Curl: how data is interpreted by Java InputStream, if I sent it using curl --data-binary?

Question

I have a server, written on Java, which is currently running on a

http://localhost:8080

Source code is hidden from me, but I know that all endpoints are handled by Java HttpExchange class, for example endpoint:

http://localhost:8080/generate/init

will be handled like that:

public void init(HttpExchange httpex) throws IOException {
...
}

The next thing I know is that incoming POST requests are handled like that:

byte post_data = (byte) httpex.getRequestBody().read();

My question is, that when I do from a command-line:

echo -e '\x03' | curl -X POST -i --data-binary @- http://localhost:8080/generate/init

What will be the value of post_data? As I understand curl will send '\x03' exactly as it is:

\x03

And Java HttpExchange method getRequestBody() will return InputStream of it, where read() will translate that InputStream into int. As much as I know, Java doesn't interpret HEX as '\x03', instead it uses Unicode '\u0003'. Therefore I'm afraid of sending wrong data into my server.

If I'm wrong about curl --data-binary, please correct me! I just wish to be sure, that I pass number "3" by POST request and server interprets it as number 3, but in bytes ((byte) 3)