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How to use @Inherited meta-annotation in java project
- 王林forward
- 2023-05-10 13:34:06959browse
1. Read the source code document first
@Recorded
@Retention(Retention Policy. RUNTIME)
@Target(ElementType. Comments Type)
public@interfaceInherited{
}The above code annotation can be translated using Google. The rough meaning is
indicating automatic inheritance of annotation types. If there is an inherited meta-annotation in the annotation type declaration, and the user queries the annotation type on the class declaration, and the class declaration does not have an annotation of this type, the superclass of the class will automatically query the annotation type. This process will be repeated until an annotation of this type is found or the top of the class hierarchy is reached. If none of the superclasses has this type of annotation, the query will indicate that the class has no such annotation.
Please note that this meta-annotation type has no effect if you use it to annotate anything other than classes. Also note that this meta-annotation only results in inherited annotations from the superclass; invalid annotations on implemented interfaces.
As can be seen from the above description, the subclass of the annotation parent class using this annotation can inherit the annotation of the parent class.
2. Code test
2.1 Has @Inherited annotation
@Target(ElementType. Type)
@Retention(retention policy. RUNTIME)
@Inheritance
public @ interfaceInheritedTest {
string value();
}@InheritedTest(' Has inheritance')
publicclassPerson{
publicvoidmethod(){
}
publicvoidmethod2(){
}
} publicclassstudentextends person {
}Test:
publicclassTestInherited{
public static void main(String[]args){
CLaSS studentCLaSS=student . class;
if(student class . is notationpresent(inherited test . class)){
system . out . println(StudentClass . GetAnnotation(InheritedTest . Class)). value());
}
}
} Output:
2.2 No @Inherited annotation
@Target(ElementType.Type)
@Retention(Retention Policy.RUNTIME)
public @ interfacesinotinherited {
string value();
} @ IsNotInherited('Not owned inheritance')
publicclassPerson{
publicvoidmethod(){
}
publicvoidmethod2(){
}
} publicclassstudentextends person {
}Test:
publicclassTestInherited{
public static void main(String[]args){
CLaSS studentCLaSS=student . class;
if(StudentClass . is notationPresent(iSnotinerIded . Class)){
system . out . println(StudentClass . GetAnnotation(iSNOTiHerided . class) ). value());
}
}
}
Does not output tolerance, visible subclasses without @Inherited annotation This annotation will not be inherited.
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