Spring AOP自定义注释，使用注释参数获取Null

Question

@Around("@annotation(logExecutionTime) || @within(logExecutionTime)")
public Object logExecutionTime(ProceedingJoinPoint joinPoint, LogExecutionTime logExecutionTime) throws Throwable {
    final Logger logger = LoggerFactory.getLogger(joinPoint.getTarget().getClass());

    final String name = joinPoint.toShortString();
    final StopWatch stopWatch = new StopWatch(name);

    stopWatch.start(name);
    try {
      return joinPoint.proceed();

    } finally {
      stopWatch.stop();
      if (logExecutionTime.value()) {
        logger.info(joinPoint.getSignature().getName() + ".time=", stopWatch.getTotalTimeSeconds());
      }
    }
  }

@Around("@within(logExecutionTime) || @annotation(logExecutionTime)")

@Around("@within(logExecutionTime)")
public Object logExecutionTimeClassLevel(ProceedingJoinPoint joinPoint, LogExecutionTime logExecutionTime) throws Throwable {
    return logExecutionTimeMethodLevel(joinPoint, logExecutionTime);
  }

@Around("@annotation(logExecutionTime)")
public Object logExecutionTimeMethodLevel(ProceedingJoinPoint joinPoint, LogExecutionTime logExecutionTime) throws Throwable {
    final Logger logger = LoggerFactory.getLogger(joinPoint.getTarget().getClass());

    final String name = joinPoint.toShortString();
    final StopWatch stopWatch = new StopWatch(name);

    stopWatch.start(name);
    try {
      return joinPoint.proceed();

    } finally {
      stopWatch.stop();
      if (logExecutionTime.value()) {
        logger.info(joinPoint.getSignature().getName() + ".time=", stopWatch.getTotalTimeMillis());
      }
    }

班级水平

@LogExecutionTime
@Component
public class CleanUpService implements ICleanUpService { ... }

方法级

@Scheduled(fixedDelay = 100)
@LogExecutionTime(false)
public void processMessageQueue() { ... }

Answer 1

我来运行您的示例，并复制与您的示例相同的示例，当涉及到运行时表达式时，这是同样奇怪的，因为当您在类级别上指定注释时，您编写了这个表达式

@Around(" @within(logExecutionTime) || @annotation(logExecutionTime) ")

对于您的类，点剪切将计算为true（您注释的事件在joinpoint.gettarget().getclass().getAnnotations()中可用）

现在，当涉及到绑定变量时，编译器检查所有表示将@intern(logExecutionTime)绑定到变量logExecutionTime和@annotation(logExecutionTime)绑定到同一变量的表达式，如果该方法没有被注释，它将ge null,=>重写初始with，这将导致您提到的所有senarios。