根据通配符确定S3存储桶中是否存在对象

Question

有人可以告诉我如何确定S3存储桶中是否存在某个文件/对象,并显示消息是否存在或是否存在.

基本上我想要它:

1)检查我的S3帐户上的一个桶,例如testbucket

2)在该存储桶内部,查看是否存在前缀为test_(test_file.txt或test_data.txt)的文件.

3)如果该文件存在,则显示该文件存在的MessageBox(或控制台消息),或该文件不存在.

有人可以告诉我该怎么做吗？

Answer 1

使用S3FileInfo.Exists方法:

using (var client = Amazon.AWSClientFactory.CreateAmazonS3Client(accessKey, secretKey))
{
    S3FileInfo s3FileInfo = new Amazon.S3.IO.S3FileInfo(client, "your-bucket-name", "your-file-name");
    if (s3FileInfo.Exists)
    {
         // file exists
    }
    else
    {
        // file does not exist
    }   
}

Answer 2

使用AWSSDK For .Net I目前做的事情如下:

public bool Exists(string fileKey, string bucketName)
{
        try
        {
            response = _s3Client.GetObjectMetadata(new GetObjectMetadataRequest()
               .WithBucketName(bucketName)
               .WithKey(key));

            return true;
        }

        catch (Amazon.S3.AmazonS3Exception ex)
        {
            if (ex.StatusCode == System.Net.HttpStatusCode.NotFound)
                return false;

            //status wasn't not found, so throw the exception
            throw;
        }
}

它有点糟糕,但它现在有效.

Answer 3

这解决了它:

列出现有对象的存储桶,并使用这样的前缀.

    var request = new ListObjectsRequest()
        .WithBucketName(_bucketName)
        .WithPrefix(keyPrefix);

    var response = _amazonS3Client.ListObjects(request);

    var exists = response.S3Objects.Count > 0;

    foreach (var obj in response.S3Objects) {
        // act
    }

Answer 4

我知道这个问题已经有几年了,但是新的SDK处理得很漂亮.如果有人还在搜索这个.您正在寻找S3DirectoryInfo类

using (IAmazonS3 s3Client = new AmazonS3Client(accessKey, secretKey))
{
    S3DirectoryInfo s3DirectoryInfo = new Amazon.S3.IO.S3DirectoryInfo(s3Client, "testbucket");
    if (s3DirectoryInfo.GetFiles("test*").Any())
    {
        //file exists -- do something
    }
    else
    {
        //file doesn't exist -- do something else
    }
}

Answer 5

不确定这是否适用于 .NET Framework，但 AWS SDK (v3) 的 .NET Core 版本仅支持异步请求，因此我不得不使用稍微不同的解决方案：

/// <summary>
/// Determines whether a file exists within the specified bucket
/// </summary>
/// <param name="bucket">The name of the bucket to search</param>
/// <param name="filePrefix">Match files that begin with this prefix</param>
/// <returns>True if the file exists</returns>
public async Task<bool> FileExists(string bucket, string filePrefix)
{
    // Set this to your S3 region (of course)
    var region = Amazon.RegionEndpoint.USEast1;

    using (var client = new AmazonS3Client(region))
    {
        var request = new ListObjectsRequest {
            BucketName = bucket,
            Prefix = filePrefix,
            MaxKeys = 1
        };

        var response = await client.ListObjectsAsync(request, CancellationToken.None);

        return response.S3Objects.Any();
    }
}

而且，如果要搜索文件夹：

/// <summary>
/// Determines whether a file exists within the specified folder
/// </summary>
/// <param name="bucket">The name of the bucket to search</param>
/// <param name="folder">The name of the folder to search</param>
/// <param name="filePrefix">Match files that begin with this prefix</param>
/// <returns>True if the file exists</returns>
public async Task<bool> FileExists(string bucket, string folder, string filePrefix)
{
    return await FileExists(bucket, $"{folder}/{filePrefix}");
}

用法：

var testExists = await FileExists("testBucket", "test_");
// or...
var testExistsInFolder = await FileExists("testBucket", "testFolder/testSubFolder", "test_");