There's no sense in reinventing the wheel--here are some servlet support classes I wrote that you can use. Most famous is the file upload package MultipartRequest and MultipartParser. Please read the license before use.

View the Readme
View the License
View the FAQ

View class documentation

Class Index

• class Base64Decoder
• class Base64Encoder
• class CacheHttpServlet
• class DaemonHttpServlet
• class RemoteDaemonHttpServlet (implements java.rmi.Remote)
• class RemoteHttpServlet (implements java.rmi.Remote)
• class HttpMessage
• class HttpsMessage
• class LocaleNegotiator
• class LocaleToCharsetMap
• class MailMessage
• class MultipartRequest
• class MultipartParser
• class FilePart
• class ParamPart
• class FileRenamePolicy (New)
• class DefaultFileRenamePolicy (New)
• class MultipartFilter
• class MultipartWrapper
• class MultipartResponse
• class ParameterParser
• class ServletUtils
• class VersionDetector

• class ParameterNotFoundException

This is a .zip readable by "jar", newer releases are at the top. To be notified when new versions release, subscribe here. Be sure to check out the FAQ and Javadocs below.
Version	Comments
cos-05Nov2002.zip	Many file upload improvements: Resolved an issue where exceptions were thrown if a boundary hit just at the end of the 64k read buffer. Enhanced MultipartRequest to include query string parameters in its parameter list. Added a MultipartParser constructor that takes a character encoding. Added support to MultipartParser for browsers that send a preamble. Added support for unquoted header values (helpful to lynx browsers). Added support for file names as part of the Content-Type header (helpful to Opera browsers). Made DefaultFileRenamePolicy thread-safe. Also added a new variety of encode/decode methods to the Base64Encoder/Decoder classes. Improved MailMessage's handling of CC address headers. Enhanced the documentation in several places, and added several entries to the FAQ.
cos-27May2002.zip	Polished the file renaming logic a little. A getFilesystemName() call now returns the renamed filename, and a new method getOriginalFileName() returns the original name.
cos-09May2002.zip	Added i18n abilities to the file upload classes. There's now support for non-Latin-1 filenames and parameter values. See the new MultipartRequest constructors and MultipartParser setter methods. Added pluggable file renaming logic to avoid collisions when files of the same name are uploaded concurrently. See the new FileRenamePolicy class and the new MultipartRequest setter methods. Added a bug fix for file uploads coming from Opera browsers, where header values may be split across lines. No public API change, only better behavior.
cos-19Jun2001.zip	Added MultipartFilter and MultipartWrapper, to allow semi-automatic file uploads using the new Servlet API 2.3 filter mechanism.