~/Common Issues with Design Patterns in Real World Applications

Feb 13, 2019

Design patterns offer architectural solutions based on experience, but their use in software development presents several recurring issues. This article outlines the primary challenges encountered with design patterns in real world settings and provides links for further detail.

Overuse and Pattern Obsession

A frequent problem is overuse of established patterns. Developers may apply patterns unnecessarily, leading to complexity and reduced code clarity. This is sometimes called patternitis.

Misapplication and Context Ignorance

Misapplying a pattern without considering project requirements can create rigid architectures. Patterns must be adapted to context, not used as rigid templates: see contextual adaptation discussion.

Increased Code Complexity

By introducing extra layers, some patterns like Decorator or Abstract Factory, can make code harder to trace and debug. This leads to understandability issues for teams.

Learning Curve and Onboarding

Patterns such as Visitor or Proxy add concepts new team members must master, impacting onboarding time. Teams must invest in training and documentation.

Performance Overheads

Some patterns, especially those introducing indirection, can reduce performance. For example, the Decorator may add multiple object wrappers.

Tooling and Framework Constraints

Frameworks or libraries may already implement similar patterns or restrict custom implementations, creating redundancy or conflicts. For example, dependency injection is supported by frameworks like Spring.

Parallelism and Patterns

Many classic patterns do not address concurrency, making them risky in multi-threaded environments. For instance, Singleton may be unsafe without extra synchronization.

Documentation and Communication

Patterns are based on common vocabulary, but team members may not share the same understanding or may use patterns in nonstandard ways, as discussed in the Pattern-Oriented Software Architecture guide.

Legacy System Integration

Introducing patterns into legacy systems can be challenging if existing structure mismatches pattern requirements, demanding costly refactoring. Learn more at Refactoring Guru.

Hidden Coupling

Some implementations, such as Observer, may introduce hidden dependencies, making it difficult to track event flows and dependencies between modules.

Code Example: Overuse of Singleton

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public class DatabaseConnection {
    private static DatabaseConnection instance;
    private DatabaseConnection() {}
    public static DatabaseConnection getInstance() {
        if (instance == null) {
            instance = new DatabaseConnection();
        }
        return instance;
    }
}

The Singleton pattern is easy to overuse and creates hidden global state, potentially harming testability.

Conclusion

Design patterns remain valuable, but applying them with critical evaluation of context, performance, and codebase needs is essential for maintainable software. Over-reliance or incorrect application leads to many difficulties outlined above.