Aug 17, 2010

H2: Embedded Java DB: Getting Started

An embedded database system is a database management system (DBMS) which is tightly integrated with an application software that requires access to stored data, such that the database system is “hidden” from the application’s end-user and requires little or no ongoing maintenance. (Source: Wikipedia.org)

In this post I am going to show you how you could implement an embedded database within a Java application.

Download the Platform-Independent Zip.
Extract it into your library folder on your local installation.
Start Eclipse.
Create a new project.
Add the h2*.jar to the classpath of your new project.

Setup a entry point of your application as you create a new class containing the following code:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class Start {

  /**
   * @param args
   */
  public static void main(String[] args)
  {
    try
    {
      Class.forName("org.h2.Driver");
          Connection con = DriverManager.getConnection("jdbc:h2:~/test", "test", "" );
          Statement stmt = con.createStatement();
          stmt.executeUpdate( "CREATE TABLE table1 ( user varchar(50) )" );
          stmt.executeUpdate( "INSERT INTO table1 ( user ) VALUES ( 'Claudio' )" );
          stmt.executeUpdate( "INSERT INTO table1 ( user ) VALUES ( 'Bernasconi' )" );

          ResultSet rs = stmt.executeQuery("SELECT * FROM table1");
      while( rs.next() )
      {
          String name = rs.getString("user");
          System.out.println( name );
      }
      stmt.close();
      con.close();
    }
    catch( Exception e )
    {
      System.out.println( e.getMessage() );
    }
  }
}

Run it and check the output in the Eclipse Console.
If you additionally want to create a *.jar file for sharing your project to another computer you have to take care that the lib h2*.jar is also exported. The exported jar file will be ca. 1-2 mb. See the following steps below:
Right click on the projects home directory.
Select Export.
Select Runnable Jar file from the Java folder.
Note: If you try to start the exported *.jar on another machine you won’t see any output. Therefore you have to check the home directory for new generated files. If there is a file called like that, everything worked!

H2: Embedded Java DB: Getting Started

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