Spring Boot Webflux - Set UTF-8 Encoding

Question

I've been working with Spring Boot 2.0.0.RC1 and use spring-boot-starter-webflux in order to build a REST Controller that returns a flux of text data.

@GetMapping(value = "/")
public Flux<String> getData(){
    return Flux.interval(Duration.ofSeconds(2))
        .map(l -> "Some text with umlauts (e.g. ä, ö, ü)...");
}

Since the text data contains some umlauts (eg ä, ö, ü), I would like to change the Content-Type header of the response from text/event-stream to text/event-stream;charset=UTF-8 . Therefore, I tried wrapping to flux into a ResponseEntity . Like this:

@GetMapping(value = "/")
public ResponseEntity<Flux<String>> getData(){
    return ResponseEntity
            .ok()
            .contentType(MediaType.parseMediaType("text/event-stream;charset=UTF-8"))
            .body(Flux.interval(Duration.ofSeconds(2))
                    .map(l -> "Some text with umlauts (e.g. ä, ö, ü)..."));
}

Now, making a curl request to the endpoint shows that the Content-Type remains the same:

< HTTP/1.1 200 OK
< transfer-encoding: chunked
< Content-Type: text/event-stream
<
data:Some text with umlauts (e.g. ├ñ, ├Â, ├╝)...

I suspected the MediaType.parseMediaType() method to be the issue, but the media type is parsed correctly (as this screenshot shows):

However, the parameter charset seems to be ignored. How can I change the encoding to UTF-8 so that the browser interprets the umlaut characters correctly?

EDIT: Setting within the GetMapping annotation the produces field does not work either.

@GetMapping(value = "/", produces = "text/event-stream;charset=UTF-8")
public ResponseEntity<Flux<String>> getData(){
    return ResponseEntity
            .accepted()
            .contentType(MediaType.parseMediaType("text/event-stream;charset=UTF-8"))
            .body(Flux.interval(Duration.ofSeconds(2))
                    .map(l -> "Some text with umlauts (e.g. ä, ö, ü)..."));
}

Answer 1

You can create a Filter and process response before this return to browser

    import java.io.IOException;
    
    import javax.servlet.Filter;
    import javax.servlet.FilterChain;
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    import org.springframework.core.Ordered;
    
    // esse filtro foi criado pra converter para UTF-8 o response do Flux<ServerSentEvent<String>>
// this filter was created to convert all responses to UTF8, including Flux<ServerSentEvent<String>>
    @Component
    @Order(Ordered.HIGHEST_PRECEDENCE)
    public class FluxPreProcessorFilter implements Filter {
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                throws IOException, ServletException {
            response.setCharacterEncoding("UTF-8");
            chain.doFilter(request, response);
        }
    
    }