学步园

@SuppressWarnings("unchecked")  
public <T> List<T> getAll(Class<T> clazz) {  
String className = clazz.getSimpleName();  
StringBuffer jpql = new StringBuffer("select o from ");  
jpql.append(className).append(" o ");  
return em.createQuery(jpql.toString()).getResultList();  
}