Java Spring Boot AOP不工作

我是Spring Boot和AOP的新手，我花了三天时间试图让它正常工作，但都没有用

我有一门课叫App。此类调用名为invokeRetrieveMethod的方法，该方法调用自动连线businessClass对象中的另一个方法。我只是试图记录运行带有自定义

@LogExecutionTime

注释的方法所需的时间，但运行代码时会出现空指针异常。请帮忙

@SpringBootApplication
public class App 
{
    @Autowired
    BusinessClass businessClass;

    public static void main( String[] args )
    {
        SpringApplication.run(App.class, args);
        System.out.println("Starting application...");

        App app = new App();
        app.invokeRetrieveSomething();
    }

    public void invokeRetrieveSomething() {
        businessClass.retrieveSomething();
    }
}

弹簧靴“豆”（？）

我的方面

@Aspect //specifies that this is an aspect
@Component //because we want this class to be turned into a bean in order for it to work supposedly
public class ExampleAspect {

    @Around("@annotation(LogExecutionTime)")
    public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {

        long start = System.currentTimeMillis(); //executed before the method annotated with @LogExecutionTime is executed.

        Object proceed = joinPoint.proceed();

        //everything below gets executed after the method.
        long executionTime = System.currentTimeMillis() - start;
        System.out.println(joinPoint.getSignature() + " executed in " + executionTime + "ms");

        return proceed;
    }
}

我的自定义批注

@Target(ElementType.METHOD) //tells us *where* this annotation will be applicable (ElementType.METHOD means on methods only)
@Retention(RetentionPolicy.RUNTIME) //states whether the annotation will be available to the jvm at runtime or not. by default, it's not.
public @interface LogExecutionTime {

}

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使用注释@enableSpectJautoproxy在App类中启用AspectJ

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阅读更多信息：

尝试在切入点表达式中使用完全限定类名：

@Around（@annotation（fully.qualified.LogExecutionTime）”）

您正在创建

应用程序的新实例。您应该从上下文中获取实例并调用该实例上的方法。
@Target(ElementType.METHOD) //tells us *where* this annotation will be applicable (ElementType.METHOD means on methods only)
@Retention(RetentionPolicy.RUNTIME) //states whether the annotation will be available to the jvm at runtime or not. by default, it's not.
public @interface LogExecutionTime {

}