JPQL检入参数不为null然后执行查询

Question

I have some parameters which can be null or can be not null.

What I want to do is to execute query only with parameters which are not null.

For example I have:

String param1;
String param2;

And I want to do something like this:

 If ( param1 != null && param2 != null ) {
    Query q = em.createQuery("SELECT a FROM Advert where a.property = param1 and a.property2= param2);
 }

 if( param1 == null && param2 != null ) {
    Query q = em.createQuery("SELECT a FROM Advert where  a.property2= param2")
 }

 if( param1 != null && param2 == null ) {
    Query q = em.createQuery("SELECT a FROM Advert where  a.property= param1");
 }

Is it possible to do this not using if statements but with jpql query string? ( because I have more than two parameters and it is not so convenient to check so many cases)

Answer 1

You can have something like this :

        CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
        CriteriaQuery<Advert> query = criteriaBuilder.createQuery(Advert.class);
        Root<Advert> advertRoot = query.from(Advert.class);         
        query.select(advertRoot);
        List<Predicate> criteria = new ArrayList<Predicate>();
        if(property != null){
            ParameterExpression<String> p =
                    criteriaBuilder.parameter(String.class, "property");
            criteria.add(criteriaBuilder.equal(advertRoot.get("property"), p));
        }
        if(property1 != null){
            ParameterExpression<String> p =
                    criteriaBuilder.parameter(String.class, "property1");
            criteria.add(criteriaBuilder.equal(advertRoot.get("property1"), p));
        }
        if (criteria.size() == 0) {
            throw new RuntimeException("no criteria");
        } else if (criteria.size() == 1) {
            query.where(criteria.get(0));
        } else {
            query.where(criteriaBuilder.and(criteria
                    .toArray(new Predicate[0])));
        }
        TypedQuery<Advert> q = em.createQuery(query);
        //set your query parameters here
        if (property != null) { q.setParameter("property", property); }
        if (property1 != null) { q.setParameter("property1", property1); }
        List<Advert> resultList = q.getResultList();