com.usetheindexluke.FewerColumnsHibernate.java Source code

Introduction

Here is the source code for com.usetheindexluke.FewerColumnsHibernate.java

Source

package com.usetheindexluke;

/**
 * Demonstrates a Projection to select only selected columns from a join.
 * The data is accessed via a Map that might, possibly, lead to runtime problems.
 * Consider using the DTO approach demonstrated in the FewerColumnsJPA sample
 * or
 * the byte-code instrumentation demonstrated in FewerColumnsInstrumentedHibernate.
 */

/* "Use The Index, Luke" by Markus Winand is licensed under a Creative Commons
 * Attribution-Noncommercial-No Derivative Works 3.0 Unported License. 
 * 
 *                     http://Use-The-Index-Luke.com/
 */

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;

import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.util.Map;

public class FewerColumnsHibernate {
    public static void main(String[] args) {
        Session session = new Configuration().configure().buildSessionFactory().openSession();
        try {
            Criteria q = session.createCriteria(Sales.class, "sales");
            q.add(Restrictions.gt("saleDate", getSixMonthAgo()));
            q.createAlias("employee", "employee");
            q.setProjection(Projections.projectionList().add(Projections.property("sales.saleDate"), "saleDate")
                    .add(Projections.property("sales.eurValue"), "eurValue")
                    .add(Projections.property("employee.lastName"), "lastName")
                    .add(Projections.property("employee.firstName"), "firstName"));
            q.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);

            List<Map> result = q.list();

            for (Map s : result) {
                String txt = " Employee: " + s.get("lastName") + " date: " + s.get("saleDate") + " EUR value: "
                        + s.get("eurValue");
                // System.out.println(txt);
            }
        } finally {
            session.close();
        }
    }

    // calculating the boundary date on the client side, avoiding
    // interoperability problems, especially since HQL doens't provide
    // INTERVAL calculations
    // http://opensource.atlassian.com/projects/hibernate/browse/HHH-2434
    static Date getSixMonthAgo() {
        Calendar c = Calendar.getInstance();
        c.add(Calendar.MONTH, -6);
        c.set(Calendar.HOUR, 0);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        return c.getTime();
    }
}