Spring 3 MVC, stream response asynchronously - spring

Question

I'd like to stream out my content using OutputStream or Writer from Spring MVC controller method using async solution, i.e. not to block base threadpool used for http requests. As far as I could find is to use DefferedResult<?> for async in general. It's fine when you return a view string name but can't think of a way it would work with stream. Could not find anything helpful.
Thanks

Answer 1

As described here you can perform computation in another thread thereby unloded http thread pool.
You can try to combine DefferedResult and byte[] (DefferedResult) return type(previously registering ByteArrayHttpMessageConverter). So the final method will look like this:
#ResponseBody
public DefferedResult<byte[]> foo(HttpServlet response) {
//set headers using response
response.setContentType("someContentType");
...
DefferedResult<byte[]> r = new DefferedResult<>();
executionService.submit(() -> {
r.setResult(getBytes());
});
return r;
}
Another option is to combine Defferedresult and ResponseEntity. Do not forget to use it in servlet 3.0+ container

Answer 2

It may be that what you are looking for is the following. Not sure if it blocks the http thread pool though.
#Controller
public class TestController {
#RequestMapping("/")
public StreamingResponseBody handleRequest () {
return new StreamingResponseBody() {
#Override
public void writeTo (OutputStream out) throws IOException {
for (int i = 0; i < 1000; i++) {
out.write((Integer.toString(i) + " - ")
.getBytes());
out.flush();
try {
Thread.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
}
}