I am using reflection to see if an annotation that is attached to a property of a class, is of a specific type. Current I am doing:
if("javax.validation.Valid".equals(annotation.annotationType().getName())) {
...
}
Which strikes me as a little kludgey because it relies on a string that is a fully-qualified class-name. If the namespace changes in the future, this could cause subtle errors.
I would like to do:
if(Class.forName(annotation.annotationType().getName()).isInstance(
new javax.validation.Valid()
)) {
...
}
But javax.validation.Valid
is an abstract class and cannot be instantiated. Is there a way to simulate instanceof
(or basically use isInstance
) against an interface or an abstract class?
Are you just looking for
if (annotation.annotationType().equals(javax.validation.Valid.class)){}
?
Or even simpler:
if (annotation instanceof Valid) { /* ... */ }
Just for completeness' sake, another possibility is
if (this.getClass().isAnnotationPresent(MyCustomAnnotation.class)) {
Ok, I guess I should have done a little more research before posting the question. I discovered that I could use Class.isAssignableFrom(Class<?> cls)
:
import javax.validation.Valid;
if(Valid.class.isAssignableFrom(annotation.annotationType())) {
...
}
This seems to do the job. I'm not sure if there are any caveats to using this approach, though.
Since an annotation is just a class, you can simply use an == compare:
if (annotation.annotationType() == Valid.class) { /* ... */ }
来源:https://stackoverflow.com/questions/3348363/checking-if-an-annotation-is-of-a-specific-type