How to query on a month for a date with Hibernate criteria

Question

I need to use criteria to query a database. The data I'm searching has a date, say 'startDate' and I have a month say 0 for January, I need to extract all data where startDate has month = 0; in sql I'd use something like 'where month(startDate) = 0' but I don't know how to do this with hibernate criteria and if it's possible at all. Can you help me? Thank you guys. Luca.

Answer 1

With criteria, I think you'll have to write your own expression class. Something like this should work (not tested, though):

public class MonthEqExpression implements Criterion {

    private final String propertyName;
    private final int month;

    public MonthEqExpression(String propertyName, int month) {
        this.propertyName = propertyName;
        this.month = month;
    }

    @Override
    public String toSqlString(Criteria criteria, CriteriaQuery criteriaQuery)
        throws HibernateException {
            String[] columns = criteriaQuery.findColumns(propertyName, criteria);
            if (columns.length!=1) {
                throw new HibernateException("monthEq may only be used with single-column properties");
            }
            return "month(" + columns[0] + ") = ?";
        }

    @Override
    public TypedValue[] getTypedValues(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        return new TypedValue[] {new TypedValue(IntegerType.INSTANCE, month, EntityMode.POJO)};
    }

    @Override
    public String toString() {
        return "month(" + propertyName + ") = " + month;
    }
}

And then, you can use this expression in a criteria:

criteria.add(new MonthEqExpression("startDate", 0));

Answer 2

The answer above didn't work for me, but with a few changes it's working now.

public class MonthEqExpression implements Criterion {
    private final String propertyName;
    private final Long month;

    public MonthEqExpression(String propertyName, Long month) {
        this.propertyName = propertyName;
        this.month = month;
    }

    @Override
    public String toSqlString(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        String[] columns = criteriaQuery.getColumns(propertyName, criteria);
        if (columns.length != 1) {
            throw new HibernateException("monthEq may only be used with single-column properties");
        }
        return "extract(month from " + columns[0] + ") = ?";
    }

    @Override
    public TypedValue[] getTypedValues(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        return new TypedValue[] {new TypedValue(criteriaQuery.getIdentifierType(criteria), month, EntityMode.POJO)};
    }

    @Override
    public String toString() {
        return "extract(month from " + propertyName + ") = " + month;
    }
}

And then, you can use this expression in a criteria:

criteria.add(new MonthEqExpression("startDate", new Long(1)));