Java H2 Database Tutorial

In this tutorial, we will learn how to do database programming in H2 with Java.

H2 Database Overview

H2 is an open-source lightweight Java database. It can be embedded in Java applications or run in the client-server mode. Mainly, H2 database can be configured to run as an in-memory database, which means that data will not persist on the disk. Because of an embedded database, it is not used for production development but mostly used for development and testing.
This database can be used in embedded mode or in server mode. Following are the main features of the H2 database −
  • Extremely fast, open-source, JDBC API
  • Available in embedded and server modes; in-memory databases
  • Browser-based Console application
  • Small footprint − Around 1.5MB jar file size

Features of H2 Database

The main features of the H2 Database are as follows −
  • It is an extremely fast database engine.
  • H2 is open source and written in Java.
  • It supports standard SQL and JDBC API. It can use PostgreSQL ODBC driver too.
  • It has embedded and Server mode.
  • H2 supports clustering and multi-version concurrency.
  • It has strong security features.

H2 Database - Installation

Refer below link to install the H2 database: 

Java H2 Database CRUD Examples

Let's develop Java programs to create a JDBC connection with the H2 database and the CRUD(Create, Retrieve, Update and Delete) operations with the H2 database. These CRUD operations are equivalent to the CREATE, SELECT, UPDATE and DELETE statements in SQL language.

H2 Database Setup and Configuration

  1. Download H2 database dependency or jar file from official website http://www.h2database.com/html/download.html or from https://mvnrepository.com/artifact/com.h2database/h2/1.4.199.
  2. Add H2 Jar file to your project classpath.
  3. By default the Java application to connect to an H2 in-memory store with the username sa and an empty password.
 private static String jdbcURL = "jdbc:h2:~/test";
 private static String jdbcUsername = "sa";
 private static String jdbcPassword = "";

JDBC Util Class

Let's first create an H2JDBCUtils.java file with all JDBC common methods like:
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class H2JDBCUtils {

    private static String jdbcURL = "jdbc:h2:~/test";
    private static String jdbcUsername = "sa";
    private static String jdbcPassword = "";

    public static Connection getConnection() {
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(jdbcURL, jdbcUsername, jdbcPassword);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return connection;
    }

    public static void printSQLException(SQLException ex) {
        for (Throwable e: ex) {
            if (e instanceof SQLException) {
                e.printStackTrace(System.err);
                System.err.println("SQLState: " + ((SQLException) e).getSQLState());
                System.err.println("Error Code: " + ((SQLException) e).getErrorCode());
                System.err.println("Message: " + e.getMessage());
                Throwable t = ex.getCause();
                while (t != null) {
                    System.out.println("Cause: " + t);
                    t = t.getCause();
                }
            }
        }
    }
}
This class we will use in the next Java programs.

1. Create a Table with the H2 Database

This Java program creates a users table into the H2 database.
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * Create Statement JDBC Example
 * @author Ramesh Fadatare
 *
 */
public class H2CreateExample {

    private static final String createTableSQL = "create table users (\r\n" + "  id  int(3) primary key,\r\n" +
        "  name varchar(20),\r\n" + "  email varchar(20),\r\n" + "  country varchar(20),\r\n" +
        "  password varchar(20)\r\n" + "  );";

    public static void main(String[] argv) throws SQLException {
        H2CreateExample createTableExample = new H2CreateExample();
        createTableExample.createTable();
    }

    public void createTable() throws SQLException {

        System.out.println(createTableSQL);
        // Step 1: Establishing a Connection
        try (Connection connection = H2JDBCUtils.getConnection();
            // Step 2:Create a statement using connection object
            Statement statement = connection.createStatement();) {

            // Step 3: Execute the query or update query
            statement.execute(createTableSQL);

        } catch (SQLException e) {
            // print SQL exception information
            H2JDBCUtils.printSQLException(e);
        }
    }
}
Output:
create table users (
  id  int(3) primary key,
  name varchar(20),
  email varchar(20),
  country varchar(20),
  password varchar(20)
  );

2. Insert Record into Table with H2 Database

The below Java program insert a single record in users table of H2 database.
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * Insert PrepareStatement JDBC Example
 * 
 * @author Ramesh Fadatare
 *
 */
public class H2InsertExample {
    private static final String INSERT_USERS_SQL = "INSERT INTO users" +
        "  (id, name, email, country, password) VALUES " +
        " (?, ?, ?, ?, ?);";

    public static void main(String[] argv) throws SQLException {
        H2InsertExample createTableExample = new H2InsertExample();
        createTableExample.insertRecord();
    }

    public void insertRecord() throws SQLException {
        System.out.println(INSERT_USERS_SQL);
        // Step 1: Establishing a Connection
        try (Connection connection = H2JDBCUtils.getConnection();
            // Step 2:Create a statement using connection object
            PreparedStatement preparedStatement = connection.prepareStatement(INSERT_USERS_SQL)) {
            preparedStatement.setInt(1, 1);
            preparedStatement.setString(2, "Tony");
            preparedStatement.setString(3, "tony@gmail.com");
            preparedStatement.setString(4, "US");
            preparedStatement.setString(5, "secret");

