Overview

This plugin provides an opinionated way of using Flyway, for your SQL database migrations.

Database migration (also known as database evolution) is the process of upgrading the schema of a database in a predictable and replayable way.

The migration approach this plugin provides:

  • Is based on plain Java classes (no ".sql" text files).
  • Allows full dependency injection support in those migration classes.
  • Makes sure the connection provided by Flyway, to run the migration, is going to be used by any direct or indirect requests made to the database.

Usage

Writing migration classes

You use standard Java classes to define the migrations to be executed. By doing do, you use Java code and you have access to any libraries you need.

Location

The migrations classes targetting a specific DataSource must all be located under the same package, and their names must follow some rules. Here's an example of some migration classes for a "mainDb" DataSource:

As you can see in this example, all the migrations classes for the main database are located in the same package ("com.widgets.app.migrations.maindb").

Migration class

A migration class extends SpincastFlywayMigrationBase. You simply have to implement the runMigration(...) method in order to specify the queries to run:

public class M_2017_04_01_01__Security_tables extends SpincastFlywayMigrationBase {

    @Inject
    public M_2017_04_01_01__Security_tables(@MainDataSource DataSource dataSource,
                                            JdbcUtils jdbcUtils) {
        super(dataSource, jdbcUtils);
    }

    @Override
    protected void runMigration(Connection connection) {

        createPermissionsTables(connection);
        createRolesTables(connection);
        //...  
    }
    
    //...
}

Explanation :

  • 1 : The migration class extends SpincastFlywayMigrationBase and follows the naming convention.
  • 3-7 : In the constructor, you inject anything you need to run this migration and you provide the base class with its own dependencies. The most important one being the DataSource to target.
  • 9-15 : You implement the runMigration(...) method. This method receives the connection to use to run your SQL queries. In this method, you can directly write and execute some SQL queries or you can call some existing repositories to do it.

Naming convention

The name of a migration class must follow some rules:

  • It must start with "M_" ("M" is for "migration").
  • The part after the "M_" represents the version of the migration. Here you can use different formats, but you must stay consistent! We suggest two kinds of formats:
    • Date based: for example "2017_04_01_01". Here, the date is "2017-04-01" and it would be the first migration of the day. Another migration executed on the same day would be named "2017_04_01_02".
    • Semantic versioning: for example "12_0_3" or "2_1_37_1". This would follow the standard Semantic Versioning.
  • Finally, you can add an optional third part to the name, by prefixing it with double backslashes: "M_2017_04_01_01__Security_tables". The "__" and everything coming after it will be ignored. This allows you to add a description and make the name more meaningful.

The migrations classes are executed in order, based on the versions extracted from their names... Make sure you keep a consistent naming convention!

Indirect requests work too!

By extending SpincastFlywayMigrationBase, the connection provided by Flyway to run the migration is going to be used to run all SQL requests, both directly and indirectly, as long as you use the scopes provided by the Spincast JDBC plugin.

For example, let's say one of the steps in your migration is to add a new column to your users table. You may already have a UserService providing a updateUsers(...) method... It would be nice to be able to reuse the logic provided by that service to update your existing users with a custom value, once the new column is added! But Since the createUser(...) method doesn't accept any Connection parameter, and may itself call a UserRepository component, how could the SQL request being performed in the end use the proper connection provided by Flyway?

The answer is that a specificConnection scope has been created in the base class, and your migration code (direct and indirect) is all ran inside of it!

Creating the migration context

The second step to set up your migrations is to create a migration context, the component by which a migration is actually started. In this context, you specify the DataSource to be migrated and where to find the migration classes to execute.

To create such context, you inject the SpincastFlywayFactory component and you call the createMigrationContext() method. Using the created context, you then execute the migration:

@Inject
SpincastFlywayFactory factory;

SpincastFlywayMigrationContext migrationContext =
                    factory().createMigrationContext(myMainDataSource,
                                                     "public",
                                                     M_2018_01_01_01.class.getPackage().getName());
migrationContext.migrate();

Explanation :

  • 5 : You specify the target DataSource to be migrated.
  • 6 : The schema to target. This schema is not always required if the default schema is used. But it depends on the database you are using, and it is a good habit to specify it.
  • 7 : The package where the migrations classes to execute are located. Note that, like in this example, you can use one of the class from the package to get its name.
  • 8 : When the context is created, you execute it. This starts the migration...

Your migrations should probably be executed as soon as your application starts (using an init method, for example). The plugin will detect any migration classes which haven't been applied yet and will use them.

Dependencies

The Spincast Flyway Utils plugin depends on the Spincast JDBC plugin, a plugin which is not provided by default by the spincast-default package. This dependency plugin will be automatically installed, you don't need to install it by yourself in your application (but you can).

Just don't be surprised if you see transitive dependencies being added to your application!

Installation

1. Add this Maven artifact to your project:

<dependency>
    <groupId>org.spincast</groupId>
    <artifactId>spincast-plugins-flyway-utils</artifactId>
    <version>0.9.52</version>
</dependency>

2. Add an instance of the SpincastFlywayUtilsPlugin plugin to your Spincast Bootstrapper:


Spincast.configure()
        .plugin(new SpincastFlywayUtilsPlugin())
        // ...