Filtering Requests with the Intercepting Filter Pattern

Some of these actions determine whether processing will continue, while others manipulate the incoming or outgoing data stream into a form suitable for further processing.
The key to solving this problem in a flexible and unobtrusive manner is to have a simple mechanism for adding and removing processing components, in which each component completes a specific filtering action.

Pre- and post-processing refer to actions taken around the core processing of a request. Certain actions dictate continuation of processing, while others modify the incoming or outgoing data stream for future processing.

The conventional approach involves a set of conditional verifications. If any of these verifications fail, the request is terminated. Although nested if/else statements are commonly used, they cause the code to become fragile and the programming style to become copy-and-paste, as the filtering flow and filter actions are hardcoded into the application. To address this issue in a versatile and non-intrusive way, a straightforward mechanism for adding and removing processing components is necessary, with each component carrying out a specific filtering action.

Illustration of Intercepting Filter Pattern using UML Diagram.

Component design

  • The filter processing is managed by
    . It creates the
    in the accurate sequence with the required filters and triggers the process.
  • The FilterChain is a sequence of distinct filters that follow a specific order.
  • FilterOne and FilterTwo refer to unique filters that are associated with a particular destination. The FilterChain is responsible for managing the order in which they are applied.
  • The requested resource by the client is referred to as the target.

An instance of the Intercepting Filter Pattern will be demonstrated.

The following codes are listed:

// Java program to illustrate


, with no repetition.

The following codes are included:






Authenticating : Downloads
Log: Downloads
Executing : Downloads

Advantages :

  • Enhanced reusability is achieved by centralizing common code into pluggable components.
  • Enhanced adaptability:
    Declarative application and removal of generic shared components can enhance the system’s adaptability.

Disadvantages :

  • Sharing of information is ineffective in detecting patterns.

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