NAVER WORKS

// claim 생성

String claim = String.format("{\"iss\":\"%s\",\"sub\":\"%s\",\"iat\":%d,\"exp\":%d}", client_id, service_account, iat, exp);

//String claim = String.format("{\"iss\":\"%s\",\"sub\":\"%s\",\"iat\":%d,\"exp\":%d}", "abcd", "46c4f281f81148c9b846c59262ae5888@example.com", 1634711358, 1634714958);

String base64_claim = Base64.getEncoder().encodeToString(claim.getBytes());

String jwt = String.format("%s.%s",base64_header,base64_claim);

// 암호화 키 조회

StringBuilder contentBuilder = new StringBuilder();

try (BufferedReader br = new BufferedReader(new FileReader(application.getRealPath("jwt_test.key")))) {

String line;

while ((line = br.readLine()) != null) {

contentBuilder.append(line).append("\n");

}

} catch (IOException e) {

e.printStackTrace();

}

String privateKeyString = contentBuilder.toString();

// 암호화 키 생성

byte[] privateKeyBytes = Base64.getDecoder().decode(privateKeyString.replaceAll("-----BEGIN PRIVATE KEY-----", "").replaceAll("-----END PRIVATE KEY-----", "").replaceAll("\\s+", ""));

PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);

KeyFactory keyFactory = KeyFactory.getInstance("RSA");

PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

// 암호화

Signature signature = Signature.getInstance("SHA256withRSA");

signature.initSign(privateKey);

signature.update(jwt.getBytes());

byte[] signatureBytes = signature.sign();

// base64 인코딩

String encodedSignature = Base64.getEncoder().encodeToString(signatureBytes);

// jws 생성

String jws = jwt + "." + encodedSignature;