package com.atlassian.plugins.rest.common.expand.resolver;
   
   import com.atlassian.plugins.rest.common.expand.EntityExpander;
   import com.atlassian.plugins.rest.common.expand.Expander;
   
   import static com.google.common.base.Preconditions.checkNotNull;
   
   /**
    * <p>An {@link EntityExpander} resolver that uses the {@link Expander} annotation for resolution.</p>
   * <p>Implementation must implement {@link #getEntityExpander(Expander)}</p>
   */
  public abstract class AbstractAnnotationEntityExpanderResolver implements EntityExpanderResolver {
      public boolean hasExpander(Class<?> type) {
          return checkNotNull(type).getAnnotation(Expander.class) != null;
      }
  
      public final <T> EntityExpander<T> getExpander(Class<? extends T> type) {
          final Expander expander = checkNotNull(type).getAnnotation(Expander.class);
          return expander != null ? (EntityExpander<T>) getEntityExpander(expander) : null;
      }
  
      /**
       * Retrieves the {@link EntityExpander} associated to the {@link Expander} annotation. The entity expander is created if necessary.
       *
       * @param expander the annotation
       * @return an instance of {@link EntityExpander}
       */
      protected abstract EntityExpander<?> getEntityExpander(Expander expander);
  }