如何在 JAVA 的 rest API 中将图像返回给浏览器？

Question

我想在点击localhost:8080:/getImage/app/path={imagePath} 之类的 API 时获取图像

当我点击这个 API 时，它会返回一个图片。

这可能吗？

实际上，我已经尝试过了，但它给了我一个错误。 这是我的代码，

@GET
@Path("/app")
public BufferedImage getFullImage(@Context UriInfo info) throws MalformedURLException, IOException {
    String objectKey = info.getQueryParameters().getFirst("path");

    return resizeImage(300, 300, objectKey);
}


public static BufferedImage resizeImage(int width, int height, String imagePath)
        throws MalformedURLException, IOException {
    BufferedImage bufferedImage = ImageIO.read(new URL(imagePath));
    final Graphics2D graphics2D = bufferedImage.createGraphics();
    graphics2D.setComposite(AlphaComposite.Src);
    // below three lines are for RenderingHints for better image quality at cost of
    // higher processing time
    graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    graphics2D.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    graphics2D.drawImage(bufferedImage, 0, 0, width, height, null);
    graphics2D.dispose();
    System.out.println(bufferedImage.getWidth());
    return bufferedImage;
}

我的错误，

java.io.IOException: The image-based media type image/webp is not supported for writing

有什么方法可以在点击 java 中的任何 URL 时返回图像？

Answer 1

您可以使用IOUtils。这是代码示例。

@RequestMapping(path = "/getImage/app/path/{filePath}", method = RequestMethod.GET)
public void getImage(HttpServletResponse response, @PathVariable String filePath) throws IOException {
    File file = new File(filePath);
    if(file.exists()) {
        String contentType = "application/octet-stream";
        response.setContentType(contentType);
        OutputStream out = response.getOutputStream();
        FileInputStream in = new FileInputStream(file);
        // copy from in to out
        IOUtils.copy(in, out);
        out.close();
        in.close();
    }else {
        throw new FileNotFoundException();
    }
}

Answer 2

我没有测试它，因为我在这台机器上没有环境，但逻辑上它应该像下面这样工作，将它作为输入流读取并让你的方法返回@ResponseBody byte[]

@GET
@Path("/app")
public @ResponseBody byte[] getFullImage(@Context UriInfo info) throws MalformedURLException, IOException {
    String objectKey = info.getQueryParameters().getFirst("path");

    BufferedImage image = resizeImage(300, 300, objectKey);
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    ImageIO.write(image, "jpg", os);
    InputStream is = new ByteArrayInputStream(os.toByteArray());
    return IOUtils.toByteArray(is);
}

更新 根据@Habooltak Ana 的建议，不需要创建输入流，代码应如下所示

@GET
@Path("/app")
public @ResponseBody byte[] getFullImage(@Context UriInfo info) throws
MalformedURLException, IOException {
    String objectKey = info.getQueryParameters().getFirst("path");

    BufferedImage image = resizeImage(300, 300, objectKey);
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    ImageIO.write(image, "jpg", os);
    return os.toByteArray();
}

Answer 3

只需返回具有正确 HTTP 标头（Content-Type 和 Content-Disposition）的文件对象即可在大多数情况/环境中工作。

伪代码

File result = createSomeJPEG(); 
/*
 e.g.
 RenderedImage rendImage = bufferedImage;
 File file = new File("filename.jpg");
 ImageIO.write(rendImage, "jpg", file);
*/
response().setHeader("Content-Disposition", "attachment;filename=filename.jpg;");
response().setHeader("Content-Type", "image/jpeg");
return ok(result);

另见：

• file downloading in restful web services
• what's the correct way to send a file from REST web service to client?

Answer 4

这是一个简单的解决方案：

@GET
@Path("/somePath")
public void getImage(@Context HttpServletResponse res) throws IOException {
    java.nio.file.Path path = Paths.get("filePath");
    res.getOutputStream().write(Files.readAllBytes(path));
    res.getOutputStream().flush();
}