Spring-AOP

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface TimePrinter {
}
@Aspect
@Component
@Slf4j
public class TimePrinterAspect {
    @Around("@annotation(printer)")
    public Object doAround(ProceedingJoinPoint joinPoint, TimePrinter printer) throws Throwable {
        Object ret;
        String method = getMethod(joinPoint);
        long start = System.currentTimeMillis();
        try {
            ret = joinPoint.proceed(joinPoint.getArgs());
        } catch (Throwable throwable) {
            log.error("TimePrinterAspect, invoke_error, method:{}", method, throwable);
            throw throwable;
        }
        log.info("TimePrinterAspect, invoke_success, method:{}, cost:{}ms", method, System.currentTimeMillis() - start);
        return ret;
    }
    private String getMethod(ProceedingJoinPoint joinPoint){
        return joinPoint.getSignature().getDeclaringTypeName().substring(
                joinPoint.getSignature().getDeclaringTypeName().lastIndexOf(".")) + "." +
                joinPoint.getSignature().getName();
    }
}

Spring是如何实现AOP的

• Spirng会把类装载到IOC容器中
• 当需要创建对象时，会直接从IOC容器中获取
• 从IOC容器中获取对象时，发现对象需要进行增强时就会生成代理对象，将增强部分生成到代理类中
• 实际业务中调用的是增强后的代理对象，由代理对象再去调用目标对象，代理对象相当于做了一层包装

https://www.jianshu.com/p/6cd83774a312