What is the principle of dynamic proxy in AOP?

The principle of dynamic proxy in Aspect-Oriented Programming (AOP) is to create a proxy object to replace the original object in executing the target method and inserting additional logic (aspect) before and after the target method, thereby enhancing the target method.

The specific implementation principle is as follows:

1. Define an aspect that contains the logic that needs to be enhanced.
2. Create a proxy object that implements the same interface as the original object, while also holding a reference to the original object.
3. When calling methods in the proxy object, the proxy object will insert aspect logic before and after the target method is executed.
4. The proxy object determines whether to insert aspects before or after the target method based on configuration files or annotations.
5. If the logic of inserting an aspect is needed, the before advice of the aspect will be called before the target method execution, and the after advice of the aspect will be called after the target method execution.
6. Aspects can be defined with multiple types of advice, such as before advice, after advice, returning advice, exception advice, etc., and can be configured as needed.
7. The proxy object combines the logic of the aspect with the target method logic of the original object, creating an enhanced target method.