How to set next continuation token on AWS ListObjectsV2Request object

Question

I am using AWS SDK for Java 2.15.66. I am trying to list all the objects under a particular folder. I am following code sample here https://docs.aws.amazon.com/AmazonS3/latest/userguide/ListingKeysUsingAPIs.html and had to modify since the classes in the sample are not available in my version of SDK. Following is the code I have to list objects

ListObjectsV2Request req = ListObjectsV2Request.builder()
            .bucket(S3_BUCKET_NAME)
            .prefix(pathBuilder.toString())
            .maxKeys(2)
            .build();
    ListObjectsV2Response result;
    do {
        result = s3Client.listObjectsV2(req);
        for (S3Object s3Object : result.contents()) {
            System.out.printf(" - %s (size: %d)\n", s3Object.key(), s3Object.size());
        }
        req.toBuilder().continuationToken(result.nextContinuationToken());
    } while (result.isTruncated());

This code always prints out the same two objects in each while loop. That is the nextContinuationToken() is never set. I am not able to find any other way to set the continuation token. Help appreciated.

Answer 1

Try with below code, reference link from official aws documentation

ListObjectsV2Request listObjectsReqManual = ListObjectsV2Request.builder()
            .bucket(bucketName)
            .maxKeys(1)
            .build();

    boolean done = false;
    while (!done) {
        ListObjectsV2Response listObjResponse = s3.listObjectsV2(listObjectsReqManual);
        for (S3Object content : listObjResponse.contents()) {
            System.out.println(content.key());
        }

        if (listObjResponse.nextContinuationToken() == null) {
            done = true;
        }

        listObjectsReqManual = listObjectsReqManual.toBuilder()
                .continuationToken(listObjResponse.nextContinuationToken())
                .build();
    }

You need to assign the result of .toBuilder().continuationToken(…) method to a variable