java 从数据库下载文件到 PC

Question

I am getting an image (jpeg or pdf) from a database and want to download it to the PC. However, the image is not recognised at .file.exists() . This points to File file = new File(resourceDetail.getResourseImage()); being incorrect. What is the correct way to code this please?

Note: resourceDetail.getResourseImage() is the actual image not a path.

My code is:

        resourceDetail = MySQLConnection.resourceDownload(fileID);

        FileInputStream stream = null;
        try {
            File file = new File(resourceDetail.getResourseImage());
            System.out.println("resourceDetail.getResourseImage(): " + resourceDetail.getResourseImage());

            if (!file.exists()) {
                System.out.println("File does not exist: ");
//              context.addMessage(new ErrorMessage("msg.file.notdownloaded"));
//              context.setForwardName("failure");
            } else {
                System.out.println("File exist: ");
                if (resourceDetail.getResourseImageType().equals("pdf")){
                    System.out.println("pdf: ");
                    response.setContentType("application/pdf");
                    response.setHeader("Content-Disposition", "attachment; filename='myfile.pdf'");
                }else{
                    System.out.println("jpeg: ");
                    response.setContentType("image/jpeg");
                    response.setHeader("Content-Disposition", "attachment; filename='myfile.jpg'");
                }
//              response.setHeader("Content-Disposition", "attachment; filename=" + file.getName());
                System.out.println("stream: ");
                stream = new FileInputStream(file);
                response.setContentLength(stream.available());
                OutputStream os = response.getOutputStream();      
                os.close();
                response.flushBuffer();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (stream != null) {
                try {
                    stream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

Answer 1

resourceDetail.getResourseImage() got string data, you can directly write the data to response by using: OuputStream#write(bytes) . In you case, just use ·os.write(resourceDetail.getResourseImage().getByets());` to do this.

The Sample code:

resourceDetail = MySQLConnection.resourceDownload(fileID);
try {
    System.out.println(
            "resourceDetail.getResourseImage(): " + resourceDetail.getResourseImage());

        if (resourceDetail.getResourseImageType().equals("pdf")) {
            System.out.println("pdf: ");
            response.setContentType("application/pdf");
            response.setHeader("Content-Disposition", "attachment; filename='myfile.pdf'");
        } else {
            System.out.println("jpeg: ");
            response.setContentType("image/jpeg");
            response.setHeader("Content-Disposition", "attachment; filename='myfile.jpg'");
        }
        response.setContentLength(resourceDetail.getResourseImage().length());
        OutputStream os = response.getOutputStream();
        os.write(resourceDetail.getResourseImage().getBytes());
        os.close();
        response.flushBuffer();
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (stream != null) {
        try {
            stream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 2

While this solution does not directly answer the issue with java it does give me a solution. I started with using jQuery which worked with Chrome and not IE. I was told it was not possible to active downloading images with jQuery and that I needed to do it via java. However, I have now found:

http://danml.com/download.html

Kind regards,

Glyn