亚马逊S3列出"目录"

Question

我已经通过AWS S3管理控制台在S3中创建了一个层次结构.如果我运行以下代码来列出存储桶:

AmazonS3 s3 = new AmazonS3Client(CRED);
ListObjectsRequest lor = new ListObjectsRequest()
                             .withBucketName("myBucket")
                             .withPrefix("code/");
ObjectListing objectListing = s3.listObjects(lor);
for (S3ObjectSummary summary: objectListing.getObjectSummaries()) {
    System.out.println(summary.getKey());
}

我明白了:

code/ 
code/03000000-0001-0000-0000-000000000000/ 
code/03000000-0001-0000-0000-000000000000/special.js 
code/03000000-0001-0000-0000-000000000000/test.js 
code/03000000-0002-0000-0000-000000000000/ 

这正是我所期待的.如果我添加一个分隔符,所以我只在"代码/"下直接列出内容,现在我没有得到任何子目录.

更改上面的行(在末尾添加withDelimiter()):

ListObjectsRequest lor = new ListObjectsRequest().withBucketName("myBucket")
                                                 .withPrefix("code/")
                                                 .withDelimiter("/");

我现在只得到:

code/ 

我知道S3没有"目录",而是分隔键,但这种行为看起来很奇怪？我如何列出"代码"下面的内容？

Answer 1

如果您拥有没有内容的密钥,S3会将其视为"通用前缀":

http://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/model/ObjectListing.html#getCommonPrefixes%28%29

public List getCommonPrefixes()

获取此对象列表中包含的公共前缀.只有在原始请求中指定了分隔符时,才会出现公共前缀.

每个公共前缀表示S3存储桶中的一组密钥,这些密钥已从对象汇总结果中压缩并省略.这允许应用程序按层次组织和浏览其密钥,类似于文件系统将文件组织到目录中的方式.

例如,考虑包含以下键的存储桶:

"foo/bar/baz"
"foo/bar/bash"
"foo/bar/bang"
"foo/boo"

如果在此存储桶上调用前缀="foo /"和delimiter ="/"的listObjects,则返回的S3ObjectListing将在公共前缀列表("foo/bar /")中包含一个条目,并且没有任何以该条目开头的键公共前缀将包含在对象摘要列表中.

返回:此对象列表中包含的公共前缀列表,如果未找到公共前缀,则可能是空列表.

Answer 2

This below code worked for me to list all directories in s3.

private static String bucket_name = "";
private static String secret_key = "";
private static String access_key = "";
private static String Regions region = Regions.SELECT_REGION;

public static void main(String[] args) {
        System.out.println(listKeysInBucket(bucket_name, "/"));
    }

    public static List<String> listKeysInBucket(String bucketName, String prefix) {
        boolean isTopLevel = false;
        String delimiter = "/";
        if (prefix.equals("") || prefix.equals(delimiter)) {
            isTopLevel = true;
        }
        if (!prefix.endsWith(delimiter)) {
            prefix += delimiter;
        }

        ListObjectsRequest listObjectsRequest = null;
        if (isTopLevel) {
            listObjectsRequest = new ListObjectsRequest().withBucketName(bucketName).withDelimiter(delimiter);
        } else {
            listObjectsRequest = new ListObjectsRequest().withBucketName(bucketName).withPrefix(prefix)
                    .withDelimiter(delimiter);
        }

        ObjectListing objects = s3Client().listObjects(listObjectsRequest);
        return objects.getCommonPrefixes();
    }

    public static AmazonS3 s3Client() {
        AWSCredentials s3Configs = new BasicAWSCredentials(access_key,secret_key);
        return AmazonS3ClientBuilder.standard()
                .withCredentials(new AWSStaticCredentialsProvider(s3Configs)).withRegion(region )
                .build();
    }