使用AWS Java SDK的传输管理器下载文件夹结构的解决方法如下所示：

import software.amazon.awssdk.auth.credentials.DefaultCredentialsProvider;
import software.amazon.awssdk.core.ResponseBytes;
import software.amazon.awssdk.core.sync.RequestBody;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.ListObjectsV2Request;
import software.amazon.awssdk.services.s3.model.ListObjectsV2Response;
import software.amazon.awssdk.services.s3.model.S3Object;

import java.io.File;
import java.nio.file.Paths;

public class S3FolderDownloader {

    private static final String BUCKET_NAME = "your-bucket-name";
    private static final String FOLDER_NAME = "your-folder-name";
    private static final String DESTINATION_PATH = "your-local-destination-path";

    public static void main(String[] args) {
        S3Client s3Client = S3Client.builder()
                .region(Region.US_EAST_1) // 设置正确的区域
                .credentialsProvider(DefaultCredentialsProvider.create()) // 设置正确的凭证提供者
                .build();

        ListObjectsV2Request listRequest = ListObjectsV2Request.builder()
                .bucket(BUCKET_NAME)
                .prefix(FOLDER_NAME)
                .build();

        ListObjectsV2Response listResponse = s3Client.listObjectsV2(listRequest);
        for (S3Object s3Object : listResponse.contents()) {
            String key = s3Object.key();
            String fullPath = Paths.get(DESTINATION_PATH, key).toString();

            if (!s3Object.key().endsWith("/")) { // 只下载文件，跳过文件夹
                ResponseBytes responseBytes = s3Client.getObjectAsBytes(builder -> builder.bucket(BUCKET_NAME).key(key));
                responseBytes.asByteArray(); // 这里可以对下载的字节数组进行处理，例如写入本地文件
            }

            File file = new File(fullPath);
            if (!file.exists()) {
                file.mkdirs();
            }
        }
    }
}

上述代码使用AWS Java SDK的S3Client来列出指定S3存储桶下指定前缀的所有对象。然后，通过判断对象的key是否以"/"结尾来区分文件和文件夹。只下载文件，跳过文件夹。可以根据需要对下载的字节数组进行处理，例如写入到本地文件。