Use ASPECTJ Weaver to realize the horizontal cut surface of the Java class library
Use ASPECTJ Weaver to implement the horizontal section of the Java class library
Overview:
ASPECT is a programming idea for object-oriented programming. It is used to separate the complicated and maintenance of code by separating the Cross-Cutting Concerns from the main business logic.With the ASPECTJ Weaver, we can easily implement the horizontal cutting function in the Java library.This article will introduce how to use ASPECTJ Weaver to achieve horizontal cutting planes in the Java library and provide some Java code examples.
What is cross -cutting attention point:
Cross -cutting attention points refer to code fragments that have nothing to do with core business logic, such as log records, transaction management, abnormal processing, etc.Such functions will be widely used throughout the program, so separating it can improve the replication and maintenance of the code.
Aspectj weaver Introduction:
ASPECTJ Weaver is part of the ASPECTJ project. It is a Java bytecode tool that can be woven the cut surface code into the target class during compilation or runtime to achieve the function of cross -section attention.
Implementation steps:
1. Download and install ASPECTJ Weaver: You can download Aspectj Weaver from the official website of Aspectj and install it into the local development environment.
2. Create a Java project: Use ECLIPSE or other IDE to create a Java project and configure the related dependence of Aspectj Weaver.
3. Define a cut -off class: Create a Java class to define the logic of the cut surface.In the cut type, the pointcut and notification can be defined.
The cutting point defines the logic of where to apply the cut surface, and the notification defines the code logic executed at the cut point.
4. Compile and knitting into the cut surface: Use ASPECTJ Weaver to compile items and woven the cutting code into the target class.Can be woven during or runtime.
5. Test the cutting function: run the application, and test whether the function of the cut surface is working as expected.
Example code:
Below is an example, showing how to use Aspectj Weaver to implement the function of logging horizontal section in the Java library.
Cut the surface:
import org.aspectj.lang.annotation.*;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
@Aspect
public class LoggingAspect {
@Pointcut("execution(* com.example..*(..))")
public void loggingPointcut() {}
@Before("loggingPointcut()")
public void beforeAdvice(JoinPoint joinPoint) {
System.out.println("Entering method: " + joinPoint.getSignature().getName());
}
@AfterReturning(pointcut = "loggingPointcut()", returning = "result")
public void afterReturningAdvice(JoinPoint joinPoint, Object result) {
System.out.println("Exiting method: " + joinPoint.getSignature().getName());
System.out.println("Returning value: " + result);
}
@AfterThrowing(pointcut = "loggingPointcut()", throwing = "exception")
public void afterThrowingAdvice(JoinPoint joinPoint, Exception exception) {
System.err.println("Error in method: " + joinPoint.getSignature().getName());
System.err.println("Exception: " + exception.getMessage());
}
}
Target class:
package com.example;
public class Calculator {
public int add(int a, int b) {
return a + b;
}
public int divide(int a, int b) {
if (b == 0) {
throw new ArithmeticException("Divisor cannot be zero");
}
return a / b;
}
}
app:
package com.example;
public class Main {
public static void main(String[] args) {
Calculator calculator = new Calculator();
System.out.println(calculator.add(2, 3));
try {
System.out.println(calculator.divide(6, 0));
} catch (ArithmeticException e) {
System.err.println("Exception caught: " + e.getMessage());
}
}
}
Use ASPECTJ Weaver to compile and knit the cut surface:
Save the above code into the corresponding file and compile the project through Aspectj Weaver.You can use the aspectj plugin in the command line tool AJC or IDE.
Summarize:
By using ASPECTJ Weaver, we can easily implement the function of horizontal cutting surfaces in the Java class library.By defining cut points and notifications, we can insert the cutting logic before and after the specific method of the target class.Doing this can separate the core business logic with the focus of the code that has nothing to do with it, and improve the replication and maintenance of the code.
