用JAVA代码实现把 PEM 格式的密钥转换为 pkcs8 格式

可以使用 BouncyCastle 库来实现将 PEM 格式的密钥转换为 pkcs8 格式。下面是一个示例代码：

import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.openssl.jcajce.JceOpenSSLPKCS8EncryptorBuilder;
import org.bouncycastle.operator.InputDecryptorProvider;
import org.bouncycastle.operator.OperatorCreationException;
import org.bouncycastle.operator.OutputEncryptor;
import org.bouncycastle.operator.bc.BcDefaultDigestProvider;
import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfo;
import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfoBuilder;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyPair;
import java.security.PrivateKey;

public class PemToPkcs8 {

    public static void main(String[] args) throws Exception {
        String pemFilePath = "path_to_pem_file";
        String pkcs8FilePath = "path_to_pkcs8_file";
        String password = "password";

        // 读取 PEM 格式的密钥
        InputStream pemInputStream = Files.newInputStream(Paths.get(pemFilePath));
        JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
        KeyPair keyPair = converter.getKeyPair(converter.getPrivateKey(Files.newBufferedReader(Paths.get(pemFilePath))));

        // 转换成 PKCS8 格式的密钥
        PrivateKey privateKey = keyPair.getPrivate();
        PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(privateKey.getEncoded());
        PKCS8EncryptedPrivateKeyInfoBuilder builder = new PKCS8EncryptedPrivateKeyInfoBuilder(privateKeyInfo);
        JceOpenSSLPKCS8EncryptorBuilder encryptorBuilder = new JceOpenSSLPKCS8EncryptorBuilder(PKCS8EncryptedPrivateKeyInfo.AES_256_CBC);
        encryptorBuilder.setProvider("BC");
        encryptorBuilder.setPasssword(password.toCharArray());
        OutputEncryptor encryptor = encryptorBuilder.build();
        InputDecryptorProvider decProv = encryptorBuilder.build(new BcDefaultDigestProvider());

        PKCS8EncryptedPrivateKeyInfo encryptedPrivateKeyInfo = builder.build(encryptor);
        byte[] pkcs8Encoded = encryptedPrivateKeyInfo.getEncoded();

        // 将 PKCS8 格式的密钥写入文件
        FileOutputStream fos = new FileOutputStream(pkcs8FilePath);
        fos.write(pkcs8Encoded);
        fos.close();
    }
}

在上面的代码中，需要将 `pemFilePath` 替换为 PEM 格式的密钥文件路径，将 `pkcs8FilePath` 替换为要存储 PKCS8 格式的密钥的文件路径，将 `password` 替换为用于加密 PKCS8 密钥的密码。

代码中使用的 BouncyCastle 版本是 1.69，你需要确保在项目中添加了相应的依赖库。