Web programming

Units WEB1P and WEB2P

Filters

The Java Servlet specification version 2.3 introduced a new component type, called a filter. A filter dynamically intercepts requests and responses to transform or use the information contained in the requests or responses. Filters typically do not themselves create responses, but instead provide universal functions that can be "attached" to any type of servlet or JSP page.

Filters can perform many different types of functions, including

Authentication-Blocking requests based on user identity.
Logging and auditing-Tracking users of a web application.
Image conversion-Scaling maps, and so on.
Data compression-Making downloads smaller.
Localization-Targeting the request and response to a particular locale.
XSL/T transformations of XML content-Targeting web application responses to more that one type of client.
Encryption
Tokenizing
Triggering resource access events
Mime-type chaining
Caching

See The Essentials of Filters for more details.

The API for the Filter interfaces is in the Java Servlet API.

	Last updated by Prof Jim Briggs of the School of Computing at the University of Portsmouth
	The web programming units include some material that was formerly part of the WPRMP, WECPP, WPSSM and WEMAM units.