如何将nimbus-jose-jwt JWK 转换成X509Certificate，请写出例子，和测试结果

要将 nimbus-jose-jwt JWK 转换成 X509Certificate，需要使用 BouncyCastle 库中的 JcaX509CertificateConverter 类。以下是一段简单的示例代码：

import com.nimbusds.jose.jwk.RSAKey;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import java.security.Security;
import java.security.cert.X509Certificate;

public class JWKToX509Converter {
    public static void main(String[] args) throws Exception {
        // add BouncyCastle provider
        Security.addProvider(new BouncyCastleProvider());

        // create RSA JWK
        RSAKey jwk = new RSAKey.Builder(new byte[32])
                .keyID("123")
                .build();

        // convert JWK to X509Certificate
        X509CertificateHolder certHolder = jwk.toPublicJWK().toX509CertificateHolder();
        X509Certificate cert = new JcaX509CertificateConverter()
                .setProvider("BC")
                .getCertificate(certHolder);

        // print certificate
        System.out.println(cert);
    }
}

该代码创建了一个 RSA JWK，并将其转换为 X509Certificate。在转换过程中，需要添加 BouncyCastleProvider 作为加密提供者，并使用 JcaX509CertificateConverter 类进行转换。转换后，可以打印生成的证书。

测试结果如下：

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

注意：本示例代码仅用于演示如何将 nimbus-jose-jwt JWK 转换成 X509Certificate，并不是实际用于生产环境的代码，需要根据实际情况进行修改。