ClassNotFoundException: org.apache.hadoop.fs.s3a.S3AFileSystem /code>

This means that the hadoop-aws JAR is not on the classpath.

Similarly, this error

ClassNotFoundException: com.amazonaws.services.s3.AmazonS3Client

or similar errors related to another com.amazonaws class mean that one or more of the aws-*-sdk JARs are missing.

To solve the issue, add the missing JARs to the classpath.