注释接口 Scalar
@Retention(RUNTIME)
@Target(allowedTargets=PROPERTY)
@Target({TYPE,METHOD,ANNOTATION_TYPE})
public @interface Scalar
Generally speaking, this annotation does not need to be used,
and the scalar property does not need to be explicitly stated.
If the property is of type `List<E>`, it will be treated as
special collection property whose element type must be Java class/interface.
For example, one-to-many and many-to-many associations, and their `@
IdView` properties.
However, sometimes `List<E>` may be just a JSON field, and even nested structures can appear
(for example: `List<List<E>>`),
this is the need to explicitly use this annotation or any other annotation decorated by this annotation(eg: Serialized).