Explain filters and especially compression filters briefly.

A very good article explaining everything about Filters and Compression Filters is Here

Here is another link from SUN Developers Network The Essentials of Filters


How to upload files using Server-Side Programming.?

Check out Page 72(42 of 78) to learn how the Servlet API handles file uploads.
You can also find a good, free, open source file upload API is the Jakarta Commons File Upload API at page 85(55 of 78).

File Uploading using Server Side Programming