Scalar SQL Query : Projections « Hibernate

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Java Tutorial » Hibernate » Projections

21. 15. 2. Scalar SQL Query

File: Main.java


import java.util.List;



import org.hibernate.Hibernate;

import org.hibernate.SQLQuery;

import org.hibernate.Session;



public class Main {

  public static void main(String[] args) throws Exception {

    HibernateUtil hibernateUtil = new HibernateUtil();

    hibernateUtil

        .executeSQLCommand("create table Product(id int, name varchar, description varchar, price decimal(6,2), supplierid int)");

     

    hibernateUtil

    .executeSQLCommand("create table Supplier (id int , name varchar)");



    hibernateUtil

    .executeSQLCommand("create table Software(id int, name varchar, description varchar, price decimal(6,2), supplierid int, version varchar)");



    

    Session session = hibernateUtil.getSession();



    Supplier superCorp = new Supplier();

    superCorp.setName("Supplier1");

    session.save(superCorp);

    

    Supplier megaInc = new Supplier();

    megaInc.setName("Supplier2");

    session.save(megaInc);        



    Product mouse = new Product("Product1","first product", 20.0);

    mouse.setSupplier(superCorp);

    superCorp.getProducts().add(mouse);

    session.flush();

    Product mouse2 = new Product("Product2","second product", 22.0);

    mouse2.setSupplier(superCorp);

    superCorp.getProducts().add(mouse2);        

    

    Product keyboard = new Product("Product3", "third product", 30.0);

    keyboard.setSupplier(megaInc);

    megaInc.getProducts().add(keyboard);



    Software webBrowser = new Software("Web Browser","new browser", 75.0, "2.0");

    webBrowser.setSupplier(superCorp);

    superCorp.getProducts().add(webBrowser);



    Software email = new Software("Email","email client", 49.99, "4.1 Edition");

    email.setSupplier(megaInc);

    megaInc.getProducts().add(email);    



    session.flush();

    

    

    

    String sql = "select avg(product.price) as avgPrice from Product product";

    

    SQLQuery query = session.createSQLQuery(sql);

    query.addScalar("avgPrice",Hibernate.DOUBLE);



    List results = query.list();



    System.out.println(results);

    

    

    

    session.close();

    hibernateUtil.checkData("select * from Product");

    hibernateUtil.checkData("select * from Software");

    hibernateUtil.checkData("select * from Supplier");

  }

}

File: Software.java


public class Software extends Product

{

    private String version;

    

    public Software()

    {

        super();

    }

    

    public Software(String name, String description, double price, String version)

    {

        super(name, description, price);

        this.setVersion(version);

    }



    public String getVersion()

    {

        return version;

    }

    public void setVersion(String version)

    {

        this.version = version;

    }

}

File: Software.hbm.xml


<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-mapping

   PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"

   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">



<hibernate-mapping>

   <joined-subclass name="Software" extends="Product">

      <key column="Id"/>

      <property name="version" type="string"/>

   </joined-subclass>

</hibernate-mapping>

File: Product.java


public class Product

{

    private int id;

    private Supplier supplier;

    

    private String name;

    private String description;

    private double price;

    

    public Product()

    {

        super();

    }

    

    public Product(String name, String description, double price)

    {

        super();

        this.name = name;

        this.description = description;

        this.price = price;

    }

    

    public String getDescription()

    {

        return description;

    }

    public void setDescription(String description)

    {

        this.description = description;

    }

    public int getId()

    {

        return id;

    }

    public void setId(int id)

    {

        this.id = id;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

 

    public Supplier getSupplier()

    {

        return supplier;

    }

    public void setSupplier(Supplier supplier)

    {

        this.supplier = supplier;

    }

    

    public double getPrice()

    {

        return price;

    }

    public void setPrice(double price)

    {

        this.price = price;

    }

}

File: Product.hbm.xml


<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-mapping

   PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"

   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">



<hibernate-mapping>

   <class name="Product">

      <id name="id" type="int">

         <generator class="increment"/>

      </id>



      <property name="name" type="string"/>

      <property name="description" type="string"/>

      <property name="price" type="double"/>

      <many-to-one name="supplier" class="Supplier" column="supplierId"/>



   </class>

   

