Proxy pattern AOP in Spring Framework

In the Spring framework, AOP (Aspect Oriented Programming) is an important design pattern. It realizes modular development by separating Cross-cutting concern (such as logging, transaction management, etc.) from business logic modules. The core idea of AOP is to weave additional logic before and after the method execution of the target object through the Proxy pattern, so as to realize the function of Cross-cutting concern. In the Spring framework, the implementation of AOP mainly utilizes dynamic proxies. When we use Spring AOP, the framework helps us automatically create a proxy object to add additional logic before and after the method execution of the target object. Spring provides two implementations of AOP: interface based proxies and class based proxies. The interface based proxy is implemented using JDK's dynamic proxy. In this proxy method, the proxy object implements the interface of the target object, and when calling the proxy object's methods, it actually calls the InvocationHandler's invoke method through a reflection mechanism. In the invoke method, we can add additional logic to complete the function of Cross-cutting concern. The following is an example of the implementation code of the interface based Proxy pattern AOP in the Spring framework: import org.aopalliance.intercept.MethodInterceptor; import org.aopalliance.intercept.MethodInvocation; public class LoggingInterceptor implements MethodInterceptor { @Override public Object invoke(MethodInvocation invocation) throws Throwable { //Logic before executing the target method System.out.println("Before method: " + invocation.getMethod().getName()); //Calling the target method Object result = invocation.proceed(); //Logic after executing the target method System.out.println("After method: " + invocation.getMethod().getName()); return result; } } Class based proxies use CGLIB to generate proxy classes. In this proxy mode, the proxy object inherits the class of the target object and rewrites the method of the target object. Additional logic can be added in the method to realize the function of Cross-cutting concern. The following is an example of the implementation code of the class based Proxy pattern AOP in the Spring framework: import org.springframework.cglib.proxy.MethodInterceptor; import org.springframework.cglib.proxy.MethodProxy; public class LoggingInterceptor implements MethodInterceptor { @Override public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { //Logic before executing the target method System.out.println("Before method: " + method.getName()); //Calling the target method Object result = proxy.invokeSuper(obj, args); //Logic after executing the target method System.out.println("After method: " + method.getName()); return result; } } Summary: AOP in the Spring framework is implemented through the Proxy pattern, weaving additional logic before and after the method execution of the target object, so as to realize the function of Cross-cutting concern. AOP can help us achieve Cross-cutting concern such as logging, transaction management, security verification, and improve the Reusability and maintainability of the code.