rest - SprintBoot returning a PNG from a Controller's RequestMapping -

i've been scouring internet resources , feel have answer, can't quite seem bufferedimage returned browser window.

the project generates maze can create bufferedimage.

here code controller.

    @requestmapping(method = requestmethod.get, path = "/image", params = {"rows", "columns"})     public responseentity<byte[]> image(@requestparam(name = "rows") int rows, @requestparam(name = "columns") int columns) throws ioexception, interruptedexception {         try {             basiccartesiangrid requestedmaze = new basiccartesiangrid(rows, columns);             requestedmaze.foreach(cellalgorithms.binary_tree);             bufferedimage bufferedimage = requestedmaze.todisplayimage();             {   // dumping file debugging <- works expected                 file outputfile = new file("save.png");                 imageio.write(bufferedimage, "png", outputfile);             }             bytearrayoutputstream pngbytestream = new bytearrayoutputstream();             imageio.write(bufferedimage, "png", pngbytestream);             byte[] pngbytes = pngbytestream.tobytearray();             final httpheaders headers = new httpheaders();             headers.setcontenttype(mediatype.image_png);             headers.setcontentlength(pngbytes.length);             headers.setcachecontrol(cachecontrol.nocache().getheadervalue());              return new responseentity<>(pngbytes, headers, httpstatus.ok);         } catch (exception e) {             // hasn't occurred yet, in case             thread.sleep(1000);             system.err.println(e.getlocalizedmessage());              final httpheaders headers = new httpheaders();             headers.setcontenttype(mediatype.text_plain);             return new responseentity<>(e.getlocalizedmessage().getbytes("ascii"), headers, httpstatus.internal_server_error);         }     } 

i have ascertained png being generated correctly, file exists , viewable on hard-drive. browser gets broken image returned back. terminal, can more information.

curl "http://localhost:8080/maze/image?rows=10&columns=10" 

dumps out following (the quotation marks part of response, while data represented ellipsis changes request request, due fact each maze randomly generated , unique):

"ivborw0kggoaaaansuheugaaa......" 

i googled string prefix, , found this page. shows string should used data-uri, so:

<img src="data:image/png;base64,ivborw0kggoaaaansuheugaaa…" > 

i'm not sure go here. seems image being generated correctly, must missing header in response tell browser/spring these bytes should interpreted image , not string.

update: based on dialog between myself , shawn clark answer section, here have presently.

@springbootapplication @log4j public class springmazesapplication {      @bean     public httpmessageconverter<bufferedimage> bufferedimagehttpmessageconverter() {         log.debug("registering bufferedimage converter");         return new bufferedimagehttpmessageconverter();     }      public static void main(string[] args) throws ioexception {         springapplication.run(springmazesapplication.class, args);     } } 

and actual controller:

@controller @requestmapping(path = "/maze/basic", method = requestmethod.get) @log4j public class basicmazecontroller {      @requestmapping(params = {"format", "format=text"}, produces = mediatype.text_plain_value)     @responsebody     public string simplemazetext(@requestparam(name = "rows", defaultvalue = "10", required = false) int rows,                                  @requestparam(name = "columns", defaultvalue = "10", required = false) int columns) throws ioexception {         basiccartesiangrid requestedmaze = new basiccartesiangrid(rows, columns);         requestedmaze.foreach(cellalgorithms.binary_tree);         return requestedmaze.todisplaystring();     }      @requestmapping(params = {"format=image"}, produces = mediatype.image_png_value)     @responsebody     public bufferedimage simplemazeimage(@requestparam(name = "rows", defaultvalue = "10", required = false) int rows,                                          @requestparam(name = "columns", defaultvalue = "10", required = false) int columns) throws ioexception {         log.debug("starting image generation");         basiccartesiangrid requestedmaze = new basiccartesiangrid(rows, columns);         requestedmaze.foreach(cellalgorithms.binary_tree);         bufferedimage bufferedimage = requestedmaze.todisplayimage();         {   // dumping file debugging <- works expected             log.debug("dumping image hd");             file outputfile = new file("save.png");             imageio.write(bufferedimage, "png", outputfile);         }         log.debug("returning image generation");         return bufferedimage;     }      @requestmapping     @responsebody     public responseentity<string> simplemazeinvalid(@requestparam(name = "rows", defaultvalue = "10", required = false) int rows,                                                     @requestparam(name = "columns", defaultvalue = "10", required = false) int columns,                                                     @requestparam(name = "format") string format) throws ioexception {         final httpheaders headers = new httpheaders();         headers.setcontenttype(mediatype.text_plain);         return new responseentity<>("invalid format: " + format, headers, httpstatus.bad_request);     } } 

from terminal can curl -d - "url" , can see both logging/debugging , output terminal, converter registered @ begging of application , i'm getting responses expect actual image uri returns 406 not acceptable. if remove @responsebody image method, returns 500. can verify image generated being written disk expect should.

check out produces attribute on @requestmapping. want set image/png.

here complete example:

@restcontroller public class produceimage {     @getmapping(path = "/image", produces = "image/png")     public bufferedimage image() throws exception {         bufferedimage bufferedimage = imageio.read(new file("e:\\downloads\\skin_201305121633211421.png"));         return bufferedimage;     } } 

my bufferedimage computer can bufferedimage have requestedmaze.todisplayimage() without having other work. make work want include bufferedimagehttpmessageconverter in context.

@bean public httpmessageconverter<bufferedimage> bufferedimagehttpmessageconverter() {     return new bufferedimagehttpmessageconverter(); }