public static void main(String[] args) {        String subjectDN = "CN=duwenlei";        String algorithm = "";        try {            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");            keyPairGenerator.initialize(2048);            KeyPair keyPair = keyPairGenerator.generateKeyPair();            algorithm = keyPair.getPrivate().getAlgorithm();            PKCS10CertificationRequestBuilder builder = new PKCS10CertificationRequestBuilder(new X500Name(subjectDN)                    ,SubjectPublicKeyInfo.getInstance(keyPair.getPublic().getEncoded()));                        JcaContentSignerBuilder jcaBuilder = new JcaContentSignerBuilder("sha1withrsa");//            jcaBuilder.setProvider(provider); 这里可以添加提供者            ContentSigner contentSigner = jcaBuilder.build(keyPair.getPrivate());            builder.build(contentSigner);            System.out.println(builder.toString());        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        } catch (OperatorCreationException e) {            e.printStackTrace();        }    }