            System.out.println(preparedStatement);
            // Step 3: Execute the query or update query
            preparedStatement.executeUpdate();
        } catch (SQLException e) {

            // print SQL exception information
            H2JDBCUtils.printSQLException(e);
        }

        // Step 4: try-with-resource statement will auto close the connection.
    }
}
Output:

INSERT INTO users  (id, name, email, country, password) VALUES  (?, ?, ?, ?, ?);
prep0: INSERT INTO users  (id, name, email, country, password) 
VALUES  (?, ?, ?, ?, ?); {1: 1, 2: 'Tony', 3: 'tony@gmail.com', 4: 'US', 5: 'secret'}

3. Read Record with H2 Database

This Java program read record from the users table.
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

/**
 * Select PreparedStatement JDBC Example
 * 
 * @author Ramesh Fadatare
 *
 */
public class H2SelectExample {
    private static final String QUERY = "select id,name,email,country,password from users where id =?";

    public static void main(String[] args) {

        // using try-with-resources to avoid closing resources (boiler plate code)

        // Step 1: Establishing a Connection
        try (Connection connection = H2JDBCUtils.getConnection();

            // Step 2:Create a statement using connection object
            PreparedStatement preparedStatement = connection.prepareStatement(QUERY);) {
            preparedStatement.setInt(1, 1);
            System.out.println(preparedStatement);
            // Step 3: Execute the query or update query
            ResultSet rs = preparedStatement.executeQuery();

            // Step 4: Process the ResultSet object.
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                String email = rs.getString("email");
                String country = rs.getString("country");
                String password = rs.getString("password");
                System.out.println(id + "," + name + "," + email + "," + country + "," + password);
            }
        } catch (SQLException e) {
            H2JDBCUtils.printSQLException(e);
        }
        // Step 4: try-with-resource statement will auto close the connection.
    }
}
Output:
prep0: select id,name,email,country,password from users where id =? {1: 1}
1,Tony,tony@gmail.com,US,secret

4. Update Record with H2 Database

This Java program updates a single record in the users table.
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

/**
 * Update PreparedStatement JDBC Example
 * @author Ramesh Fadatare
 *
 */
public class H2UpdateExample {

    private static final String UPDATE_USERS_SQL = "update users set name = ? where id = ?;";

    public static void main(String[] argv) throws SQLException {
        H2UpdateExample updateStatementExample = new H2UpdateExample();
        updateStatementExample.updateRecord();
    }

    public void updateRecord() throws SQLException {
        System.out.println(UPDATE_USERS_SQL);
        // Step 1: Establishing a Connection
        try (Connection connection = H2JDBCUtils.getConnection();
            // Step 2:Create a statement using connection object
            PreparedStatement preparedStatement = connection.prepareStatement(UPDATE_USERS_SQL)) {
            preparedStatement.setString(1, "Ram");
            preparedStatement.setInt(2, 1);

            // Step 3: Execute the query or update query
            preparedStatement.executeUpdate();
        } catch (SQLException e) {

            // print SQL exception information
            H2JDBCUtils.printSQLException(e);
        }

        // Step 4: try-with-resource statement will auto close the connection.
    }
}
Output:
update users set name = ? where id = ?;

5. Delete Record with H2 Database

This Java program deletes a particular record from users table in the H2 database.
package net.javaguides.jdbc.h2.crud;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

public class H2DeleteExample {
    private static final String deleteTableSQL = "delete from users where id = 1";

    public static void main(String[] argv) throws SQLException {
        H2DeleteExample deleteExample = new H2DeleteExample();
        deleteExample.deleteRecord();
    }

    public void deleteRecord() throws SQLException {

        System.out.println(deleteTableSQL);
        // Step 1: Establishing a Connection
        try (Connection connection = H2JDBCUtils.getConnection();
            // Step 2:Create a statement using connection object
            Statement statement = connection.createStatement();) {

            // Step 3: Execute the query or update query
            statement.execute(deleteTableSQL);

        } catch (SQLException e) {
            // print SQL exception information
            H2JDBCUtils.printSQLException(e);
        }
    }
}
Get source code of this tutorial on my GitHub Repository.


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