JKStoBase64String.java

public class JKStoBase64String {
    private static final int BUFFER_SIZE = 65535;

    public static byte[] convertFileToByteArray(String certificateFilePath) throws Exception {
        if (certificateFilePath == null || certificateFilePath.isEmpty()) {
            throw new Exception("file path should not be null or empty");
        }
        File file = new File(certificateFilePath);
        if (!file.exists()) {
            throw new Exception("file not exist : " + file.getAbsolutePath());
        }
        if (file.isDirectory()) {
            throw new Exception("File shouldn't be a directory : " + file.getAbsolutePath());
        }
        try (InputStream inputStream = new FileInputStream(file)) {
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            byte[] buffer = new byte[BUFFER_SIZE];
            int numberOfReadBytes;
            while ((numberOfReadBytes = inputStream.read(buffer)) > 0) {
                byteArrayOutputStream.write(buffer, 0, numberOfReadBytes);
            }
            byte[] certificateInBytes = byteArrayOutputStream.toByteArray();
            Encoder encoder = Base64.getEncoder();
            byte[] encodedBytes = encoder.encode(certificateInBytes);
            return encodedBytes;
        }
    }

    /**
     * Convert the certificate into base64 encoded string.
     *
     * @param certificateFilePath
     * @return
     * @throws Exception
     */
    public static String convertJKSToString(String certificateFilePath) throws Exception {
        byte[] encodedBytes = convertFileToByteArray(certificateFilePath);
        String str = new String(encodedBytes);
        return str;
    }

    public static void main(String[] args) {
        String certificateInfo;
        try {
            System.out.println("===============KEYSTORE================");

            // for windows it would be like C:/path/to/file.jks
            certificateInfo = JKStoBase64String.convertJKSToString("/path/to/client-keystore.jks");
            System.out.println(certificateInfo);

            System.out.println("===============TRUSTSTORE================");

            // for windows it would be like C:/path/to/file.jks
            certificateInfo = JKStoBase64String.convertJKSToString("/path/to/client-truststore.jks");
            System.out.println(certificateInfo);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}