Unable to set SolrDocument annotation at RUNTIME

I am using Spring Data Solr and I have the following Solr document model class and have a corresponding SolrCrudRepository for this class

@SolrDocument(collection = "oldCollectionName")
public class TestDocument {

            @Id
            @Indexed(name = "id", type = "string")
            private String id;

            @Field(value = "name")
            private String name;

            @Field(value = "externalid")
            private Integer externalId;
}

I am trying to modify the annotation '@SolrDocument(collection = "oldCollectionName")' at runtime.

I have a Service which has the following method to find all documents using the repository and the model class

public List<TestDocument> getDocumentsByName(String name){

        String newSolrDocument = getModifiedSolrCollectionName();
        alterAnnotationValue(TestDocument.class, SolrDocument.class, newSolrDocument);

        SolrDocument solrDocument = TestDocument.class.getAnnotation(SolrDocument.class);

        LOGGER.info("Dynamically set SolrDocument Annotaation: "+solrDocument.collection());

        return testDocumentRepository.findByName(name);
    }

The code to alter annotation looks like this

   public void alterAnnotationValue(Class<?> targetClass, Class<? extends Annotation> targetAnnotation, Annotation targetValue) {
        try {
            Method method = Class.class.getDeclaredMethod(ANNOTATION_METHOD, null);
            method.setAccessible(true);

            Object annotationData = method.invoke(targetClass);

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

            Map<Class<? extends Annotation>, Annotation> map = (Map<Class<? extends Annotation>, Annotation>) annotations.get(annotationData);
            map.put(targetAnnotation, targetValue);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Using this I am correctly getting the newDocumentName set into the annotation map but when calling the testDocumentRepository's find method to find documents. The old collection name is getting picked.

Do I have to do something more for this to work? or I am missing anything?

For reference, I have followed the following tutorial http://www.baeldung.com/java-reflection-change-annotation-params