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# Callback System
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Extensible lifecycle hooks enabling custom logic execution at any point during migration operations, providing comprehensive integration points for auditing, logging, and custom behavior.
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## Capabilities
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### Callback Interface
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```java { .api }
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/**
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 * Callback for receiving notifications before and after each migration.
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 */
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public interface Callback {
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    /** Whether this callback supports the given event and context */
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    boolean supports(Event event, Context context);
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    /** Handle the callback event */
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    void handle(Event event, Context context);
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}
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/**
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 * Base implementation of Callback with convenient defaults
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 */
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public abstract class BaseCallback implements Callback {
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    public boolean supports(Event event, Context context) {
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        return true; // Support all events by default
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    }
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    public abstract void handle(Event event, Context context);
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}
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```
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### Callback Events
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```java { .api }
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/**
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 * Enumeration of all callback events
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 */
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public enum Event {
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    // Migration events
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    BEFORE_MIGRATE, AFTER_MIGRATE, BEFORE_EACH_MIGRATE, AFTER_EACH_MIGRATE,
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    BEFORE_EACH_MIGRATE_STATEMENT, AFTER_EACH_MIGRATE_STATEMENT,
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    // Validation events  
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    BEFORE_VALIDATE, AFTER_VALIDATE,
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    // Clean events
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    BEFORE_CLEAN, AFTER_CLEAN,
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    // Baseline events
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    BEFORE_BASELINE, AFTER_BASELINE,
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    // Repair events
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    BEFORE_REPAIR, AFTER_REPAIR,
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    // Info events
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    BEFORE_INFO, AFTER_INFO,
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    // Undo events
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    BEFORE_UNDO, AFTER_UNDO, BEFORE_EACH_UNDO, AFTER_EACH_UNDO
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}
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```
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### Callback Context
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```java { .api }
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/**
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 * The context relevant to a callback.
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 */
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public interface Context {
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    /** Get the configuration currently in use */
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    Configuration getConfiguration();
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    /** Get the JDBC connection to use to execute statements */
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    Connection getConnection();
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    /** Get info about the migration being executed (when available) */
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    MigrationInfo getMigrationInfo();
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    /** Get the SQL statement being executed (for statement-level events) */
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    Statement getStatement();
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}
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```
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## Usage Examples
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```java
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// Audit callback
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public class AuditCallback extends BaseCallback {
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    @Override
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    public void handle(Event event, Context context) {
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        if (event == Event.AFTER_EACH_MIGRATE) {
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            MigrationInfo info = context.getMigrationInfo();
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            System.out.println("Applied migration: " + info.getVersion() + " - " + info.getDescription());
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        }
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    }
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}
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// Configuration with callbacks
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Flyway flyway = Flyway.configure()
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    .dataSource(dataSource)
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    .callbacks(new AuditCallback(), new LoggingCallback())
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    .load();
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```