Incorrect use of ServletFileUpload (common-fileupload) results in NPE

[greglira]

We implemented a lambda function (proxy to API Gateway method which consumes multipart content) using the aws-serverless-java-container library.
However, during the testing we found out that it didn't work: all requests were failing with java.lang.NullPointerException: No FileItemFactory has been set.
It seems like the no-args constructor was used in https://github.com/awslabs/aws-serverless-java-container/blob/master/aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsProxyHttpServletRequest.java#L658
ServletFileUpload upload = new ServletFileUpload();
Javadoc of that constructior says:
Constructs an uninitialised instance of this class. A factory must be
configured, using setFileItemFactory(), before attempting
to parse requests.
However, we haven't found any setFileItemFactory() calls in the code.

So we changed line 658 to ServletFileUpload upload = new ServletFileUpload(new DiskFileItemFactory()); and it worked fine.
Can you confirm if that is a problem/bug?
Also it would be great to add a test case for this code.

Thanks,
Greg

[sapessi]

It certainly looks like a bug. I'll make the change and add some unit tests for this in the next release. Thanks!

[sapessi]

The fix for this has been merged into master. Release 0.5 will go out later today.