Filter or Criteria Design Pattern - Introduction

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What is the Filter or Criteria Design Pattern?

The Filter Design Pattern (also frequently referred to as the Criteria Design Pattern) is a structural design pattern that enables developers to filter a set of objects using distinct criteria and chain them together in a decoupled, logical manner.

In software development, applications often need to filter collections based on varied, continuously changing requirements. Embedding conditional business filtering directly into services, controllers, or database queries creates tight coupling and rigid code. The Filter pattern provides an elegant way to separate filtering logic from core business entities.

Core Concepts & Participants

The structural anatomy of the Filter / Criteria pattern revolves around modular, reusable components:

• Criteria Interface: Declares a contract—typically meetCriteria(List<Item> items)—defining how a collection of objects is evaluated and filtered.
• Concrete Criteria: Individual classes that implement the criteria interface to apply specific, atomic filtering rules (e.g., filtering users by status, role, or date).
• Composite Criteria: Structural combinators like AndCriteria and OrCriteria that combine multiple criteria objects using boolean logic to evaluate complex conditions dynamically.
• Target Model / Entity: The domain objects being filtered, which remain completely decoupled from and unaware of the filtering logic.

Key Architectural Benefits

Adopting the Criteria pattern introduces major structural advantages into your codebase:

• Open/Closed Principle: You can create new criteria filters or novel logical combinations without modifying existing filters or domain objects.
• Single Responsibility Principle: Each criteria class encapsulates exactly one filtering condition, making it easy to understand and test.
• Composable Flexibility: Dynamic chains of filters can be assembled on the fly at runtime based on user inputs or system configurations.

Related Tutorials from Ram N Java

• 👉 Implementing Filter or Criteria Design Pattern in Java
• 👉 Filter or Criteria Design Pattern: Key Points
• 👉 Intercepting Filter Design Pattern Explained: Introduction and Fundamentals
• 👉 Understanding the Key Points of Intercepting Filter Design Pattern

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Filter or Criteria Design Pattern - Introduction

See also:

Filter or Criteria Design Pattern - Implementation

Filter or Criteria Design Pattern - Key Points

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