Flyway or Liquibase in Micronaut for DB Migrations

When building real-world applications, database schema changes are unavoidable.
Manual DDL changes or relying on Hibernate’s auto schema generation (hbm2ddl.auto) is risky for production.

✅ Solution: Use Database Migration Tools like Flyway or Liquibase in Micronaut.

Micronaut fully supports two of the most popular tools:

• Flyway
• Liquibase

Both tools:

• Version your database schema.
• Apply migrations automatically.
• Work across all supported databases (H2, PostgreSQL, MySQL, etc).
• Integrate beautifully with Micronaut.

🔧 Why Use Migration Tools?

🚀 Option 1: Flyway Integration

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🔨 Adding Flyway Dependency

For Maven:

    io.micronaut.flyway
    micronaut-flyway

✅ Micronaut will auto-discover Flyway and run migrations at startup.

🔨 Flyway Configuration

Add to application.yml:

flyway:
  datasources:
    default:
      enabled: true

You can configure multiple datasources if needed.

🔨 Create Migration Files

By default, Flyway expects migration files inside:

src/main/resources/db/migration/

Sample Migration: V1__create_students.sql

CREATE TABLE students (
  id BIGINT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(255) NOT NULL,
  date_of_birth DATE,
  email VARCHAR(255)
);

✅ The filename format V<version>__<description>.sql is important!

🔨 Flyway Run Flow

When Micronaut starts:

• Flyway scans existing migrations.
• Runs any pending migrations.
• Ensures schema is up-to-date.

🔨 Verify Flyway Execution

You’ll see logs like:

Successfully validated 1 migration (execution time 00:00.012s)
Current version of schema: 1
Schema version 1 is up to date. No migration necessary.

✅ Flyway maintains a flyway_schema_history table to track applied migrations.

🚀 Option 2: Liquibase Integration

🔨 Adding Liquibase Dependency

For Maven:

    io.micronaut.liquibase
    micronaut-liquibase

✅ Like Flyway, Micronaut automatically configures Liquibase at startup.

🔨 Liquibase Configuration

Add to application.yml:

liquibase:
  datasources:
    default:
      enabled: true

🔨 Create changelog XML

By default, Liquibase expects changelogs in:

src/main/resources/db/liquibase/

Sample Master Changelog: db-changelog.xml

🔨 Liquibase Run Flow

• Liquibase reads the changelog XML.
• Applies changes not yet applied.
• Tracks changes in DATABASECHANGELOG table.

✅ Like Flyway, it’s fully versioned.

⚖ Flyway vs Liquibase

✅ Both are excellent; pick based on your team’s comfort level.

🐞 Common Migration Errors

🔐 Best Practices for Production

✅ Always run migrations before app starts (CI/CD).
✅ Use version control for migration files.
✅ Never modify applied migrations — create new versions for changes.
✅ Test migrations on staging before production.

🌐 External References

• Micronaut Flyway Guide
• Micronaut Liquibase Guide
• Flyway Docs
• Liquibase Docs

✅ Summary

• ✅ Flyway and Liquibase manage your DB schema versions.
• ✅ Micronaut integrates with both seamlessly.
• ✅ Pick Flyway for simplicity, Liquibase for complex migrations.
• ✅ Never rely on hbm2ddl.auto for production.