Question

I quote from Apache Commons Page for Commons FileUpload

This page describes the traditional API of the commons fileupload
library. The traditional API is a convenient approach. However, for
ultimate performance, you might prefer the faster Streaming API.

My Question

What specific differences make Streaming API faster than traditional API?

Answer 1

The key difference is in the way you’re handling the file, as you noticed by yourself with the factory class.

The streaming API is not saving in disk while getting the input stream. In the end, you’ll be able to handle the file faster (with a cost on temporary memory)… but the idea is to avoid saving the binary in disk unless you really want/need to.

After that, you are able to save the data to disk, of course, using a bufferedinputstream, a byte array or similar.

EDIT: The handler when you open the stream ( fileItemStreamElement.openStream() ) is a common InputStream instance. So, the answer to your “what if it’s a big file” is something like this Memory issues with InputStream in Java

EDIT: The streaming API should not save to disk OR save in memory. It simply provides a stream you can read from to copy the file to where ever you want. This is a way to avoid having a temp directory and also avoid allocating enough memory to hold the file. This should be faster at least because it is not copied twice, once from the browser to disk/memory and then again from disk/memory to where ever you save it.