I finally understood why Astyanax was not allowing me ColumnFamily with . My mistake was that I was defining the EntityManager with parameters (Object, String) instead of (Object, UUID)
ColumnFamily<UUID, String> columnFamily = new ColumnFamily< UUID, String>(
"Merchant", // Column Family Name
StringSerializer.get(), // Key Serializer
StringSerializer.get()); // Column Serializer
EntityManager<Merchant, UUID > entityPersister = new DefaultEntityManager.Builder<Merchant, UUID >()
.withEntityType(Merchant.class)
.withKeyspace(keyspace)
.withColumnFamily(columnFamily)
.build();