Spring MVC framework uses the following design patterns: 1. Singleton mode: manages the Spring container; 2. Facade mode: coordinates controller, view and model interaction; 3. Strategy mode: selects request handlers based on requests; 4. Observation Operator mode: Publish and listen to application events. These design patterns enhance the power and flexibility of Spring MVC, allowing developers to create efficient and maintainable applications.

Design patterns in the Spring MVC framework

Spring MVC is a powerful Web framework that uses a variety of design patterns to Enhance its functionality and flexibility. In this article, we will explore some of the most commonly used design patterns in Spring MVC and provide practical examples to demonstrate their application.

Singleton pattern

The singleton pattern ensures that there is only one instance of a specific class in the entire application. Spring uses the singleton pattern to manage the Spring container, which contains all Spring beans. This ensures that the Spring container is always available and the application avoids the overhead of creating multiple containers simultaneously.

Example:

@Singleton
public class SpringContainer {
    private static SpringContainer instance;

    private SpringContainer() {}

    public static SpringContainer getInstance() {
        if (instance == null) {
            instance = new SpringContainer();
        }
        return instance;
    }
}

Facade Mode

The Facade Mode provides a unified interface for accessing a set of related class or module. In Spring MVC, the DispatcherServlet class acts as a facade, coordinating the interaction between controllers, views, and models.

Example:

public class DispatcherServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 協(xié)調(diào)控制器、視圖和模型之間的交互
    }
}

Strategy Pattern

Strategy pattern allows dynamically switching classes based on algorithms or behaviors. In Spring MVC, the HandlerMapping interface provides a strategy pattern that allows applications to dynamically select which request handler to use based on the request.

Example:

public interface HandlerMapping {

    HandlerExecutionChain getHandler(HttpServletRequest req)
            throws ServletException;
}

public class SimpleUrlHandlerMapping implements HandlerMapping {

    @Override
    public HandlerExecutionChain getHandler(HttpServletRequest req)
            throws ServletException {
        // 根據(jù) URL 選擇請(qǐng)求處理程序
    }
}

Observer Pattern

The Observer pattern allows objects to subscribe to events and react to them. In Spring MVC, the ApplicationEventPublisher interface allows publishing application events, while the ApplicationListener interface allows listening to these events and reacting accordingly.

Example:

public interface ApplicationEventPublisher {

    void publishEvent(ApplicationEvent event);
}

public interface ApplicationListener<E extends ApplicationEvent> {

    void onApplicationEvent(E event);
}

// 發(fā)布事件的類(lèi)
public class MyEventPublisher {

    public void publishMyEvent() {
        ApplicationEventPublisher publisher = ... // 獲取發(fā)布者
        MyEvent event = ... // 創(chuàng)建事件
        publisher.publishEvent(event);
    }
}

// 監(jiān)聽(tīng)事件的類(lèi)
public class MyEventListener implements ApplicationListener<MyEvent> {

    @Override
    public void onApplicationEvent(MyEvent event) {
        // 處理事件
    }
}

Conclusion

The Spring MVC framework makes heavy use of design patterns to achieve its functionality and flexibility. These design patterns solve common programming problems such as class instantiation, object collaboration, and event handling. By understanding and applying these design patterns, developers can create Spring MVC applications that are maintainable, scalable, and efficient.

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