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Polymorphic CriteriaQuery without inverse relationship

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鱼传尺愫
鱼传尺愫 2021-02-07 10:37

I have the following EJB structure. Don\'t wonder about Animal and Inventory, these classes are only here to demonstrate the structure in a simplified

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  • 日久生厌
    日久生厌 (楼主)
    2021-02-07 10:54

    If you are using EclipseLink, solution is simple. Modify the Path criteria to cast to RfIdTag:

    Path path = ((Path) from.join("idTag").as(RfIdTag.class)).get("code");



    If you are using Hibernate, replace your method with:
    


    public static  T fOwner(Class type, String catName) {
    CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
    CriteriaQuery criteriaQuery = criteriaBuilder.createQuery(type);
    Root fromType = criteriaQuery.from(type);
    Root fromRfId = criteriaQuery.from(RfIdTag.class);

    Path pathCode = fromRfId.get("code");
    Path pathIdTagType = fromType.get("idTag");
    Path pathIdTagRfId = fromRfId.get("id");

    CriteriaQuery select = criteriaQuery.select(fromType);
    select.where(
            criteriaBuilder.equal(pathCode, catName),
            criteriaBuilder.equal(pathIdTagType, pathIdTagRfId));

    TypedQuery q = em.createQuery(select);
    return q.getSingleResult();
}



    This makes a "join" ("a filtered cartesian product") between "T" and "RfIdTag".
    
    
    
             
    
                                                        
    
            
            
    
              
                
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