토큰 발급 Server returned HTTP response code: 401 for URL: https://kauth.kakao.com/oauth/token

REST API
1

앱 id 1012404

토큰 발급 시 Server returned HTTP response code: 401 for URL: https://kauth.kakao.com/oauth/token
java.lang.RuntimeException: 카카오 토큰 요청 중 오류가 발생했습니다.
에러가 발생합니다. Client Secret은 비활성화 상태입니다.

	public String getToken(String code) throws IOException {
		try {
			String access_Token = "";
			final String reqURL = "https://kauth.kakao.com/oauth/token";
			URL url = new URL(reqURL);
			HttpURLConnection urlCon = (HttpURLConnection) url.openConnection();
			urlCon.setRequestMethod("POST");
			urlCon.setDoOutput(true);
try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(urlCon.getOutputStream()))) {
				StringBuilder sb = new StringBuilder();
				sb.append("grant_type=authorization_code");
				sb.append("client_id=REST API 키");
				sb.append("&redirect_uri=Redirect URI");
				sb.append("&code=" + code);
				bw.write(sb.toString());
				bw.flush();
				bw.close();
			}
2

아래 내용 참고하셔서 에러 Body 확인해주시겠어요?

			BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
			String line = "";
			while ((line = br.readLine()) != null) {
				result += line;
			}
			System.out.println("response body : " + result);