如何在不将文件保存在本地存储上的情况下将对象传输到 Azure Blob 存储？

Posted 2023-04-13

【中文标题】如何在不将文件保存在本地存储上的情况下将对象传输到 Azure Blob 存储？

【英文标题】：How to transfer objects to Azure Blob Storage without saving file on local storage?

【发布时间】：2020-02-04 06:23:10

【问题描述】：

我一直关注此example from GitHub 将文件传输到 Azure Blob 存储。该程序在本地 MyDocuments 文件夹中创建一个文件以上传到 blob 容器。创建文件后，它会将其上传到容器中。是否可以在内存中创建 JSON 对象并将它们发送到 Azure Blob 存储，而无需先将该文件写入硬盘驱动器？

namespace storage_blobs_dotnet_quickstart

    using Microsoft.Azure.Storage;
    using Microsoft.Azure.Storage.Blob;
    using System;
    using System.IO;
    using System.Threading.Tasks;

    public static class Program
    
        public static void Main()
        
            Console.WriteLine("Azure Blob Storage - .NET quickstart sample");
            Console.WriteLine();
            ProcessAsync().GetAwaiter().GetResult();

            Console.WriteLine("Press any key to exit the sample application.");
            Console.ReadLine();
        

        private static async Task ProcessAsync()
        
            CloudStorageAccount storageAccount = null;
            CloudBlobContainer cloudBlobContainer = null;
            string sourceFile = null;
            string destinationFile = null;

            // Retrieve the connection string for use with the application. The storage connection string is stored
            // in an environment variable on the machine running the application called storageconnectionstring.
            // If the environment variable is created after the application is launched in a console or with Visual
            // Studio, the shell needs to be closed and reloaded to take the environment variable into account.
            string storageConnectionString = Environment.GetEnvironmentVariable("storageconnectionstring");

            // Check whether the connection string can be parsed.
            if (CloudStorageAccount.TryParse(storageConnectionString, out storageAccount))
            
                try
                
                    // Create the CloudBlobClient that represents the Blob storage endpoint for the storage account.
                    CloudBlobClient cloudBlobClient = storageAccount.CreateCloudBlobClient();

                    // Create a container called 'quickstartblobs' and append a GUID value to it to make the name unique. 
                    cloudBlobContainer = cloudBlobClient.GetContainerReference("quickstartblobs" + Guid.NewGuid().ToString());
                    await cloudBlobContainer.CreateAsync();
                    Console.WriteLine("Created container '0'", cloudBlobContainer.Name);
                    Console.WriteLine();

                    // Set the permissions so the blobs are public. 
                    BlobContainerPermissions permissions = new BlobContainerPermissions
                    
                        PublicAccess = BlobContainerPublicAccessType.Blob
                    ;
                    await cloudBlobContainer.SetPermissionsAsync(permissions);

                    // Create a file in your local MyDocuments folder to upload to a blob.
                    string localPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
                    string localFileName = "QuickStart_" + Guid.NewGuid().ToString() + ".txt";
                    sourceFile = Path.Combine(localPath, localFileName);
                    // Write text to the file.
                    File.WriteAllText(sourceFile, "Hello, World!");

                    Console.WriteLine("Temp file = 0", sourceFile);
                    Console.WriteLine("Uploading to Blob storage as blob '0'", localFileName);
                    Console.WriteLine();

                    // Get a reference to the blob address, then upload the file to the blob.
                    // Use the value of localFileName for the blob name.
                    CloudBlockBlob cloudBlockBlob = cloudBlobContainer.GetBlockBlobReference(localFileName);
                    await cloudBlockBlob.UploadFromFileAsync(sourceFile);

                    // List the blobs in the container.
                    Console.WriteLine("Listing blobs in container.");
                    BlobContinuationToken blobContinuationToken = null;
                    do
                    
                        var resultSegment = await cloudBlobContainer.ListBlobsSegmentedAsync(null, blobContinuationToken);
                        // Get the value of the continuation token returned by the listing call.
                        blobContinuationToken = resultSegment.ContinuationToken;
                        foreach (IListBlobItem item in resultSegment.Results)
                        
                            Console.WriteLine(item.Uri);
                        
                     while (blobContinuationToken != null); // Loop while the continuation token is not null.
                    Console.WriteLine();

                    // Download the blob to a local file, using the reference created earlier. 
                    // Append the string "_DOWNLOADED" before the .txt extension so that you can see both files in MyDocuments.
                    destinationFile = sourceFile.Replace(".txt", "_DOWNLOADED.txt");
                    Console.WriteLine("Downloading blob to 0", destinationFile);
                    Console.WriteLine();
                    await cloudBlockBlob.DownloadToFileAsync(destinationFile, FileMode.Create);
                
                catch (StorageException ex)
                
                    Console.WriteLine("Error returned from the service: 0", ex.Message);
                
                finally
                
                    Console.WriteLine("Press any key to delete the sample files and example container.");
                    Console.ReadLine();
                    // Clean up resources. This includes the container and the two temp files.
                    Console.WriteLine("Deleting the container and any blobs it contains");
                    if (cloudBlobContainer != null)
                    
                        await cloudBlobContainer.DeleteIfExistsAsync();
                    
                    Console.WriteLine("Deleting the local source file and local downloaded files");
                    Console.WriteLine();
                    File.Delete(sourceFile);
                    File.Delete(destinationFile);
                
            
            else
            
                Console.WriteLine(
                    "A connection string has not been defined in the system environment variables. " +
                    "Add a environment variable named 'storageconnectionstring' with your storage " +
                    "connection string as a value.");
            
        
    

【问题讨论】：

docs.microsoft.com/en-us/dotnet/api/… 应该能帮到你

【参考方案1】：

还有一些其他内置方法可以上传到 blob 存储，而无需先存储在本地驱动器中。

对于您的情况，您可以考虑以下内置方法：

1.上传流（示例见here）：

UploadFromStream / UploadFromStreamAsync

2.上传字符串/文本（示例见here）：

UploadText / UploadTextAsync

【参考方案2】：

是的，您可以使用流、字节数组、文本和文件进行上传。

UploadFromFileAsync UploadFromByteArrayAsync UploadFromStreamAsync UploadFromTextAsync

CloudBlockBlob Class

我建议您创建一个 Blob 存储库接口并使用此接口实现您的 Azure Blob 存储库类。

通过这种方式，如果您需要更改您的支持 blob 存储库，您将能够这样做，而对其余代码的影响最小。