I want to display an image in Java!

This is YuruFuwaFox. I'm studying Java. How can I display the image in Spring REST Controller this time? So I implemented it while researching various things, so I would like to share the method with a memo!

Annotation

This article is for quite a beginner in Java. I'm not for people who are Tsuyotsuyo engineers, so I would appreciate your favor. If you still read it, thank you! (Pointing out what is wrong is also welcome!)

Displaying an image with RESTController? ?? ??

First of all, what is RESTController? I will explain from. RESTController is for so-called API that returns JSON or xml as the return value. It's like passing only data to a normal Controller, which basically returns a View! In other words, if you want to return View, it seems that you can simply pass the image to View and display it somehow, but what should you do with RESTController that returns JSON or xml?

Pass data in binary format

Images can be displayed by passing them as binary data. Therefore, I decided to display the image by passing it in binary format.

Pass the data to HttpEntity and display the image

I will display the image on the browser. Therefore, I will use HttpEntity to put an image in the response body.

`showImgService.java`


public HttpEntity<[byte]> showImg(String image) throws IOException{
    //Image acquisition
    Resource resource = resourceLoader.getResource("File:" + staticPath + imgPath);
    //For image format acquisition
    String format;
    //For storing byte data
    ByteArrayOutputStream bout;
    //Image to byte data
    try (InputStream img = resource.getInputStream()) {
        format = URLConnection.guessContentTypeFromStream(img);

        bout = new ByteArrayOutputStream();
        int c;
        while ((c = img.read()) != -1) {
            bout.write(c);
        }
    }
    //Extract byte data
    byte[] bytes = bout.toByteArray();

    //Create header
    HttpHeaders headers = new HttpHeaders();
    //Store content information in the header
    headers.setContentType(MediaType.valueOf(format));
    headers.setContentLength(bytes.length);
    //Pass byte data and header to HttpEntity and return
    return new HttpEntity<>(bytes, headers);
}

At the end

It's really a memo, so it's a rough feeling. You can actually convert image byte data in one line by using IOUtils, but this time I forgot, so it looks like this. I hope it helps someone!

I want to display images with REST Controller of Java and Spring!