How to order result of hibernate based on a specific order

问题

I need to send a query to retrieve values that has a specific group of characters as following:

Lets say I am interested in 'XX' so it should search for any field that its value starts with 'XX' or has ' XX' (space XX). For example XXCDEF, PD XXRF and CMKJIEK XX are valid results.

I have following query that returns the correct results but I need to sort them in a way that it first return those with XX at the beginning then other results. As following:

XXABCD
XXPLER
XXRFKF
AB XXAB
CD XXCD
ZZ XXOI
POLO XX

Code

Criteria criteria = session.createCriteria(Name.class, "name")
                .add(Restrictions.disjunction()
                     .add(Restrictions.ilike("name.fname", fname + "%"))
                     .add(Restrictions.ilike("name.fname", "%" + " " + fname + "%"))
                    )
                .setProjection(Projections.property("name.fname").as("fname"));
        List<String> names = (List<String>) criteria.list();

回答1:

With JPQL (HQL):

select fname from Name
where upper(fname) like :fnameStart or upper(fname) like :fnameMiddle
order by (case when upper(fname) like :fnameStart then 1 else 2 end), fname

query.setParameter("fnameStart", "XX%");
query.setParameter("fnameMiddle", "% XX%");

With Criteria

With Criteria it's much trickier. Firstly, you have to resort to native SQL in the order clause. Secondly, you have to bind the variable.

public class FirstNameOrder extends Order {
    public FirstNameOrder() {
        super("", true);
    }

    @Override
    public String toSqlString(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        return "case when upper(FIRST_NAME) like ? then 1 else 2 end";
    }
}

The case expression syntax and the upper function name should be changed in accordance with your database (and the column name if it's different, of course).

It is easy to add this to the Criteria, but there is no API to bind the parameter.

I tried to trick Hibernate by passing in an unused variable to the custom sql restriction so that it is effectively used for the variable in the order by clause:

Criteria criteria = session.createCriteria(Name.class, "name")
   .add(Restrictions.disjunction()
      .add(Restrictions.ilike("name.fname", fname + "%"))
      .add(Restrictions.ilike("name.fname", "%" + " " + fname + "%")))
   .setProjection(Projections.property("name.fname").as("fname"))
   .add(Restrictions.sqlRestriction("1 = 1", fname + "%", StringType.INSTANCE))
   .addOrder(new FirstNameOrder())
   .addOrder(Order.asc("fname"));

and it works fine.

Obviously, this solution is not recommended and I suggest using JPQL for this query.

回答2:

Hibernate supports Order: http://docs.jboss.org/hibernate/orm/4.2/devguide/en-US/html/ch11.html#ql-ordering Because of the special criteria, I think you have to custom the Order in Hibernate. This link may help: http://blog.tremend.ro/2008/06/10/how-to-order-by-a-custom-sql-formulaexpression-when-using-hibernate-criteria-api/

回答3:

Run two selects, one filtered for all the strings starting with 'XX', the second filtered for the others.

回答4:

You can use Predicates in criteria... something like this:

public List<Name> findByParameter(String key, String value, String orderKey)

            CriteriaBuilder builder = this.entityManager.getCriteriaBuilder();
            CriteriaQuery<Name> criteria = builder.createQuery(this.getClazz());
            Root<Name> root = criteria.from(Name.getClass());
            criteria.select(root);
            List<Predicate> predicates = new ArrayList<Predicate>();
            predicates.add(builder.equal(root.get(key), value));
            criteria.where(predicates.toArray(new Predicate[predicates.size()]));
            if (orderKey!=null  && !orderKey.isEmpty()) {
                criteria.orderBy(builder.asc(root.get(orderKey)));
            }
            result = this.entityManager.createQuery(criteria).getResultList();

        return result;
}

回答5:

Stupid but it may work for your case.

Since you got your correct result you can just reconstruct your results as follows:

pick up all results starting with XX you put them into a list L1 and do the normal sort like Collections.sort(L1);
for all other results, do the same like Collections.sort(L2)as list of L2
At last , put them together

List newList = new ArrayList(L1);

newList.addAll(L2);

Please note. Collections.sort are following the natural ordering of its elements.

回答6:

If you don't want to sort the result in memory,you can modify your criteria,I'll show you the SQL

select * from table where fname like 'XX%' order by fname
union all
select * from table where fname like '% XX%' order by fname
union all
select * from table where fname like '% XX' order by fname

the result will be your order and alphabetical and then apply your filter.

来源：https://stackoverflow.com/questions/31281162/how-to-order-result-of-hibernate-based-on-a-specific-order

标签

java

hibernate

hibernate-criteria