId;
import sun.security.x509.CertificateAlgorithmId;
import sun.security.x509.CertificateExtensions;
import sun.security.x509.CertificateIssuerName;
import sun.security.x509.CertificateSerialNumber;
import sun.security.x509.CertificateSubjectName;
import sun.security.x509.CertificateValidity;
import sun.security.x509.CertificateVersion;
import sun.security.x509.Extension;
import sun.security.x509.GeneralName;
import sun.security.x509.GeneralNames;
import sun.security.x509.SubjectAlternativeNameExtension;
import sun.security.x509.SubjectKeyIdentifierExtension;
import sun.security.x509.X500Name;
import sun.security.x509.X509CertImpl;
import sun.security.x509.X509CertInfo;

public class SubjectAltNameExample {

    public static void main(String[] args) throws Exception {
        // 生成密钥对
        KeyPair keyPair = generateKeyPair();

        // 生成证书
        X509Certificate certificate = generateCertificate(keyPair);

        // 保存证书到文件
        saveCertificateToFile(certificate, "certificate.crt");
    }

    private static KeyPair generateKeyPair() throws Exception {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(2048);
        return keyPairGenerator.generateKeyPair();
    }

    private static X509Certificate generateCertificate(KeyPair keyPair) throws Exception {
        // 生成证书的基本信息
        X509CertInfo certInfo = new X509CertInfo();
        Date startDate = new Date();
        Date endDate = new Date(startDate.getTime() + 365 * 24 * 60 * 60 * 1000L); // 有效期为1年
        CertificateValidity validity = new CertificateValidity(startDate, endDate);
        BigInteger serialNumber = new BigInteger(64, new Random());
        X500Name issuer = new X500Name("CN=Issuer");
        X500Name subject = new X500Name("CN=Subject");

        certInfo.set(X509CertInfo.VALIDITY, validity);
        certInfo.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber(serialNumber));
        certInfo.set(X509CertInfo.ISSUER, new CertificateIssuerName(issuer));
        certInfo.set(X509CertInfo.SUBJECT, new CertificateSubjectName(subject));
        certInfo.set(X509CertInfo.KEY, new CertificateX509Key(keyPair.getPublic()));
        certInfo.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3));

        // 设置SubjectAltName扩展
        SubjectAlternativeNameExtension sanExtension = createSubjectAltNameExtension();
        certInfo.set(X509CertInfo.EXTENSIONS, new CertificateExtensions(new Extension[] { sanExtension }));

        // 使用私钥对证书进行签名
        AlgorithmId algorithmId = new AlgorithmId(AlgorithmId.sha256WithRSAEncryption_oid);
        X509CertImpl certificate = new X509CertImpl(certInfo);
        certificate.sign((PrivateKey) keyPair.getPrivate(), algorithmId);

        return certificate;
    }

    private static SubjectAlternativeNameExtension createSubjectAltNameExtension() throws CertificateException {
        GeneralName[] generalNames = new GeneralName[2];
        generalNames[0] = new GeneralName(GeneralName.dNSName, "example.com");
        generalNames[1] = new GeneralName(GeneralName.iPAddress, "192.168.0.1");

        GeneralNames subjectAltNames = new GeneralNames(generalNames);
        return new SubjectAlternativeNameExtension(false, subjectAltNames);
    }

    private static void saveCertificateToFile(X509Certificate certificate, String fileName) throws Exception {
        CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
        FileOutputStream fileOutputStream = new FileOutputStream(fileName);
        certificateFactory.generateCertificate(fileOutputStream);
        fileOutputStream.close();
    }
}