J2ME Pattern: RMS Migrations

Inspired by RoR Migrations I’ll summarize how to gain similar benefits in the J2ME world with respect to it’s special needs:

  • attach a version marker to each RecordStore name,
  • as there’s no callback at install time and at launch time things must be quick as possible, use a fall-back mechanism on opening RecordStores,
  • therefore use a custom method to open RecordStores and give it a handler for RecordStoreNotFoundException,
  • use methods rather than classes to implement migrations,
  • only migrate forward,
  • hardcode the migration methods into the RecordStoreNotFoundException handler – there’s no Reflection in J2ME.

=>

  • you can change the RMS store names and storage byte semantics whenever you like without the fear of breaking anything,
  • there’s impact on startup time only if the storage semantics changed and needs to be converted,
  • you don’t add myriads of classes over time,
  • you need to write a converter method for each version bump of each store.

Check back later for sample code.

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