What is the implementation principle of JDK dynamic proxy?

JDK dynamic proxy is implemented through the reflection mechanism, utilizing Java’s reflection API to dynamically create proxy classes and objects at runtime.

The specific implementation steps are as follows:

1. Define an interface that needs to be proxied.
2. Implement an InvocationHandler interface, which contains an invoke method for handling method calls of the proxy object.
3. In the invoke method, the method name, parameters, and other information are obtained through reflection, and some preprocess or postprocess is performed as needed.
4. Create a proxy object by using the newProxyInstance method of the Proxy class, passing in a class loader, the interface to be proxied, and an instance of InvocationHandler.
5. When calling a method on a proxy object, what is actually being called is the invoke method of the InvocationHandler, which will execute the corresponding logic or call the corresponding method of the proxied object based on the method name and other information.

In summary, JDK dynamic proxy dynamically creates proxy classes and objects at runtime, delegates method calls to an InvocationHandler for processing, thereby intercepting and enhancing method calls to the proxied object.