Sending Multiple images from web service SPRINGBOOT+REST+MAVEN - web-services

Question

I am writing a web service in spring boot restful web App using which i am sending a image to anyone who wants to consume it below is a code snippet which worked for me
#RequestMapping(value = "/photo_1",method = RequestMethod.GET )
public ResponseEntity<byte[]> greeting_image_1(#RequestParam(value="name", defaultValue="World") String name) throws IOException{
InputStream in = getClass().getResourceAsStream("/images/someimage.jpg");
byte[] a = IOUtils.toByteArray(in);
final HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.IMAGE_JPEG);
return new ResponseEntity<byte[]>(a,headers,HttpStatus.CREATED);
}
This web service works perfectly fine in case i want to return a single image from a web service
But what if in case i want to return array of images(i.e. more than 1 image)
Any help is highly appreciated.
Regards,

Answer 1

Here's the sample code that I wrote to generate a multipart response with multiple images in it. It's properly consumed by Firefox and it prompts to save each image in the response.
public ResponseEntity<byte[]> showImages () throws IOException {
String boundary="---------THIS_IS_THE_BOUNDARY";
List<String> imageNames = Arrays.asList(new String[]{"1.jpg","2.jpg"});
List<String> contentTypes = Arrays.asList(new String[]{MediaType.IMAGE_JPEG_VALUE,MediaType.IMAGE_JPEG_VALUE});
List<Byte[]> imagesData = new ArrayList<Byte[]>();
imagesData.add(ArrayUtils.toObject(IOUtils.toByteArray(getClass().getResourceAsStream("/images/1.jpg"))));
imagesData.add(ArrayUtils.toObject(IOUtils.toByteArray(getClass().getResourceAsStream("/images/2.jpg"))));
byte[] allImages = getMultipleImageResponse(boundary, imageNames,contentTypes, imagesData);
final HttpHeaders headers = new HttpHeaders();
headers.set("Content-Type","multipart/x-mixed-replace; boundary=" + boundary);
return new ResponseEntity<byte[]>(allImages,headers,HttpStatus.CREATED);
}
private static byte[] getMultipleImageResponse(String boundary, List<String> imageNames, List<String> contentTypes, List<Byte[]> imagesData){
byte[] finalByteArray = new byte[0];
Integer imagesCounter = -1;
for(String imageName : imageNames){
imagesCounter++;
String header="--" + boundary
+ "\r\nContent-Disposition: form-data; name=\"" + imageName
+ "\"; filename=\"" + imageName + "\"\r\n"
+ "Content-type: " + contentTypes.get(imagesCounter) + "\r\n\r\n";
byte[] currentImageByteArray=ArrayUtils.addAll(header.getBytes(), ArrayUtils.toPrimitive(imagesData.get(imagesCounter)));
finalByteArray = ArrayUtils.addAll(finalByteArray,ArrayUtils.addAll(currentImageByteArray, "\r\n\r\n".getBytes()));
if (imagesCounter == imageNames.size() - 1) {
String end = "--" + boundary + "--";
finalByteArray = ArrayUtils.addAll(finalByteArray, end.getBytes());
}
}
return finalByteArray;
}
You should implement this depending on the capability of the consumer. If the consumer can parse multipart response, please go ahead with this approach, else consider other options like
Sending a zipped file of all images
Returning a json/xml of image names along with URLs to download them
Returning a json/xml with all images in Base64 encoded string
You may also send a html response with all images embedded in it using the below code. This should work fine in all browsers as it is pure html.
public ResponseEntity<byte[]> getAllImages() throws IOException {
List<String> imageNames = Arrays.asList(new String[]{"1.jpg","2.jpg"});
List<String> contentTypes = Arrays.asList(new String[]{MediaType.IMAGE_JPEG_VALUE,MediaType.IMAGE_JPEG_VALUE});
List<Byte[]> imagesData = new ArrayList<Byte[]>();
imagesData.add(ArrayUtils.toObject(IOUtils.toByteArray(getClass().getResourceAsStream("/images/1.jpg"))));
imagesData.add(ArrayUtils.toObject(IOUtils.toByteArray(getClass().getResourceAsStream("/images/2.jpg"))));
byte[] htmlData=getHtmlData(imageNames,contentTypes, imagesData);
final HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.TEXT_HTML);
return new ResponseEntity<byte[]>(htmlData,headers,HttpStatus.OK);
}
private static byte[] getHtmlData(List<String> imageNames, List<String> contentTypes, List<Byte[]> imagesData){
String htmlContent="<!DOCTYPE html><html><head><title>Images</title></head><body>";
Integer imagesCounter = -1;
for(String imageName : imageNames){
imagesCounter++;
htmlContent = htmlContent + "<br/><br/><b>" + imageName + "</b><br/></br/><img src='data:" + contentTypes.get(imagesCounter) + ";base64, " + org.apache.commons.codec.binary.StringUtils.newStringUtf8(Base64
.encodeBase64(ArrayUtils.toPrimitive(imagesData.get(imagesCounter)))) + "'/>";
}
htmlContent = htmlContent + "</body></html>";
return htmlContent.getBytes();
}

Answer 2

You should take a look to "Uploading Files" Spring Boot guide : https://spring.io/guides/gs/uploading-files/
There's a an example of upload and download.