Spring @ExceptionHandler and HttpMediaTypeNotAcceptableException

The problem lies in the incompatibility of the requested content type and the object being returned. See my response on how to configure the ContentNegotiationConfigurer so that Spring determines the requested content type according to your needs (looking at the path extension, URL parameter or Accept header).

Depending on how the requested content type is determined, you have following options when an image is requested by the client:

• if the requested content type is determined by the Accept header, and if the client can/wants to handle a JSON response instead of the image data, then the client should send the request with Accept: image/*, application/json. That way Spring knows that it can safely return either the image byte data or the error JSON message.
• in any other case your best solution is to just return a HTTP error code, without any error message. You can do that in a couple of ways in your controller:

Set the error code on the response directly

public byte[] getImage(HttpServletResponse resp) {    try {        // return your image    } catch (Exception e) {        resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);    }}

Use ResponseEntity

public ResponseEntity<?> getImage(HttpServletResponse resp) {    try {        byte[] img = // your image        return ReponseEntity.ok(img);    } catch (Exception e) {        return new ResponseEntity(HttpStatus.INTERNAL_SERVER_ERROR);    }}

Use a separate @ExceptionHandler method in that controller, which will override the default Spring exception handling. That assumes you have either a dedicated exception type for image requests or a separate controller just for serving the images. Otherwise, the exception handler will handle exceptions from other endpoints in that controller, too.

What does your ExceptionInfo class look like? I run into quite similar issue after defining a few exception handlers in @ControllerAdvice annotated class. When exception happened it was caught, although the response was not return and org.springframework.web.HttpMediaTypeNotAcceptableException: Could not find acceptable representation was thrown.

I figured out that the problem was caused by the fact, that I missed to add getter methods to my ErrorResponse class. After adding getter methods (this class was immutable, so there were no setter methods) everything worked like a charm.

If you are willing to ignore the explicit instruction of your client, as expressed in the Accept header, you can tinker with the content negotiation strategy like so:

/** * Content negotiation strategy that adds the {@code application/json} media type if not present in the "Accept" * header of the request. * <p> * Without this media type, Spring refuses to return errors as {@code application/json}, and thus not return them at * all, which leads to a HTTP status code 406, Not Acceptable */class EnsureApplicationJsonNegotiationStrategy extends HeaderContentNegotiationStrategy {    @Override    public List<MediaType> resolveMediaTypes(NativeWebRequest request) throws HttpMediaTypeNotAcceptableException {        List<MediaType> mediaTypes = new ArrayList<>(super.resolveMediaTypes(request));        if (notIncludesApplicationJson(mediaTypes)) {            mediaTypes.add(MediaType.APPLICATION_JSON);        }        return mediaTypes;    }    private boolean notIncludesApplicationJson(List<MediaType> mediaTypes) {        return mediaTypes.stream()                .noneMatch(mediaType -> mediaType.includes(MediaType.APPLICATION_JSON));    }}

Use this in a @Configuration class like so:

@Configurationpublic class ContentNegotiationConfiguration implements WebMvcConfigurer {    @Override    public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {        configurer.strategies(List.of(                new EnsureApplicationJsonNegotiationStrategy()        ));    }}

Unit tests (using JUnit 5, Mockito):

@ExtendWith(MockitoExtension.class)public class EnsureApplicationJsonNegotiationStrategyTest {    @Mock    private NativeWebRequest request;    @InjectMocks    private EnsureApplicationJsonNegotiationStrategy subject;    @Test    public void testAddsApplicationJsonToAll() throws HttpMediaTypeNotAcceptableException {        when(request.getHeaderValues(HttpHeaders.ACCEPT)).thenReturn(new String[]{"*/*"});        assertThat(subject.resolveMediaTypes(request), contains(                MediaType.ALL // this includes application/json, so... fine        ));    }    @Test    public void testAddsApplicationJsonToEmpty() throws HttpMediaTypeNotAcceptableException {        when(request.getHeaderValues(HttpHeaders.ACCEPT)).thenReturn(new String[0]);        assertThat(subject.resolveMediaTypes(request), contains(                MediaType.ALL // that's what the default does, which includes application/json, so... fine        ));    }    @Test    public void testAddsApplicationJsonToExisting() throws HttpMediaTypeNotAcceptableException {        when(request.getHeaderValues(HttpHeaders.ACCEPT)).thenReturn(new String[]{"application/something"});        assertThat(subject.resolveMediaTypes(request), containsInAnyOrder(                MediaType.valueOf("application/something"),                MediaType.APPLICATION_JSON        ));    }    @Test    public void testAddsApplicationJsonToNull() throws HttpMediaTypeNotAcceptableException {        when(request.getHeaderValues(HttpHeaders.ACCEPT)).thenReturn(null);        assertThat(subject.resolveMediaTypes(request), contains(                MediaType.ALL // that's what the default does, which includes application/json, so... fine        ));    }    @Test    public void testRetainsApplicationJson() throws HttpMediaTypeNotAcceptableException {        when(request.getHeaderValues(HttpHeaders.ACCEPT)).thenReturn(new String[]{"application/json"});        assertThat(subject.resolveMediaTypes(request), contains(MediaType.APPLICATION_JSON));    }}