Detailed explanation of the technical principles and usage of the "Phantom" framework in the Java library

The Shadow framework is a lightweight framework used in the Java library for dynamic proxy.It uses Java's reflection mechanism and dynamic proxy technology, which can dynamically generate proxy objects at runtime and add additional logic to the agent object.In this article, we will introduce the technical principles and usage methods of the phantom framework in detail, and provide some Java code examples. 1. Technical principle: 1. Reflective mechanism: Java provides a set of APIs that can obtain category information at runtime, and can dynamically operate class and objects.The reflection mechanism allows us to dynamically load, detect and use classes through the name of the class, including calling class methods, accessing and modifying attributes, etc. 2. Dynamic proxy: Dynamic proxy is a design pattern that allows creating an agent object that implements a set of given sets during runtime.The proxy object can intercept access to the target object and perform some additional logic before and after the method of the target object. 3. Phantom frame structure: The phantom frame is composed of two major components, which are agent factories and interceptors.The proxy factory is responsible for creating an agent object, and the interceptor is responsible for adding additional logic to the proxy object.When the method of the proxy object is called, the interceptor will intercept calls and execute custom logic. 2. How to use: 1. Introduce the phantom framework: First of all, you need to introduce the dependence of the phantom framework in the project. You can achieve it by adding the jar file of the framework to the project path. 2. Create interface: Define a interface, which is the type of target object that needs to be agent. 3. Implement the target object: Create a class that achieves the target interface, which is the specific business logic implementation. 4. Implementation interceptor: Create a class and implement the Interceptor interface, which will carry additional logic.In the Internet method, you can add custom logic before and after the target method execution. 5. Create proxy objects: By calling the CreateProxy method of the proxy factory, the target interface and interceptor can be transmitted to the proxy object. The following is a simple example: Define an interface: public interface UserService { void saveUser(String name); void deleteUser(String name); } Implement target object: public class UserServiceImpl implements UserService { public void saveUser(String name) { System.out.println("Saving user: " + name); } public void deleteUser(String name) { System.out.println("Deleting user: " + name); } } Implementation interceptor: public class LoggingInterceptor implements Interceptor { public Object intercept(Invocation invocation) throws Exception { System.out.println("Before method execution"); Object result = invocation.proceed (); // Call the target method System.out.println("After method execution"); return result; } } Create an agent object: public class Main { public static void main(String[] args) { UserService userService = ProxyFactory.createProxy(UserService.class, new LoggingInterceptor()); userService.saveUser("John"); userService.deleteUser("John"); } } Run this example, the output result is: Before method execution Saving user: John After method execution Before method execution Deleting user: John After method execution It can be seen that when calling the proxy object method, the interceptor will output the corresponding information before and after the execution of the target method. Summarize: The Shadow framework uses the Java's reflection mechanism and dynamic proxy technology, providing a simple and flexible way to realize the acting object of dynamic adding logical.By defining interfaces, realizing target objects, writing interceptors, and creating agency objects, we can flexibly add additional logic to the code to achieve a higher -level programming mode.