[JavaSE] annotation-custom annotation and javase annotation Customization

[JavaSE] annotation-custom annotation and javase annotation Customization

Annotation classification:

Source code annotation

@ Override annotated with JDK during compilation

@ Autowired of Spring annotation during runtime

 

Syntax requirements for custom annotations

① Use the @ interface keyword to define the Annotation

② The Member is executed without any parameters or exceptions.

③ You can use defaut to specify a default value for the member.

④ The member type is restricted, including the original type and String Class Annotation Enumberation

⑤ If the annotation has only one member, the member name must be named value (). during use, the member name and value assignment number (=) can be ignored)

⑥ The annotation class can have no members, which is called the identifier annotation.

Package com. tsh. ano; import java. lang. annotation. documented; import java. lang. annotation. elementType; import java. lang. annotation. inherited; import java. lang. annotation. retention; import java. lang. annotation. retentionPolicy; import java. lang. annotation. target; // meta annotation @ Target ({ElementType. METHOD, ElementType. TYPE}) // scope @ Retention (RetentionPolicy. RUNTIME) // life cycle @ Inherited // can be Inherited @ incluented // generate document public @ interface Description {String desc (); String author (); int age () default 18;} // use the annotation class DescAnoDemo {@ Description (author = "taoshihan", desc = "hahaha") void show (){}}

 

Meta annotation: Annotation

Use custom annotations

Parse Annotation