file-upload sample allows to upload a file and writes it to /tmp
directory as:

for (Part part : request.getParts()) {
fileName = part.getSubmittedFileName();
part.write(fileName);
}

part.write() is not throwing any exception but not even writing the file.

Complete sample is at:

https://github.com/arun-gupta/javaee7-samples/tree/master/servlet/file-upload