When you want to dynamically replace Annotation in Java8

background

It's not a very common story, but you may want to dynamically change a class that has annotations like @Data (key = "1") to @Data (key = "2").

solution

Java8 seems to have additional functions in such cases, so I referred to the following site.

• https://rationaleemotions.wordpress.com/2016/05/27/changing-annotation-values-at-runtime/

A little simpler

public class DynamicAnnotationReplaceUtils {
    private static final String ANNOTATIONS = "annotations";
    private static final String ANNOTATION_DATA = "annotationData";

    /**
     *Replaces an annotation of one class with another annotation.
     *
     * @since
     *
     * @param targetClazz This class sets the annotation to be replaced.
     * @param originalOne Annotation of the replacement source.
     * @param newOne Annotation to replace. It will often be an instance of a class that extends the annotation of the replacement source.
     */
  public static void annotationReplacedBy(Class<?> targetClazz, String originalName, Annotation newOne) {
        try {
            @SuppressWarnings("all")
            Method method = Class.class.getDeclaredMethod(ANNOTATION_DATA, null);
            method.setAccessible(true);

            Object annotationData = method.invoke(targetClazz);

            Field annotations = annotationData.getClass().getDeclaredField(ANNOTATIONS);
            annotations.setAccessible(true);

            @SuppressWarnings("unchecked")
            Map<Class<? extends Annotation>, Annotation> map =
                    (Map<Class<? extends Annotation>, Annotation>) annotations.get(annotationData);

            Annotation original = map.entrySet().stream().filter(e -> {
                return e.getKey().getSimpleName().equals(originalName());
            }).findFirst().get().getValue();

            if (original == null) {
                throw new IllegalArgumentException(
                        String.format("Class(%s) has not %s annotaion.",
                                targetClazz.getCanonicalName(), originalName));
            }

            map.put(original, newOne);
        } catch (Exception ex) {
            throw new IllegalArgumentException(ex);
        }
    }

How to Use

DynamicAnnotationReplaceUtils.annotationReplacedBy(AnnotatedCalss.class, "Data", new ReplacedData()), 

What is the annotation to replace?

Definition of replacement source annotation

@Documented
@Retention(RetentionPolicy.RUNTIME)
public @interface Data {
    public abstract String key();
}

Definition of replacement annotation

public ReplacedData implements Data {
    public  String key() {
         return "2";
    }
}

Class with substitution source annotation

@Data(key = "1")
public TestData() {
}