java - 如何将基于注释的语法转换为原生 AspectJ 语法

Question

我对aspectj 及其语法有一些疑问。我在 java 文件上写了一些东西，我想将其转换为 .aj 文件，因为我认为这更容易，但我找不到可遵循的教程。

这是我的代码:

@Aspect
public class Aspect{

    @Pointcut("@annotation(annotationVariableName)")
    public void annotationPointCutDefinition(Annotation annotationVariableName){
    }

    @Pointcut("execution(* *(..))")
    public void atExecution(){}

    @Around("annotationPointCutDefinition(withTransactionVariableName) && atExecution()")
    public Object aroundAdvice(ProceedingJoinPoint joinPoint, Annotation annotationVariableName) throws Throwable {
        boolean parameter= annotationVariableName.parameter();
            Object returnObject = null;

            try {
                returnObject = joinPoint.proceed();
            } catch (Throwable throwable) {
                throw throwable;
            }
            return returnObject;
    }
}

有人可以帮我解决这个问题吗？谢谢!

Answer 1

我编了一个小例子MCVE与您对事务管理的评论有关，以便使代码及其日志输出更清晰一些:

注释:

package de.scrum_master.app;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Transaction {
  boolean myFlag();
}

驱动程序应用程序:

请注意，有两种方法带有注释，一种则没有。

package de.scrum_master.app;

public class Application {
  public static void main(String[] args) {
    Application application = new Application();
    application.doSomething();
    application.doSomethingElse();
    application.doSomethingWeird();
  }

  @Transaction(myFlag = true)
  public void doSomething() {
    System.out.println("Doing something");
  }

  public void doSomethingElse() {
    System.out.println("Doing something else\n");
  }

  @Transaction(myFlag = false)
  public void doSomethingWeird() {
    System.out.println("Doing something weird");
    throw new RuntimeException("oops");
  }
}

方面:

package de.scrum_master.aspect;

import org.aspectj.lang.SoftException;

import de.scrum_master.app.Transaction;

public aspect TransactionAspect {
  pointcut hasAnnotation(Transaction myAnnotation) : @annotation(myAnnotation);

  pointcut methodExecution() : execution(* *(..));

  Object around(Transaction myAnnotation) : methodExecution() && hasAnnotation(myAnnotation) {
    System.out.println(thisJoinPoint + " -> " + myAnnotation);
    boolean parameter = myAnnotation.myFlag();
    System.out.println("Transaction start");
    try {
      Object result = proceed(myAnnotation);
      System.out.println("Transaction commit\n");
      return result;
    } catch (Exception e) {
      System.out.println("Transaction roll-back\n");
      // Native AspectJ advices must not return checked exceptions, only runtime exceptions.
      // So we soften the caught exception, just in case.
      throw new SoftException(e);
    }
  }
}

控制台日志:

execution(void de.scrum_master.app.Application.doSomething()) -> @de.scrum_master.app.Transaction(myFlag=true)
Transaction start
Doing something
Transaction commit

Doing something else

execution(void de.scrum_master.app.Application.doSomethingWeird()) -> @de.scrum_master.app.Transaction(myFlag=false)
Transaction start
Doing something weird
Transaction roll-back

Exception in thread "main" org.aspectj.lang.SoftException
    at de.scrum_master.app.Application.doSomethingWeird_aroundBody3$advice(Application.java:22)
    at de.scrum_master.app.Application.doSomethingWeird(Application.java:1)
    at de.scrum_master.app.Application.main(Application.java:8)
Caused by: java.lang.RuntimeException: oops
    at de.scrum_master.app.Application.doSomethingWeird_aroundBody2(Application.java:23)
    at de.scrum_master.app.Application.doSomethingWeird_aroundBody3$advice(Application.java:17)
    ... 2 more

顺便说一句，如果您同意匿名切入点，则无需单独声明它们。你可以这样做:

具有匿名切入点的方面变体:

package de.scrum_master.aspect;

import org.aspectj.lang.SoftException;

import de.scrum_master.app.Transaction;

public aspect TransactionAspect {
  Object around(Transaction myAnnotation) : execution(* *(..)) && @annotation(myAnnotation) {
    System.out.println(thisJoinPoint + " -> " + myAnnotation);
    boolean parameter = myAnnotation.myFlag();
    System.out.println("Transaction start");
    try {
      Object result = proceed(myAnnotation);
      System.out.println("Transaction commit\n");
      return result;
    } catch (Exception e) {
      System.out.println("Transaction roll-back\n");
      // Native AspectJ advices must not return checked exceptions, only runtime exceptions.
      // So we soften the caught exception, just in case.
      throw new SoftException(e);
    }
  }
}