Question

基于https://ppolyzos.com/2016/12/30/resize-images-using-azure-functions/我有以下C＃代码来使用Azure Functions调整图像大小。

#r "Microsoft.WindowsAzure.Storage"
using ImageResizer;
using ImageResizer.ExtensionMethods;
using Microsoft.WindowsAzure.Storage.Blob;

public static void Run(Stream inputBlob, string blobname, string blobextension, CloudBlockBlob outputBlob, TraceWriter log)
{
    log.Info($"Resize function triggered\n Image name:{blobname} \n Size: {inputBlob.Length} Bytes");
    log.Info("Processing 520x245");

    /// Defining parameters for the Resizer plugin
    var instructions = new Instructions
    {
        Width = 520,
        Height = 245,
        Mode = FitMode.Carve,
        Scale = ScaleMode.Both
    };

    /// Resizing IMG
    Stream stream = new MemoryStream();
    ImageBuilder.Current.Build(new ImageJob(inputBlob, stream, instructions));
    stream.Seek(0, SeekOrigin.Begin);

    /// Changing the ContentType (MIME) for the resulting images
    string contentType = $"image/{blobextension}";
    outputBlob.Properties.ContentType = contentType;
    outputBlob.UploadFromStream(stream);
}

结果将是名为520x245-{blobname}.{blobextension}的图像。

我希望只有在blob容器中不存在生成的图像时才能运行代码如何获取容器上的现有文件？

Answer 1

由于您使用CloudBlockBlob类型绑定outputBlob。您可以使用以下代码检查此blob是否存在。

if (outputBlob.Exists())
{
    log.Info($"520x245-{blobname}.{blobextension} is already exist");  
}
else
{
    log.Info($"520x245-{blobname}.{blobextension} is not exist");  
    //do the resize and upload the resized image to blob  
}

目前，Azure功能并不允许我们在输出blob绑定中使用CloudBlockBlob。解决方法是将方向更改为＆＃34; inout＆＃34;在function.json中。之后，我们可以在输出blob绑定中使用CloudBlockBlob。

{
  "type": "blob",
  "name": "outputBlob",
  "path": "mycontainer/520x245-{blobname}.{blobextension}",
  "connection": "connectionname",
  "direction": "inout"
}

Answer 2

检查Blob是否存在于容器中，但是您还需要添加CloudBlobContainer作为输入参数。

CloudBlockBlob existingBlob = container.GetBlockBlobReference(blobName);

使用

检查是否存在

await existingBlob.ExistsAsync()

Answer 3

借助Azure Blob存储库v12，您可以使用BlobBaseClient.Exists()/BlobBaseClient.ExistsAsync()

用法如下所示，

var blobServiceClient = new BlobServiceClient(_storageConnection);
BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(_containerName);
BlobClient blobClient = containerClient.GetBlobClient(blobName);

bool isExists = await blobClient.ExistsAsync(cancellationToken);

BlobBaseClient.Exists(CancellationToken) Method

BlobBaseClient.ExistsAsync(CancellationToken) Method

Answer 4

相同的Java版本（使用新的v12 SDK）

这使用共享密钥凭据授权，即帐户访问密钥。

StorageSharedKeyCredential credential = new StorageSharedKeyCredential(accountName, accountKey);
String endpoint = String.format(Locale.ROOT, "https://%s.blob.core.windows.net", accountName);
BlobServiceClient storageClient = new BlobServiceClientBuilder().credential(credential)
                                      .endpoint(endpoint).buildClient();

BlobContainerClient container = storageClient.getBlobContainerClient(containerName)
if ( container.exists() ) {
   // perform operation when container exists 
}

使用Azure功能检查Blob存储上是否存在文件

4 个答案: