Reading Java Annotations: How to Retrieve Annotation Values

Java annotations are a powerful tool that help developers to provide metadata information about code. Annotations can be used to define attributes, methods, classes and more. Retrieving annotation values can be a bit of a challenge, but with the right approach, it is easy to do.

What are Java Annotations?

Java annotations are a form of metadata that provide information about Java code. Annotations can be used to define attributes, methods, classes and more. Annotations can also be used to provide additional context about code, such as the author, version, and other information.

How to Retrieve Annotation Values

Retrieving annotation values in Java can be done using the getAnnotation method. This method takes a class object as a parameter and returns the annotation object for that class. Once you have the annotation object, you can retrieve the values using the annotation's methods.

import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface MyAnnotation {
    String value();
}

@MyAnnotation(value = "Example")
public class MyClass {
    // Class body
}

public class Main {
    public static void main(String[] args) {
        Class<MyClass> obj = MyClass.class;
        MyAnnotation annotation = obj.getAnnotation(MyAnnotation.class);
        System.out.println(annotation.value());
    }
}

In the above example, we create a custom annotation called MyAnnotation with a single value value. We then apply this annotation to the MyClass class. In the main method, we retrieve the MyAnnotation object using the getAnnotation method and print out the value using the value method.

Conclusion

Java annotations are a powerful tool that can be used to provide metadata information about code. Retrieving annotation values can be done using the getAnnotation method and the annotation's methods. With the right approach, retrieving annotation values is easy and can provide valuable context about code.