JavaLite - cassandra migrations

The DBMigrator plugin also allows (since v 2.4.x) working with Cassandra databases.

Since Cassandra is not really a relation database, it is not currently supported by ActiveJDBC models. However, the DBMigrator does provide Cassandra support to create/drop keyspaces as well as make all necessary changes for tables, etc, as long as you provide CQL - compatible code in your migration files.

Migration file extensions are sql, not cql.

JDBC Driver

The JavaLite DBMigrator plugin uses its own JDBC driver developed strictly to add Cassandra support to the plugin.

The JDBC driver is NOT a real JDBC driver. Its implementation strictly supports the DBMigrator plugin and nothing else. Using this driver outside the DBMigrator plugin might cause bodily injury.

Example configuration

<plugin>
    <groupId>org.javalite</groupId>
    <artifactId>db-migrator-maven-plugin</artifactId>
    <version>2.4-j8</version>
    <configuration>
        <configFile>src/main/resources/database.properties</configFile>
        <environments>development</environments>
        <createSql>CREATE KEYSPACE %s WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1 };</createSql>
        <dropSql>DROP KEYSPACE IF EXISTS %s</dropSql>
    </configuration>
    <executions>
        <execution>
            <id>create_keyspace</id>
            <phase>validate</phase>
            <goals>
                <goal>create</goal>
            </goals>
        </execution>
        <execution>
            <id>migrate</id>
            <phase>validate</phase>
            <goals>
                <goal>migrate</goal>
            </goals>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupId>com.datastax.oss</groupId>
            <artifactId>java-driver-core-shaded</artifactId>
            <version>4.8.0</version>
        </dependency>
    </dependencies>
</plugin>

Line 6 points to a database.properties for development environment as is typical for JavaLite projects.
Lines 8 and 9 include create and drop statements to assist the plugin

The database.properties file includes this content:

development.driver=org.javalite.cassandra.jdbc.CassandraJDBCDriver
development.url=jdbc:cassandra:///javalite?config_file=src/application.conf

The JDBC URL

The general format of a URL is:

jdbc:cassandra:///[keyspace]?config_file=[path/to/config/file]

As you can see, the host is not provided. If you do provide the host, it will result in an error.

Real example:

jdbc:cassandra:///javalite?config_file=src/application.conf

The keyspace in an example above is javalite.

The URL merely serves as a pointer to a Cassandra configuration file, which might include quite elaborate configuration for Cassandra, including multiple hosts.

Here is an example of an application.conf file:

datastax-java-driver {
  basic.contact-points = [ "127.0.0.1:9043" ]
}

For more information on the format of this file, refer to: Cassandra Java Driver Configuration.

Multiple databases example

Often you have Cassandra as well as another relational database

First, define properties for driver and the URL:

    <properties>
        <cassandra.driver>org.javalite.cassandra.jdbc.CassandraJDBCDriver</cassandra.driver>
        <cassandra.url>jdbc:cassandra:///javalite?config_file=${project.basedir}/src/application.conf</cassandra.url>
    </properties>

The add this plugin to your POM file:

<plugin>
    <groupId>org.javalite</groupId>
    <artifactId>db-migrator-maven-plugin</artifactId>
    <version>2.5-j8-SNAPSHOT</version>
    <configuration>
        <createSql>CREATE KEYSPACE %s WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};</createSql>
        <dropSql>DROP KEYSPACE IF EXISTS %s</dropSql>
    </configuration>
    <executions>
        <execution>
            <id>cassandra_create</id>
            <configuration>
                <driver>${cassandra.driver}</driver>
                <url>${cassandra.url}</url>
                <createSql>CREATE KEYSPACE %s WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1 };</createSql>
            </configuration>
            <phase>validate</phase>
            <goals>
                <goal>create</goal>
            </goals>
        </execution>
        <execution>
            <id>cassandra_migrate</id>
            <configuration>
                <driver>${cassandra.driver}</driver>
                <url>${cassandra.url}</url>
            </configuration>
            <phase>validate</phase>
            <goals>
                <goal>migrate</goal>
            </goals>
        </execution>
        <execution>
            <id>mysql_migrations</id>
            <configuration>
                <migrationsPath>src/migrations/mysql</migrationsPath>
                <driver>com.mysql.cj.jdbc.Driver</driver>
                <url>jdbc:mysql://localhost/test_project</url>
                <username>activejdbc</username>
                <password>****</password>
            </configuration>
            <phase>validate</phase>
            <goals>
                <goal>migrate</goal>
            </goals>
        </execution>
    </executions>
    <dependencies>
        <dependency>
            <groupId>com.datastax.oss</groupId>
            <artifactId>java-driver-core-shaded</artifactId>
            <version>4.8.0</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.16</version>
        </dependency>
    </dependencies>
</plugin>

The configuration above will migrate both, Cassandra as well as MySQL database.

As you can see, Cassandra and MySQL have different executions. Use those execution names when you create new migrations or perform any other operations:

For example, this command:

mvn db-migrator:new@cassandra_create -Dname=create_table_students

Will result in this output:

[INFO] --- db-migrator-maven-plugin:2.4-j8:new (cassandra_create) @ db-migrator-maven-plugin-test2 ---
[INFO] Created new migration: ***/src/test/project/cassandra-mysql-test-project/src/migrations/20201006125327_create_table_students.sql

By default migrationsPath points to src/migrations.

The actual migrations will be triggered by a Maven validate phase, which happens at the beginning of any Maven build.

Working examples

Check out complete working examples of Cassandra Maven Projects.

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Cassandra migrations