Introduction to the technical principles of the Aop Utilities framework in the Java library
AOP (facing surface programming) is a programming paradigm that allows developers to cut and concentrate on the focus without changing the existing code to achieve the modularization of cross -section attention points.The Aop Utilities framework in the Java class library provides a set of tools and classes to support AOP in Java applications.
The technical principle of the AOP Utilities framework is based on the Java reflection mechanism and dynamic agent.It uses a dynamic proxy object to achieve the proxy of the target object by generating a dynamic proxy object, thereby intercepting and enhancing the target object.The following is the main technical principle of the AOP Utilities framework:
1. Dynamic proxy: The AOP Utilities framework uses Java's dynamic proxy mechanism to create the proxy of the target object.By dynamic proxy, Aop Utilities can intercept the method of the target object to in order to inject customized processing logic before and after the method execution.
2. Cut point expression: The AOP Utilities framework uses the cut point expression to determine what method calls should be applied to the cutting logic.Cut point expression is a powerful language with a description method to call the matching rules.It can select the method according to the method name, parameter type, return type and other conditions.
3. Notification: The notification of the AOP Utilities framework is a code block triggered before, after the execution, and occurrence of abnormalities.They are defined in the logic of cutting to achieve additional functions related to target objects, such as log records and transaction management.
4. Cut surface: Aop Utilities framework combines different notifications into cut surfaces.The cut surface represents a set of notifications and a combination of a cut point expression. It defines which notifications are applied in which method calls are applied.By applying the cut surface to the target object, the AOP Utilities framework can intercept and modify the target object during the method call.
Below is a simple example. Use the AOP Utilities framework to implement the log record function:
import com.abc.aop.aspectj.LoggingAspect;
import com.abc.aop.aspectj.AspectUtils;
public class Main {
public static void main(String[] args) {
// Create the target object
MyService myService = new MyService();
// Create cutting objects
LoggingAspect loggingAspect = new LoggingAspect();
// Apply the cut surface to the target object
MyService proxy = AspectUtils.createProxy(myService, loggingAspect);
// The method of calling the proxy object
proxy.doSomething();
}
}
public class MyService {
public void doSomething() {
System.out.println("Doing something...");
}
}
public class LoggingAspect {
public void beforeAdvice() {
System.out.println("Before method execution");
}
public void afterAdvice() {
System.out.println("After method execution");
}
public void afterThrowingAdvice() {
System.out.println("Exception occurred");
}
}
In the above example, we first created a target object, myService`.Then, we created a cut object, which contains the three notification methods of `BeForeAdvice`,` AFTERADVICE` and `AFTERTHROWINGVICE.Next, we use the ASPECTILS` class of the AOP Utilities framework to create an agent object `proxy`, and pass the target object` myService` and the cut object `Loggingaspect` as a parameter to the` CreateProxy` method.Finally, we call the `proxy` 'dosomething` method, and the Aop Utilities framework trigger the corresponding notification method before and after the method executes.
Through the AOP Utilities framework, developers can separate attention point logic from the business logic of the application to achieve modularity and reusedability.This allows us to better maintain and expand applications.
