DDL with MariaDB Connector/R2DBC (Spring Data)

Overview

Java developers can use MariaDB Connector/R2DBC to connect to MariaDB database products using the Reactive Relational Database Connectivity (R2DBC) API. R2DBC operations are non-blocking, which makes it more scalable than Java's standard JDBC API. MariaDB Connector/R2DBC can be used with the very popular Spring Data framework, which can provide support for repositories, object mapping, and transaction management.

DDL Operations

DDL (Data Definition Language) refers to all SQL-schema statements in the SQL standard (ISO/IEC 9075-2:2016).

Some examples of DDL include ALTER TABLE, CREATE TABLE, DROP TABLE, CREATE DATABASE, and TRUNCATE TABLE.

With Spring Data, DDL operations can be performed by invoking the following methods:

Code Example: CREATE TABLE

CREATE TABLE is a DDL (Data Definition Language) operation that creates a new table.

Complete the Setup for Examples and Create the Entity class before using the example.

The following example shows how to execute a CREATE TABLE statement:

// Module Imports
import org.mariadb.r2dbc.MariadbConnectionConfiguration;
import org.mariadb.r2dbc.MariadbConnectionFactory;
import org.springframework.data.r2dbc.core.DatabaseClient;

import reactor.test.StepVerifier;

// Main Application Class
public class App {

   // Connection Configuration
   private static MariadbConnectionConfiguration conf;
   private static MariadbConnectionFactory connFactory;
   private static DatabaseClient client;

   // Main Process
   public static void main(String[] args) {

      try {
         // Configure the Connection
         conf = MariadbConnectionConfiguration.builder()
              .host("192.0.2.1").port(3306)
              .username("db_user").password("db_user_password")
              .database("test").build();

         // Instantiate a Connection Factory
         connFactory = new MariadbConnectionFactory(conf);

         // Instantiate a Database Client
         client = DatabaseClient.create(connFactory);

         // Create a Database Table

         client.execute("CREATE OR REPLACE TABLE test.contact" + "(id INT PRIMARY KEY AUTO_INCREMENT,"
               + "first_name VARCHAR(25)," + "last_name VARCHAR(25)," + "email VARCHAR(25)) ENGINE=InnoDB")
               .fetch()
               .rowsUpdated()
               .as(StepVerifier::create)
               .expectNextCount(1)
               .verifyComplete();

      } catch (IllegalArgumentException e) {
         e.printStackTrace();
      } catch (io.r2dbc.spi.R2dbcNonTransientResourceException e) {
         e.printStackTrace();
      } finally {

      }
   }
}

After running the application App, verify the table has been created:

SHOW TABLES;

+----------------+
| Tables_in_test |
+----------------+
| contact        |
+----------------+

DESC contact;

+------------+-------------+------+-----+--------------------------+
| Field      | Type        | Null | Key | Default  | Extra         |
+------------+-------------+------+-----+----------+---------------+
| id         | int(11)     | NO   | PRI | NULL     | auto_increment|
| first_Name | varchar(25) | YES  |     | NULL     |               |
| last_Name  | varchar(25) | YES  |     | NULL     |               |
| email      | varchar(25) | YES  |     | NULL     |               |
+------------+-------------+------+-----+----------+---------------+

Code Example: TRUNCATE TABLE

The following code example truncates the test.contact table created above.

TRUNCATE is a DDL (Data Definition Language) operation that deletes all data from an existing table and resets the AUTO_INCREMENT column counter to 0:

// Module Imports
import org.mariadb.r2dbc.MariadbConnectionConfiguration;
import org.mariadb.r2dbc.MariadbConnectionFactory;
import org.springframework.data.r2dbc.core.DatabaseClient;

import reactor.test.StepVerifier;

// Main Application Class
public class App {
   // Connection Configuration
   private static MariadbConnectionConfiguration conf;
   private static MariadbConnectionFactory connFactory;
   private static DatabaseClient client;

   // Main Process
   public static void main(String[] args) {
      try {
         // Configure the Connection
         conf = MariadbConnectionConfiguration.builder()
              .host("192.0.2.1").port(3306)
              .username("db_user").password("db_user_password")
              .database("test").build();

         // Instantiate a Connection Factory
         connFactory = new MariadbConnectionFactory(conf);

         // Instantiate a Database Client
         client = DatabaseClient.create(connFactory);

         // Truncate Database Table

         client.execute("TRUNCATE TABLE test.contact").fetch()
               .rowsUpdated().as(StepVerifier::create).expectNextCount(1).verifyComplete();
      } catch (IllegalArgumentException e) {
         e.printStackTrace();
      } catch (io.r2dbc.spi.R2dbcNonTransientResourceException e) {
         e.printStackTrace();
      } finally {
      }
   }

}

• A connection factory is used to create an instance of DatabaseClient to connect to the database.
• The DROP and CREATE privileges are needed to truncate a table as TRUNCATE is a DDL statement that drops the table and creates a new table with the same table definition, in effect deleting all data.