   <query name="Product.HQLpricing">

     select product.price from Product product where product.price = 25.0

  </query>   

   <sql-query name="Product.SQLpricing">

   <return-scalar column="price" type="double"/>

     select product.price from Product as product where product.price = 25.0

  </sql-query>     

</hibernate-mapping>

File: Supplier.java


import java.util.ArrayList;

import java.util.List;



public class Supplier

{

    private int id;

    private String name;

    private List products = new ArrayList();

    

    public int getId()

    {

        return id;

    }

    public void setId(int id)

    {

        this.id = id;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

    public List getProducts()

    {

        return products;

    }

    public void setProducts(List products)

    {

        this.products = products;

    }

}

File: Supplier.hbm.xml


<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-mapping

   PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"

   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">



<hibernate-mapping>

   <class name="Supplier" >

      <id name="id" type="int">

         <generator class="increment"/>

      </id>



      <property name="name" type="string"/>

      <bag name="products" inverse="true" cascade="all,delete-orphan">

        <key column="supplierId"/>

        <one-to-many class="Product"/>

      </bag>





   </class>

</hibernate-mapping>

File: HibernateUtil.java


import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.ResultSetMetaData;

import java.sql.Statement;



import org.hibernate.HibernateException;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;



public class HibernateUtil {

  Session session;

  Statement st;

  public HibernateUtil() throws Exception{

    SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

    session = sessionFactory.openSession();



    // Load the JDBC driver.

    Class.forName("org.hsqldb.jdbcDriver");

    System.out.println("Driver Loaded.");

    // Establish the connection to the database.

    String url = "jdbc:hsqldb:data/tutorial";



    Connection conn = DriverManager.getConnection(url, "sa", "");

    System.out.println("Got Connection.");

    st = conn.createStatement();

  }

  public Session getSession(){

    return session;

  }

  public void executeSQLCommand(String sql) throws Exception {

    st.executeUpdate(sql);

  }



  public void checkData(String sql) throws Exception {

    ResultSet rs = st.executeQuery(sql);

    ResultSetMetaData metadata = rs.getMetaData();



    for (int i = 0; i < metadata.getColumnCount(); i++) {

      System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 

    }

    System.out.println("\n----------------------------------");



    while (rs.next()) {

      for (int i = 0; i < metadata.getColumnCount(); i++) {

        Object value = rs.getObject(i + 1);

        if (value == null) {

          System.out.print("\t       ");

        } else {

          System.out.print("\t"+value.toString().trim());

        }

      }

      System.out.println("");

    }

  }

}

File: hibernate.cfg.xml


<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

    "-//Hibernate/Hibernate Configuration DTD//EN"

    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->

        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>

        <property name="connection.url">jdbc:hsqldb:data/tutorial</property>

        <property name="connection.username">sa</property>

        <property name="connection.password"></property>



        <!-- JDBC connection pool (use the built-in) -->

        <property name="connection.pool_size">1</property>



        <!-- SQL dialect -->

        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>

        <!-- Enable Hibernate's current session context -->

        <property name="current_session_context_class">org.hibernate.context.ManagedSessionContext</property>



        <property name="hibernate.cache.use_second_level_cache">false</property>

        <property name="hibernate.cache.use_query_cache">false</property>

        

        <!-- Disable the second-level cache  -->

        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>        

        <!-- Echo all executed SQL to stdout -->

        <property name="show_sql">true</property>

        

        <!-- Mapping files -->

        <mapping resource="Product.hbm.xml"/>

        <mapping resource="Software.hbm.xml"/>

        <mapping resource="Supplier.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

Download: HibernateScalarSQLQuery.zip( 4,865 k)

21. 15. Projections
	21. 15. 1.	Select Specific Fields in a Entity with Criteria and Projections
	21. 15. 2.	Scalar SQL Query
	21. 15. 3.	Projection: Min
	21. 15. 4.	Projection: Max
	21. 15. 5.	Group Field
	21. 15. 6.	Projection: Count Distinct
	21. 15. 7.	AVG Projection
	21. 15. 8.	Hibernate demo code from Hibernate in action

Scalar SQL Query : Projections « Hibernate « Java Tutorial