Filter

• A filter dynamically intercepts requests and responses to transform or use the information contained in the requests or responses but typically do not themselves create responses.
• Filters improve reusability by placing recurring tasks in the filter as a reusable unit.
• The filters can be used for
• caching and compressing content,
• logging and auditing,
• image conversions (scaling up or down etc),
• authenticating incoming requests,
• XSL transformation of XML content,
• localization of the request and the response,
• site hit count etc.
• The filters are configured through the web.xml file as follows:

HitCounterFilter myPkg.HitCounterFilter HitCounterFilter /usersection/* ...

• Servlet filters use the slightly modified version of the chain of responsibility design pattern.