Java.DBMigrationTools.Can you use Java code to write Flyway migrations?

✅ Short Answer

Yes, you can write migrations in Java by implementing the JavaMigration interface or extending BaseJavaMigration.
This allows you to write complex, logic-driven database changes in code, including loops, conditional logic, or calling other APIs.

🔍 How to Write a Java-Based Migration

✅ Step 1: Create a class like this:

import org.flywaydb.core.api.migration.BaseJavaMigration;
import org.flywaydb.core.api.migration.Context;

public class V3__Add_default_users extends BaseJavaMigration {
    @Override
    public void migrate(Context context) throws Exception {
        try (var statement = context.getConnection().createStatement()) {
            statement.execute("INSERT INTO users (name, email) VALUES ('admin', 'admin@example.com')");
        }
    }
}

✅ Step 2: Place the file in:

src/main/java/db/migration/

📦 By default, Flyway scans this package:

db.migration

🧠 Java Migration Naming Convention

Type	Naming Format
Versioned	V3__Add_default_users.java
Repeatable	R__Seed_data.java

Same naming rules apply as for SQL files.

✅ When to Use Java Migrations

Use Case	Why Java Helps
Conditional logic	Handle “if exists” / “if not” programmatically
Complex data transformations	Java gives more control than plain SQL
Interacting with external systems	API calls, config checks, auditing
Platform-agnostic logic	Avoid SQL dialect issues

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⚠️ Limitations

• No support for undo migrations in Java
• You still need to track the version and description manually in the class name
• Slightly more setup effort than SQL

📌 Key Takeaways

✅ Flyway supports Java-based migrations for advanced, logic-heavy use cases
✅ Use BaseJavaMigration to create versioned migrations in Java
✅ Name your classes like V2__Description.java and place them under db.migration
✅ Ideal when SQL is not expressive or safe enough for your migration logic