What are the categories of design pattern applications in the Java framework?

In the Java framework, design patterns are applied by category, including: Creational design patterns: Singleton pattern, Factory method pattern, Builder pattern Structural design patterns: Adapter pattern, Decorator pattern, Agent pattern Behavioral design pattern : Observer pattern, strategy pattern, template method pattern practical cases include singleton pattern in Spring, strategy pattern in Struts 2 and proxy pattern in Hibernate ORM.

Categories of design pattern applications in the Java framework

Design patterns are reusable solutions used to solve software design problems Common challenges. In Java frameworks, design patterns are widely used to improve the scalability, maintainability, and flexibility of the framework.

Categories of design patterns in the Java framework:

Creative design pattern:

• Single case pattern : Ensure that at most one instance of the class exists.
• Factory method pattern: Create an interface for an object without specifying a specific implementation of the class.
• Builder pattern: Separates the complex creation process of objects, making it easier to control and extend.

Structural design pattern:

• Adapter pattern: Adapt one class to another class so that they can work together.
• Decorator pattern: Dynamically add functionality to objects.
• Proxy pattern: Provide a proxy or replacement object for another object.

Behavioral design pattern:

• Observer pattern: When the state of an object changes, other objects are allowed to be notified.
• Strategy pattern: allows users to encapsulate algorithms or behaviors into different classes.
• Template method pattern: Defines the skeleton of an algorithm, allowing subclasses to redefine certain steps.

Practical case:

Singleton pattern in Spring Framework:

Spring Framework uses singleton pattern To manage Bean instances. With the @Singleton annotation, you can specify that a Bean should be created as a singleton, meaning that it will be instantiated only once.

@Service
@Singleton
public class MyService {
    // ...
}

Strategy Pattern in Struts 2:

Struts 2 uses the Strategy pattern to manage validation logic. You can define different validator classes and associate them with Struts 2 operations using the @Validator annotation.

@Validator
public class MyValidator implements Validator {
    // ...
}

Proxy pattern in Hibernate ORM:

Hibernate uses proxy pattern to manage entity objects. A proxy object behaves like an actual entity object, but allows Hibernate to intercept calls to the entity object and perform certain operations, such as loading data or maintaining state.

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