Spring Boot AOP不起作用

Question

我是Spring Boot和AOP的新手，我花了最后三天的時間讓它無法正常工作。

我有一門叫App的課。 此類調用一個稱為invokeRetrieveMethod的方法-該方法將在自動裝配的businessClass對象中調用另一個方法。 我只是試圖記錄運行帶有自定義@LogExecutionTime批注的方法所花費的時間，但是在運行代碼時出現空指針異常。 請幫忙！

@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();
    }
}

春季啟動“豆”（？）

@Component
public class BusinessClass {

    @LogExecutionTime
    public void retrieveSomething() {
        System.out.println("This is the retrieveSomething() method.");
    }
}

我的觀點

@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;
    }
}

我的自定義注釋

@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 {

}

Answer 1

使用注釋@EnableAspectJAutoProxy在App類中啟用AspectJ。有關更多信息， 請訪問： https ://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/EnableAspectJAutoProxy.html