Unable to read Headers in AEM Cloud Dev environment

@aanchal-sikka 

It was /clientheaders where I had to allow the custom header. but then I got another error while trying to connect to the exchange token URL internally via servlet.

So basically I am first generating the JWT token using the privatekey.pem file and then hitting the exchange URL internally via servlet to generate the access token so that I can access the AEM author environment to access the resource.

String body = "client_id=" + URLEncoder.encode(clientId, "UTF-8") + "&" + "client_secret="
        + URLEncoder.encode(clientSecret, "UTF-8") + "&" + "jwt_token=" + URLEncoder.encode(jwtToken, "UTF-8");

try (DataOutputStream outputStream = new DataOutputStream(connection.getOutputStream())) {
    outputStream.writeBytes(body);
}

try (BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
    String inputLine;
    StringBuffer stringBuffer = new StringBuffer();
    while ((inputLine = in.readLine()) != null) {
        stringBuffer.append(inputLine);
    }
    response.getWriter().print(stringBuffer);
} 

I followed the below URL but not sure what is casuing the issue. do I have to allow my cloud instance to access EXCHANGE TOKEN url?

It's working well in localhost and breaking in DEV in second try statement.

https://techrevel.blog/2023/09/06/access-restricted-resources-on-aemaacs-with-java-and-service-accounts/