user2393012 user2393012 - 22 days ago 23
Java Question

How to return an image in Spring Boot controller and serve like a file system

I've tried the various ways given in Stackoverflow, maybe I missed something.

I have an Android client (whose code I can't change) which is currently getting an image like this:

HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();


Where
url
is the location of the image (static resource on CDN). Now my Spring Boot API endpoint needs to behave like a file resource in the same way so that the same code can get images from the API (Spring boot version 1.3.3).

So I have this:

@ResponseBody
@RequestMapping(value = "/Image/{id:.+}", method = RequestMethod.GET, consumes = MediaType.ALL_VALUE, produces = MediaType.IMAGE_JPEG_VALUE)
public ResponseEntity<byte[]> getImage(@PathVariable("id")String id) {
byte[] image = imageService.getImage(id); //this just gets the data from a database
return ResponseEntity.ok(image);
}


Now when the Android code tries to get
http://someurl/image1.jpg
I get this error in my logs:


Resolving exception from handler [public
org.springframework.http.ResponseEntity
com.myproject.MyController.getImage(java.lang.String)]:
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not
find acceptable representation


Same error happens when I plug
http://someurl/image1.jpg
into a browser.

Oddly enough my tests check out ok:

Response response = given()
.pathParam("id", "image1.jpg")
.when()
.get("MyController/Image/{id}");

assertEquals(HttpStatus.OK.value(), response.getStatusCode());
byte[] array = response.asByteArray(); //byte array is identical to test image


How do I get this to behave like an image being served up in the normal way? (Note I can't change the content-type header that the android code is sending)

EDIT

Code after comments (set content type, take out
produces
):

@RequestMapping(value = "/Image/{id:.+}", method = RequestMethod.GET, consumes = MediaType.ALL_VALUE)
public ResponseEntity<byte[]> getImage(@PathVariable("id")String id, HttpServletResponse response) {
byte[] image = imageService.getImage(id); //this just gets the data from a database
response.setContentType(MediaType.IMAGE_JPEG_VALUE);
return ResponseEntity.ok(image);
}


In a browser this just seems to give a stringified junk (byte to chars i guess). In Android it doesn't error, but the image doesn't show.

Answer

Finally fixed this... I had to add a ByteArrayHttpMessageConverter to my WebMvcConfigurerAdapter subclass:

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    final ByteArrayHttpMessageConverter arrayHttpMessageConverter = new ByteArrayHttpMessageConverter();
    final List<MediaType> list = new ArrayList<>();
    list.add(MediaType.IMAGE_JPEG);
    list.add(MediaType.APPLICATION_OCTET_STREAM);
    arrayHttpMessageConverter.setSupportedMediaTypes(list);
    converters.add(arrayHttpMessageConverter);

    super.configureMessageConverters(converters);
}