Core J2EE™ Patterns: Best Practices and Design Strategies

Intercepting Filter

Context

The presentation-tier request handling mechanism receives many different types of requests, which require varied types of processing. Some requests are simply forwarded to the appropriate handler component, while other requests must be modified, audited, or uncompressed before being further processed.

Problem

Preprocessing and post-processing of a client Web request and response are required.

When a request enters a Web application, it often must pass several entrance tests prior to the main processing stage. For example,

• Has the client been authenticated?

• Does the client have a valid session?

• Is the client's IP address from a trusted network?

• Does the request path violate any constraints?

• What encoding does the client ...