A little error on delete.

The Entity name is com.mastertheboss.model.SimpleProperty, change it at line 40
//Query query = em.createQuery("delete FROM com.sample.model.SimpleProperty p where p.key='"+p.getKey()+"'");
  Query query = em.createQuery("delete FROM com.mastertheboss.model.SimpleProperty p where p.key='"+p.getKey()+"'");
		
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