Spring Boot中类级别和方法级别的注释方面（NullPointerException）

Question

@RestController
@SimpleAnnotation
public class HelloController{
    private static final Logger LOGGER = LoggerFactory.getLogger(HelloController.class);
    
    @GetMapping("/hello")
    @SimpleAnnotation(isAllowed=true)
    public String helloController(){
        final String methodName = "helloController";
        callAnotherMerhod();
        LOGGER.info("HelloController for method : {}", methodName);
        return "Hello";
    }

    private void callAnotherMethod(){

    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.TYPE})
public @interface SimpleAnnotation {

    boolean isAllowed() default false;
}

@Aspect
@Component
public class SimpleAspect {
    private static final Logger LOGGER = LoggerFactory.getLogger(SimpleAspect.class);

    @Around(value = "@within(simpleAnnotation) || @annotation(simpleAnnotation)", argNames = "simpleAnnotation")
    public Object simpleAnnotation(ProceedingJoinPoint proceedingJoinPoint, SimpleAnnotation simpleAnnotation) throws Throwable{
        LOGGER.info("Simple annotation value: {}, ASPECT-LOG {}", simpleAnnotation.isAllowed(),proceedingJoinPoint.getSignature().getName());
        return proceedingJoinPoint.proceed();
    }
}

当我运行应用程序并点击http://localhost:8080/hello时，一切都很好：

2020-11-09 11:36:48.230  INFO 8479 --- [nio-8080-exec-1] c.s.springaop.aspects.SimpleAspect       : Simple annotation value: true, ASPECT-LOG helloController

2020-11-09 11:36:48.246  INFO 8479 --- [nio-8080-exec-1] c.s.s.controller.HelloController         : HelloController for method : helloController

但是，如果我删除了方法上的注释：

@GetMapping("/hello")
    public String helloController(){
        final String methodName = "helloController";
        callAnotherMethod();
        LOGGER.info("HelloController for method : {}", methodName);
        return "Hello";
    }

然后SimpleAnnotation参数变为null，aspect方法抛出NullPointerException。

@Around(value = " @annotation(simpleAnnotation) || @within(simpleAnnotation)", argNames = "simpleAnnotation")

    @Around(value = "@within(simpleAnnotation) || @annotation(simpleAnnotation) || @within(simpleAnnotation)", argNames = "simpleAnnotation")

这似乎起作用了，但这是一个好的解决办法吗？

编辑：此解决方案也不起作用。如果我在类和方法级别上都有注释，假设类级别的注释值为false，而方法级别为true，那么注释值将为false。

Answer 1

要解决NPE，可以将切入点指示符(@inne和@annotation)重构为同一方面中的两个不同的建议方法。

基于ISAlloved值处理的逻辑可以保存在一个公共方法中，并从两个advice方法调用。

举例说明：

@Aspect
@Component
public class SimpleAspect {

    @Around(value = "@annotation(simpleAnnotation) && !@within(my.package.SimpleAnnotation)", argNames = "simpleAnnotation")
    public Object simpleAnnotationOnMethod(ProceedingJoinPoint proceedingJoinPoint, SimpleAnnotation simpleAnnotation)
            throws Throwable {
        System.out.println("Simple annotation value:" + simpleAnnotation.isAllowed() + " , ASPECT-LOG :"
                + proceedingJoinPoint.getSignature().getName());
        process(simpleAnnotation);
        return proceedingJoinPoint.proceed();
    }

    @Around(value = "@within(simpleAnnotation)", argNames = "simpleAnnotation")
    public Object simpleAnnotationOnType(ProceedingJoinPoint proceedingJoinPoint, SimpleAnnotation simpleAnnotation)
            throws Throwable {
        System.out.println("Simple annotation value:" + simpleAnnotation.isAllowed() + " , ASPECT-LOG :"
                + proceedingJoinPoint.getSignature().getName());
        process(simpleAnnotation);
        return proceedingJoinPoint.proceed();
    }

    private void process(SimpleAnnotation simpleAnnotation) {
        // advice logic
    }
}