com.marringtons.object
Class Migration

java.lang.Object
  com.marringtons.object.Migration

public class Migration

extends Object

This is the class that performs data migrations used as part of software upgrades. If you have a DAO class that needs to change, you must ensure that databases with instances of that object are correctly migrated. Each package with DAO classes that require migration will have a class called Migrations. This class will have an inner class with the same name as the DAO that needs migrating. Each if these inner classes will have in turn one or more inner classes that define the migration path - one for each change to the object. Personally I name the individual classes after the date (v20050418), but using the release number is equally valid as you will probably only need one per release. This class is a copy of the target DAO before it is altered, with the addition of a Migration.Interface interface. Inner classes can be migrated by creating an inner class path in the Migration path that matches.

Author:

Paul Marrington

Nested Class Summary

static interface

Migration.Interface Interface is used by inner classes of migration classes to define a migrate method used to move to a more recent version of a DAO that has been updated.

Constructor Summary

Migration()

Method Summary

static boolean	database(String dataBaseName) Look at all classes in a database and see which ones have a migration path - then follow it.
static boolean	database(String dataBaseName, String migrationClassName) Look at all classes in a database and see which ones have a migration path - then follow it.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Migration

public Migration()

Method Detail

database

public static boolean database(String dataBaseName)
                        throws IOException

Look at all classes in a database and see which ones have a migration path - then follow it. The result is that all classes will be migrated to the latest version. Run in maintenance mode - when the database has not been used and is not accessable. Usually run by the upgrade installation script for an application package.

Parameters:

dataBaseName - Name of database to find and run through the migration process. Database must be on the data path to be found.

Returns:

true if the database was found.

Throws:

IOException - on physycal disk error retrieving database.

database

public static boolean database(String dataBaseName,
                               String migrationClassName)
                        throws IOException

Look at all classes in a database and see which ones have a migration path - then follow it. The result is that all classes will be migrated to the latest version. Run in maintenance mode - when the database has not been used and is not accessable. Usually run by the upgrade installation script for an application package.

Parameters:

dataBaseName - Name of database to find and run through the migration process. Database must be on the data path to be found.

migrationClassName - Normally a class of Migrations will be looked for for each package that has a class in the database. For junit - and for the odd case when you want a special migration - you can specify the migration class.

Returns:

true if the database was found.

Throws:

IOException - on physycal disk error retrieving database.