如何使用 AWS Java SDK 以 s3api 查询获取对象列表？

Question

我正在使用 AWS java SDK 进行开发。我想获得一个带有过滤器的对象列表，例如按上次修改日期过滤器。我可以在 s3api 上看到这个功能，如下所示

aws s3api list-objects 
            --bucket "myS3-BucketName" 
            --query "Contents[?LastModified>=`2018-02-01`].{Key: Key, Size: Size, LastModified: LastModified}" 
            --max-items 10"

我在 Java SDK 中找不到类似的解决方案。如何使用 Java SDK 完成这项工作？

Answer 1

使用 AWS SDK for Java 的 v2，我创建了以下实用程序方法：

/**
 * Gets S3 objects that reside in a specific bucket and whose keys conform to the 
 * specified prefix using v2 of the AWS Java SDK.
 * <br><br>
 * The objects returned will have a last-modified date between {@code start} and 
 * {@code end}.
 * <br><br>
 * Any objects that have been modified outside of the specified date-time range will 
 * not be returned.
 *
 * @param s3Client The v2 AWS S3 client used to make the request to S3.
 * @param bucket   The bucket where the S3 objects are located.
 * @param prefix   The common prefix that the keys of the S3 objects must conform to.
 * @param start    The objects returned will have been modified after this instant.
 * @param end      The objects returned will have been modified before this instant.
 * @return A {@link Stream} of {@link S3Object} objects.
 */
public static Stream<S3Object> getObjects(S3Client s3Client, String bucket, 
                                          String prefix, Instant start, 
                                          Instant end) {
    return s3Client.listObjectsV2Paginator(builder -> builder.bucket(bucket)
                   .prefix(prefix).build())
            .stream()
            .map(ListObjectsV2Response::contents)
            .flatMap(List::stream)
            .filter(s3Object -> {
                Instant lastModified = s3Object.lastModified();
                return !start.isAfter(lastModified) && !end.isBefore(lastModified);
            });
}

以下代码在逻辑上等同于您的示例：

S3Client s3Client = S3Client.create();
String bucket = "myS3-BucketName";
Instant before = Instant.parse("2018-02-01T00:00:00Z");
Instant after = Instant.MAX;

Stream<S3Object> firstTenObjects = 
    getObjects(s3Client, bucket, "", before, after).limit(10);

您可以使用以下方法从Stream中的每个S3Object中获取您要查找的数据：

• S3Object#key
• S3Object#size
• S3Object#lastModified