public ResponseEntity selectAvaliable(){

    List<Movie> moviesList = new ArrayList<>();

    //code that retrieves data from db, not important to my question
    for(Movie movie : movieRepository.selectAvailable())
        moviesList.add(movie);

    //this is where I set headers for caching:
    return ResponseEntity.status(HttpStatus.OK)
            .header("Cache-Control", "max-age=120")
            .header("ETag", new Timestamp(System.currentTimeMillis()).toString())
            .body(moviesList);
}