Esboço de um framework de migração de banco usando java

Migration.java

// TODO ao gerar uma nova versão, criar um ID único da mesma


public interface Migration {
	void up  (Database database) throws MigrationException;
	void down(Database database) throws MigrationException;
	String version();
	String tag();
}

public interface FieldModifier{
}

public class Field implements DatabaseObject{
	public Field(String name, Set<FieldModifier> modifiers){
		// TODO
	}
	
	public Field(String name, FieldModifier... modifiers){
		this(name,new HashSet<FieldModifier>(Arrays.asList(modifiers)));
	}
}

public class Table implements DatabaseObject{

	public Table( String tableName , Set<Field> fields , Set<Index> indexes ) {
	}
	
	public Table( String tableName ){
	}
	
	public Table with(Field... fields){
		setFields(new HashSet<Field>(Arrays.asList(fields)));
		return this;
	}
	
}

public interface Database{
	
	<T> create(T databaseObject);
	<T> execute (T databaseObject);

	void process() throws MigrationException;
	
}

public class DefaultDatabase implements Database{
	
	public List<DatabaseObject> todo = new ArrayList<DatabaseObject>();
	
	public <T extends DatabaseObject> create(T databaseObject){
		todo.append(databaseObject);
		return databaseObject;	
	}

	public <T extends DatabaseOperation> execute(T databaseOperation){
		todo.append(databaseOperation);
		return databaseOperation;
	}
	
}

public final class Definitions {

	public static final Field field(String name, FieldModifier... modifiers){
		return new Field(name,modifiers);
	}

	public static final Insert insert(String table){
		return new Insert(table);
	}
	
	public static final Table table(String name){
		return new Table(name);
	}
	
}

public final class Filter{
	
	public static final Filter eq(String field,Object value){
		return new Filter(field,Operator.EQ,value);
	}

	public static final Filter not(Filter filter){
		return new Filter(null,Operator.NOT,filter);
	}

	public static final Filter isNotNull(String field){
		return new Filter(field,Operator.NOT_NULL,null);
	}

	public static final Filter isNull(String field){
		return new Filter(field,Operator.NULL,null);
	}

	private Field(String field, Operator operator, Object value){
		// TODO
	}
	
}

// imports

public class CreateNewUserTableMigration implements Migration {
	
	public void up(Database database) throws MigrationException{
		
		database.create (table ("user").fields(field("login"   ,Type.STRING,Key.PRIMARY,Key.UNIQUE),
											   field("password",Type.STRING,Check.NOT_NULL        )));
		database.create(field("login",Type.String).on(table("user")));
		database.execute(insert("user").column("login","admin").column("password","admin"));
	
	}
	
	public void down(Database database) throws MigrationException {
		database.execute(delete("user").where(eq("login","admin"));
		database.execute(delete("user").where(eq("login","teste"));
		database.drop(table("user"));		
	}
	
	public String version(){
		// TODO fica a critério definir a versão da migração	
	}
	
	public String tag(){
		// TODO pode criar uma tag que identifique um conjunto de migrations
	}

}