UUID HEX as Primary Key : Primary Key « Hibernate « Java Tutorial

1. Java Tutorial
2. Hibernate
3. Primary Key

File: Main.java

import java.util.Date;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;

public class Main {
  public static void main(String[] args) throws Exception {
    HibernateUtil hibernateUtil = new HibernateUtil();
    hibernateUtil
        .executeSQLCommand("create table CD(id varchar,title varchar,artist varchar,purchaseDate date,cost decimal(6,2))");

    Session session = hibernateUtil.getSession();
    CD cd = new CD();

    
    session.save(cd);
    session.flush();

    session.close();
    hibernateUtil.checkData("select * from CD");
  }
}

File: CD.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-mapping 
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping> 
  <class name="CD" table="cd">
    <id name="Id" type="string" unsaved-value="null">
      <column name="ID" sql-type="text" not-null="true"/> 
      <generator class="uuid.hex"/>
    </id>

    <property name="title"/>
    <property name="artist"/>
    <property name="purchasedate" type="date"/> 
    <property name="cost" type="double"/> 
  </class>
</hibernate-mapping>

File: CD.java

import java.util.Date;

  public class CD {
    String id;
    String title; 
    String artist;
    Date  purchaseDate; 
    double cost;

    public CD() {
    }

    public CD(String title, String artist, Date purchaseDate, double cost) {
      this.title = title;
      this.artist = artist;
      this.purchaseDate = purchaseDate;
      this.cost = cost;
    }

    public void setId(String id) { 
      this.id = id;
    }

    public String getId(){ 
      return id;
    }

    public void setTitle(String title) { 
      this.title = title;
    }

    public String getTitle() { 
      return title;
    }

    public void setArtist(String artist) { 
       this.artist = artist;
    }

    public String getArtist() { 
      return artist;
    }

    public void setPurchasedate(Date purchaseDate) { 
      this.purchaseDate = purchaseDate;
    }

    public Date getPurchasedate() { 
      return purchaseDate;
    }

    public void setCost(double cost) { 
      this.cost = cost;
    }

    public double getCost() { 
      return cost;
    }
}

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="CD.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

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;
  Configuration config;
  
  public HibernateUtil() throws Exception{
    config = new Configuration().configure();

    
    SessionFactory sessionFactory = config.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 Configuration getConfiguration(){
    return config;
  }
  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("");
    }
  }
}

21.21.Primary Key
	21.21.1.	Use Long AS ID
	21.21.2.	Use Int As ID which starts from 0
	21.21.3.	UUID HEX as Primary Key
	21.21.4.	Composed ID