Grails Groovy Hibernate | Hibernate Criteria Builder | Projection | Custom Projection | Group By Projection | PropertyProjection

Grails Groovy Hibernate | Hibernate Criteria Builder | Projection | Custom Projection | Group By Projection | PropertyProjection.

It's easy to add projection custom. We can add custom projection and custom group by property.

import org.hibernate.criterion.Projections
import org.hibernate.criterion.Projection
import org.hibernate.criterion.PropertyProjection
import org.hibernate.Criteria
import org.hibernate.criterion.CriteriaQuery
import org.hibernate.HibernateException
org.hibernate.criterion.ProjectionList projectionList = []

ProjectionList projectionList = []
projectionList.add(new PropertyProjection("id") {
    @Override
    public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) throws HibernateException {
        return "this_.id as y0_"
    }
})
projectionList.add(new PropertyProjection("created") {
    @Override
    public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) throws HibernateException {
        return "MAX(this_.created) as y1_"
    }
})
projectionList.add(Projections.groupProperty("belongsTo.id"))
PropertyProjection groupBy = new PropertyProjection("id", true) {
    @Override
    public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) throws HibernateException {
        return "belongsto1_.id as y1_"
    }

    @Override
    public String toGroupSqlString(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        return "belongsto1_.id"
    }
}
projectionList.add(groupBy)
Closure closure = {
    setProjection(projectionList)
}
List list =  Domain.createCriteria().list {
    and closure
}

But you want to make it simpler then you can use below function easily:

import org.hibernate.criterion.CriteriaSpecification
import org.hibernate.criterion.Projections
import org.hibernate.type.DoubleType
import org.hibernate.type.Type

resultTransformer(CriteriaSpecification.ALIAS_TO_ENTITY_MAP)
projections {
    groupProperty("id", "id")
    groupProperty("name", "name")
    addProjectionToList(Projections.sqlProjection(
            "sum(id * 0.2) as totalPrice",
            ["totalPrice"] as String[],
            [DoubleType.INSTANCE] as Type[],
    ), "complexSqlCalculation")
}