@Target 的ElemenType釋義

Element	應用類型	釋義
ElementType.TYPE	類	Can be applied to any element of a class
ElementType.FIELD	成員變量	Can be applied to a field
ElementType.PARAMETER	方法參數	Can be applied to method parameters
ElementType.CONSTRUCTOR	構造器	Can be applied to constructors
ElementType.LOCAL_VARIABLE	局部變量	Can be applied to local variables
ElementType.ANNOTATION_TYPE	註解類型	Indicates that the declared type itself is an annotation type

參考《Annotations in Java: @Target and @Retention》

註解文章《Java基礎加強總結(一)——註解(Annotation)》