title: Intercepting filter pattern
text: # Intercepting filter pattern
  
  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 unobtrusively without changing existing code. This pattern applies reusable processing transparently before and after the actual request execution by the front and page controllers.
  
  ## 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
  
  A Filter Chain is a specific series of filters, composed so as to form a logical chain.
  
  ### 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:
  
  * Improved reusability: Common code is centralized in pluggable components enhancing reuse.
  * Increased flexibility: Generic common components can be applied and removed declaratively, improving flexibility.
  
  Reduced performance can be a concern, as unnecessarily long chains of interceptors and filters may hurt performance.
  
  ## Sample code
  
  Sample code implementation for filters with custom filter strategy is given below.
  
  Code for implementing a filter - debugging filter:
  
  Code for implementing a filter - core processor:
  
  Code for handling requests:
  
  Code for filter manager:
  
  Code for filter chain:
  
  