Java Custom Annotations

In spring applications, annotations are often used to develop, which facilitates faster development.

Describe the custom annotations:

First, custom annotations create a new @interface, which is an annotated interface that has several annotations on this interface:

　　　　　　@Documented markup Generation Javadoc

@Retention the lifetime of the annotations, the values are:

Take value	Describe
SOURCE	Valid in the source file (that is, the source file is reserved, and the boxed box is picked).
CLASS	Valid in class file (that is, class is reserved, and the boxed box is picked).
RUNTIME	Valid at run time (that is, run-time retention)

@Target the target of the label, the value is

CONSTRUCTOR	Used to describe the constructor (lead Bento).
FIELD	Used to describe the domain (lead bento).
Local_variable	Used to describe local variables (pick-up bento).
METHOD	Used to describe a method.
Package	Used to describe the package (pick box).
PARAMETER	Used to describe parameters.
TYPE	Used to describe a class or interface (even an enum).

@Inherited Tag Inheritance Relationships

Example: Create an annotation that acts on a class @person

1. First create an annotation class person

　　　　　　　　

 Packagecom.wuyu.annotation;Importjava.lang.annotation.Documented;ImportJava.lang.annotation.ElementType;Importjava.lang.annotation.Retention;ImportJava.lang.annotation.RetentionPolicy;ImportJava.lang.annotation.Target, @Documented @target (elementtype.type) @Retention (retentionpolicy.runtime) Public@InterfacePerson {String name ()default""; intAge ()default0;}

2. Create a test class

 Packagecom.wuyu.annotation; @Person (name= "Test") Public classTest { Public Static voidMain (string[] args) {getpersion (Test.class); }     Public Static voidGetpersion (class<?>c) {        if(C.isannotationpresent (person).class) { person person= C.getannotation (person.class); if(Person! =NULL) {System.out.println ("Name=" + person.name () + ", age=" +person.age ()); }        }    }}

3. Implementation results:

Name=test,age=0

Java Custom Annotations