code

package com.auroradev.auroraserver.storage;

import org.hibernate.Session;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Root;
import java.util.List;

public class QueryBuilder<T> {
    private Session session;
    private CriteriaBuilder criteriaBuilder;
    private CriteriaQuery<T> criteriaQuery;
    private Root root;

    public QueryBuilder(Session session, Class<T> tClass) {
        this.session = session;
        criteriaBuilder = session.getCriteriaBuilder();
        criteriaQuery = criteriaBuilder.createQuery(tClass);
        root = criteriaQuery.from(tClass);
    }

    public QueryBuilder<T> where(String property, Object value) {
        criteriaQuery = criteriaQuery.where(criteriaBuilder.equal(root.get(property), value));

        return this;
    }

    public QueryBuilder<T> orderBy(String property, String direction) {
        switch (direction.toLowerCase()) {
            case "asc":
                criteriaQuery = criteriaQuery.orderBy(criteriaBuilder.asc(root.get(property)));
                return this;
            case "desc":
                criteriaQuery = criteriaQuery.orderBy(criteriaBuilder.desc(root.get(property)));
                return this;
        }

        return this;
    }

    public T getSingleResult() {
        return session.createQuery(criteriaQuery).getSingleResult();
    }

    public List<T> getResultSet() {
        return session.createQuery(criteriaQuery).list();
    }
}