code: @SuppressWarnings("unchecked")
     public void setExcerptProviderClass(String className)
     {
        try
        {
           Class<?> clazz = ClassLoading.forName(className, this);
           if (ExcerptProvider.class.isAssignableFrom(clazz))
           {
              excerptProviderClass = (Class<? extends ExcerptProvider>)clazz;
           }
           else
           {
              log.warn("Invalid value for excerptProviderClass, {} does " + "not implement ExcerptProvider interface.",
                 className);
           }
        }
        catch (ClassNotFoundException e)
        {
           log.warn("Invalid value for excerptProviderClass, class {} not found.", className);
        }
     }
docs: Sets the class name for the {@link ExcerptProvider} that should be used
  for the rep:excerpt pseudo property in a query.
  
  @param className
  the name of a class that implements {@link ExcerptProvider}.