Here is a test class:
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
public class TestAnnotations {
@interface Annotate{}
@Annotate public void myMethod(){}
public static void main(String[] args) {
try{
Method[] methods = TestAnnotations.class.getDeclaredMethods();
Method m = methods[1];
assert m.getName().equals("myMethod");
System.out.println("method inspected ? " + m.getName());
Annotation a = m.getAnnotation(Annotate.class);
System.out.println("annotation ? " + a);
System.out.println("annotations length ? "
+ m.getDeclaredAnnotations().length);
}
catch(Exception e){
e.printStackTrace();
}
}
}
Here is my output :
method inspected ? myMethod
annotatio开发者_运维百科n : null
annotations length : 0
What I am missing to make annotations visible through reflection ?
Do I need an annotation processor even for just checking their presence ?In order to access an annotation at runtime, it needs to have a Retention policy of Runtime.
@Retention(RetentionPolicy.RUNTIME) @interface Annotate {}
Otherwise, the annotations are dropped and the JVM is not aware of them.
For more information, see here.
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