Factory

Enhanced Definition

In the context of mainframe application development, particularly for object-oriented languages like Java or C++ running on z/OS, a Factory is a design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created. It encapsulates the object creation logic, decoupling the client code from the concrete classes it instantiates.

Key Characteristics

- Decoupling: Separates the responsibility of creating objects from the code that uses them, enhancing modularity and reducing dependencies.
- Encapsulation of Creation Logic: All logic related to object instantiation (e.g., determining which concrete class to create based on parameters, configuring the object) is centralized within the factory.
- Flexibility and Extensibility: Allows new product types to be introduced without modifying the client code, simply by extending the factory or adding new concrete product classes.
- Polymorphic Creation: Often returns objects that conform to a common interface or abstract class, enabling client code to work with different concrete implementations interchangeably.
- Resource Management: Can be used to manage the lifecycle of complex objects, including pooling or caching, which is critical for performance in high-volume z/OS environments.

Use Cases

- Database Connection Management: A factory can provide different DB2 or IMS connection objects based on configuration parameters (e.g., test vs. production environment, specific database instance), abstracting the underlying data source.
- Report Generation: In a Java application on z/OS, a factory might create different types of report generators (e.g., for CSV, XML, or PDF output) based on user preferences or batch job parameters.
- Service Implementation Selection: For CICS or IMS transaction processing where different business logic implementations are required based on input data, a factory can dynamically instantiate the appropriate service object.
- Resource Pooling: A factory can manage a pool of reusable objects, such as MQ message producers or specialized data processors, to optimize performance and reduce overhead in critical batch or online systems.

Related Concepts

The Factory pattern is a fundamental Object-Oriented Programming (OOP) concept, heavily utilized in Java on z/OS and C++ on z/OS applications. It is closely related to other design patterns like Abstract Factory and Factory Method. It supports principles like polymorphism and encapsulation. In enterprise mainframe environments, factories are often found within applications deployed on WebSphere Application Server for z/OS or integrated with CICS Transaction Server and DB2 for z/OS to manage complex object lifecycles and resource access.

Best Practices:

Define Clear Interfaces: Ensure that the products created by the factory adhere to well-defined interfaces or abstract classes, promoting loose coupling.
Keep Factories Focused: A factory should ideally have a single responsibility: creating objects. Avoid adding unrelated business logic to the factory itself.
Handle Creation Errors Gracefully: Implement robust error handling within the factory to manage scenarios where object instantiation fails, which is crucial for the reliability of z/OS applications.
Consider Dependency Injection: For complex applications, integrate factories with dependency injection frameworks (e.g., Spring on z/OS) to manage factory instances and their dependencies, simplifying configuration and testing.
Document Factory Logic: Clearly document the types of objects a factory can create, the parameters it accepts, and any specific configuration required, aiding maintainability for mainframe developers.