如何使用 JAVA 从 REST API 调用打印/读取图像

Question

I have one REST URL which if I use in postman it gives me image in response. Now, I'm trying to see the same thing with JAVA code in Eclipse. (I'm looking for either saving image file or showing with JFrame or Applet etc.)

    String url = "https://test-api.com/v1/abc.jpg";

    // Creating URL Connection
    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    
    // Defining the request method. It can be GET, POST, PUT, DELETE
    con.setRequestMethod("GET");
    
    // Getting the HTTP Response code like 200, 404 etc.
    int responseCode = con.getResponseCode();
    System.out.println("\nSending 'GET' request to URL : " + url + "\n");
    System.out.println("Response Code : " + responseCode + "\n");
    
    // Saving response in the Stringbuffer
    BufferedReader in = new BufferedReader(
            new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();
    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();
    
    
    byte bytes[] = String.valueOf(response).getBytes();
    
    InputStream inS = new ByteArrayInputStream(bytes);
    int width = 963;    //width of the image
    int height = 640;   //height of the image
    BufferedImage image = null;
    image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    BufferedImage bImageFromConvert = ImageIO.read(inS);    
    

When I run the code, I get the exception like below.

javax.imageio.IIOException: Invalid JPEG file structure: two SOI markers
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.readImageHeader(Native Method)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.readNativeHeader(JPEGImageReader.java:628)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.checkTablesOnly(JPEGImageReader.java:347)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.gotoImage(JPEGImageReader.java:495)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.readHeader(JPEGImageReader.java:621)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.readInternal(JPEGImageReader.java:1078)
    at com.sun.imageio.plugins.jpeg.JPEGImageReader.read(JPEGImageReader.java:1058)
    at javax.imageio.ImageIO.read(ImageIO.java:1448)
    at javax.imageio.ImageIO.read(ImageIO.java:1352)

Response code comes 200. So, not sure what I'm doing wrong here. Why ImageIO cannot read the inputstream and picking up two SOI marker.

Answer 1

To show an image on the browser using jax-rs you can use this method with the hypothese that you have images folder under resources in your classpath:

@GET
@Path("image")
@Produces({"image/jpeg"})
public Response getImage() {
    BufferedImage image = null;
    byte[] imageData = null;
    try {
        //System.out.println("chemin courant : " + ClassLoader.getSystemClassLoader().
        //      getResource(".").getPath());
        image = ImageIO.read(ClassLoaderTestResource.class
                        .getResourceAsStream("/images/yourimage.jpg"));
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ImageIO.write(image, "png", baos);
        imageData = baos.toByteArray();
    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println("image : "+ image);
    System.out.println("Image data : "+ imageData);
    return Response.ok(new ByteArrayInputStream(imageData)).build();
}

so if you call http://localhost:8080/image for example you will have your image in the browser.