Intercepting Filter is a JavaEE pattern which creates pluggable filters to process common services in a standard manner without requiring changes to core request processing code. The filters intercept incoming requests and outgoing responses, allowing preprocessing and post-processing, and these filters can be added or removed unobstrusively without changing existing code. This pattern applies reusable processing transparently before and after the actual request execution by the front and page controllers.
Contents
Structure
Filter manager, filter chain, filters and target are components of the pattern.
Filter manager
This manages filter processing and creates the filter chain with the appropriate filters, in the correct order, and initiates processing.
Filter chain
This is an ordered collection of independent filters.
Filters
These are the individual filters that are mapped to a target and their processing is coordinated by filter chain.
Target
This is the resource requested by the client.
Consequences
Following benefits can be considered:
Reduced performance can be concerned as unnecessarily long chains of interceptors and filters may hurt performance.
Sample code
Sample code implementation for filters with custome filter strategy is given below.
Code for implementing a filter - debgging filter:
Code for implementing a filter - core processor:
Code for handling requests:
Code for filter manager:
Code for filter chain: