Azure storage through java MVC web site

Question

I have a java web app using Spring and hibernate framework. I am moving this web app on azure. In on premises web app there is one functionality in which I upload the image first in a temporary folder in C: and later access that file for application. The location of uploaded file is also stored in DB for further references. I have defined the base-path for uploading file in a properties file and accessing through it in controller as well as service layer for creating the directory, file name and file path.

Can any tell me how to do the same in azure using azure storage? Any help is appreciated.

Code in properties file:

# Base File Path for Uploading Files 
fileupload.basepath=C:/webApp

Code for creating temporary folder

    @RequestMapping(value = "/file/upload", method = RequestMethod.POST)
public @ResponseBody
String upload(MultipartHttpServletRequest request,
        HttpServletResponse response) {

    // 0. notice, we have used MultipartHttpServletRequest

    // 1. get the files from the request object
    Iterator<String> itr = request.getFileNames();

    MultipartFile mpf = request.getFile(itr.next());

    if (!CommonUtil.isNull(mpf)) {
        if (mpf.getSize() > ProductCommonConstants.MAX_FILE_UPLOAD_SIZE_IN_BYTES) {
            return CommonConstants.STR_FAILURE;
        }

    }

    long fileName = Calendar.getInstance().getTimeInMillis();

    final String modelImageDirPath = baseUploadFilePath + "/"
            + CommonConstants.TEMP_FILE_NAME;

    // Check for folder existence
    final File modelImageDir = new File(modelImageDirPath);
    if (!modelImageDir.exists()) {
        // Create the directory
        modelImageDir.mkdirs();
    }

    InputStream is = null;
    FileOutputStream fos = null;

    try {
        String contentType = mpf.getContentType();

        if (contentType != null) {

            is = new DataInputStream(mpf.getInputStream());

            // just temporary save file info
            File file = new File(modelImageDirPath + "/" + fileName);

            fos = new FileOutputStream(file);

            // Write to the file
            IOUtils.copy(is, fos);
        }

    } catch (FileNotFoundException ex) {

    } catch (IOException ex) {

    } finally {

        try {
            if (fos != null) {
                fos.close();
            }
            if (is != null) {
                is.close();
            }
        } catch (IOException ignored) {
            // Log the Exception

        }
    }

    // 2. send it back to the client as <img> that calls get method
    // we are using getTimeInMillis to avoid server cached image

    return "/service/common/file/get/" + fileName;

}

}

Answer 1

Per my experience, you can use the upload(InputStream sourceStream, long length) of Class CloudBlob to upload files from Spring MVC MultipartFile to Azure Blob Storage, please see the code below modified from your code.

@RequestMapping(value = "/file/upload", method = RequestMethod.POST)
public @ResponseBody String upload(MultipartHttpServletRequest request,
        HttpServletResponse response) {
    // 0. notice, we have used MultipartHttpServletRequest
    // 1. get the files from the request object
    Iterator<String> itr = request.getFileNames();
    MultipartFile mpf = request.getFile(itr.next());
    if (!CommonUtil.isNull(mpf)) {
        if (mpf.getSize() > ProductCommonConstants.MAX_FILE_UPLOAD_SIZE_IN_BYTES) {
            return CommonConstants.STR_FAILURE;
        }
    }
    long fileName = Calendar.getInstance().getTimeInMillis();
    // Modified from your code: START
    String storageConnectionString = "DefaultEndpointsProtocol=http;" + "AccountName=your_storage_account;" + "AccountKey=your_storage_account_key";
    CloudStorageAccount storageAccount = CloudStorageAccount.parse(storageConnectionString);
    CloudBlobClient blobClient = storageAccount.createCloudBlobClient();
    CloudBlobContainer container = blobClient.getContainerReference("<blob-container-name>");
    InputStream is = null;
    try {
        String contentType = mpf.getContentType();
        if (contentType != null) {
            is = new DataInputStream(mpf.getInputStream());
            long length = mpf.getSize();
            CloudBlockBlob blob = container.getBlockBlobReference(""+fileName);
            blob.upload(is, length);
        }
    // Modified from your code: END
    } catch (FileNotFoundException ex) {

    } catch (IOException ex) {

    } finally {
        try {
            if (is != null) {
                is.close();
            }
        } catch (IOException ignored) {
            // Log the Exception

        }
    }   
    // 2. send it back to the client as <img> that calls get method
    // we are using getTimeInMillis to avoid server cached image
    return "/service/common/file/get/" + fileName;
}

For downloading or referencing the blob, you need to record the container name & blob name of the blob to the database.

OutputStream os = ...; // get the OutputStream from the HTTP Response
CloudBlobContainer container = blobClient.getContainerReference("<container-name>");
CloudBlob blob = getBlockBlobReference("<blob-name>");
blob.download(os)

For more information, you can refer to the Javadoc of Class CloudBlob http://azure.github.io/azure-storage-java/com/microsoft/azure/storage/blob/CloudBlob.html and the Get started doc for Blob Storage https://azure.microsoft.com/en-us/documentation/articles/storage-java-how-to-use-blob-storage/.