公共字段自动填充

自定义注解
公共字段有create_time,update_time,create_time,update_time。这四个字段变动在insert或者update操作时

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AutoFill {
    OperrationType value();// OperrationType为枚举类型，枚举insert，update两种操作
}

@Component
@Slf4j
@Aspect
public class AutoFillAspect {
    @Pointcut("@annotation(AutoFill)")
    public void pointCut(){}
    @Before("pointCut()")
    public void autoFill(JoinPoint joinPoint){
     MethodSignature signature =(MethodSignature) joinPoint.getSignature();
        String name = signature.getName();
        AutoFill annotation = signature.getMethod().getAnnotation(AutoFill.class);
        OperrationType value = annotation.value();
        Object[] args = joinPoint.getArgs();
        Object arg = args[0];
        LocalDateTime now = LocalDateTime.now();
        if(value.equals(OperrationType.INSERT)){
            try {
                Method setCreateTime = arg.getClass().getDeclaredMethod("setCreateTime", LocalDateTime.class);
               //...
                setCreateTime.invoke(arg,now);
            } catch (NoSuchMethodException e) {
                throw new RuntimeException(e);
            } catch (InvocationTargetException e) {
                throw new RuntimeException(e);
            } catch (IllegalAccessException e) {
                throw new RuntimeException(e);
            }

        }
        else System.out.println("这是更新");
    }
}

反射常见作用：
获取类的类名。父类，接口
创建类的实例对象
动态调用方法
访问属性
获取方法返回值类型，参数类型