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Thread: Java Reflection question

  1. #1
    Junior Member
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    Default Java Reflection question

    @MyAnnotation(name="someName",  value = "Hello World")
    public class TheClass {
    }
     
     
     
     
    public @interface MyAnnotation {
    	String   value();
            String   name();
    }
     
     
     
    import java.lang.annotation.Annotation;
     
    public class Test {
     
    	public static void main(String[] args) {		
    		Class aClass = TheClass.class;
    		Annotation annotation = aClass.getAnnotation(MyAnnotation.class);		
     
    		if(annotation instanceof MyAnnotation){
    		    MyAnnotation myAnnotation = (MyAnnotation) annotation;
    		    System.out.println("name: " + myAnnotation.name());
    		    System.out.println("value: " + myAnnotation.value());
    		}
    	}
     
    }

    I'm expecting output:
    name: someName
    value: Hello World

    but I get nothing.

    --- Update ---

    Removing the if loop throws NullPointerException which leads me to belive that annotation is not assigned.

    --- Update ---

    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
     
    @Retention(RetentionPolicy.RUNTIME)
    public @interface MyAnnotation {
    	String   value();
            String   name();
    }

    This fixed it.

  2. #2
    Member John Joe's Avatar
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    Default Re: Java Reflection question

    Why you need @ ?
    Whatever you are, be a good one

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