You need to write the image as a byte array to the response’s output stream. Something like this:
byte[] imageBytes = getImageAsBytes();
response.setContentType("image/jpeg");
response.setContentLength(imageBytes.length);
response.getOutputStream().write(imageBytes);
Then in you JSP you just use a standard img
element:
<img src="https://stackoverflow.com/questions/1154254/url to your servlet">