Delegate pattern

The delegate pattern is responsible for the invocation and assignment of tasks

The DispatcherServlet in Spring MVC uses the delegate pattern

The strategy pattern

Application scenarios

  1. There are many classes in the system, and they differ only in their behavior

  2. A system needs to dynamically choose one of several algorithms (business scenario of choosing payment method)

Policy patterns are implemented through container singleton patterns and factory patterns

In the JDK, the commonly used compare method is a policy schema

Template pattern

Implement the invariant parts of an algorithm once and leave the mutable behavior to subclasses

Extract common behavior to avoid code duplication

JDBC operations

Adapter mode

Reconstruct the service scenario for free third-party login

Decorator pattern

Attach functionality to an object without changing the original object

Similar to static proxies, but instead of enhancing methods, it adds functionality to objects

Observer model

Also known as publish and subscribe