This appendix is based on the Public Review Draft of the Servlet 2.3 Specification. That specification was scheduled for final release after this book went to press; therefore, some details in this appendix may change by the time you read this. The code for this appendix was tested with Resin1.3; see for information about Resin.

Servlet filters, introduced in the Servlet 2.3 specification, address one of the biggest drawbacks of servlets and JSP: the inability to filter servlet output. This restriction hinders the development of many features that benefit from filtering requests, such as logging, authentication, XSLT processing, etc.

Before the Servlet 2.3 specification, the only portable way to approximate ...

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