DualCrud
DualCrud is a persistence utility that allows you to offer a meta instance of a persistence service to its client (for example: a business service). This is especially useful if you want to perform on the fly migration of data models.
Consider following, classical structure:
Now, if you want to migrate this structure to jpa (*Repository) in running system, without downtime, you could construct following DC Structure:
... and you are done 
Btw: The components in green are provided by the library.
DualCrud supports following pre-configured modes
Name | Effect |
|---|---|
migrateOnTheFly | whenever an item on left persistence is accessed it is migrated to the right persistance. |
migrateBackOnTheFly | same as migrateBackOnTheFly but in reverse direction. |
migrateOnCallOnly | only explicit calls to migrate will trigger data movement from left to right. |
migrateBackOnCallOnly | same as migrateOnCallOnly but in reverse direction. |
duplicate | read from left but write to both. Useable if you want to have a failover copy. |
useLeftOnly | Use only left persistence. |
useRightOnly | Use only right persistence. |
To create one of the above modes use static factory methods in net.anotheria.anoprise.dualcrud.DualCrudConfig
DualCrud Config properties
The static factory methods in DualCrud configs create broad-purpose configs. However, if the one you're looking for is not there, you can create your own config by setting the properties in the config object directly.
Name | Effect |
|---|---|
migrationDirection | direction in which the data should be migrated |
readFromBoth | if true after the primary persistence is asked for a data, and returned null or throwed exception, secondary persistence is asked |
migrateOnRead | If true and a migration direction is specified, reading from old persistence will cause a migration. |
writeToBoth | If true, the service will write to both peristences. |
deleteUponMigration | If true upon a successful migration the old copy will be deleted. |
migrateOnWrite | If true and a migration direction is specified, writing is only allowed to new persistence. Items on 'old' persistence are migrated to new on write. |