How Can the Strategy Pattern Enhance File Encryption Based on File Size?

Strategy Pattern in a Real-World Context: File Encryption

The Open-Closed Principle (OCP) advocates for designing code that is open to extension but closed to modification. One way to achieve this is by employing the Strategy Pattern. While the concept of applying it to different validation classes is valid, there are further practical examples where the strategy pattern shines.

Consider the scenario of encrypting a file. The choice of encryption strategy depends on the file size. For small files, an "in-memory" strategy where the entire file is held in memory may suffice. However, for larger files, a different strategy utilizing partial memory loading and temporary file storage for encrypted results is optimal.

In this context, the Strategy Pattern allows for multiple encryption strategies, each implementing the same interface. The client code remains unaware of the specific strategy used, simplifying the decision-making process within the CipherFactory.

interface Cipher {
     public void performAction();
}

class InMemoryCipherStrategy implements Cipher { 
         public void performAction() {
             // in-memory encryption logic
         }
}

class SwaptToDiskCipher implements Cipher { 
         public void performAction() {
             // partial memory and temporary file encryption logic
         }
}

// client code
File file = getFile();
Cipher c = CipherFactory.getCipher(file.size());
c.performAction();

The CipherFactory determines the appropriate strategy based on the file size and returns an instance to the client code. This design allows for seamless integration of new encryption strategies without modifying the client code, adhering to the principles of OCP. The result is a flexible and extensible encryption system that can handle files of varying sizes efficiently.

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