Upgrade Axon 2 to Axon 4

Hello all,

Been having issues upgrading our services from Axon 2 to Axon 4, was wondering if there was a guide or documentation on that, or even the breaking changes from Axon 2 to Axon 3. Saw some threads on this and stack/Github but nothing definitive. Does anyone here have guidance on how to go about this or have official resources for this? I saw that there was a migration guide on the backlog but have yet to see that document.


Hi Paul,

We have had more direct contact on this already, but for continuity on this thread I’ll respond again.

As far as migration guides go, we do have some documentation lying around.
None of these are however documented to a level that we feel it’s fit for the Reference Guide (just yet).
Hence, this information cannot be found there at the moment.

I did take the liberty to answer two distinct StackOverflow question regarding an Axon 2 to 3 migration, which you can find here and here.
Additionally, the root directory of Axon Framework release 4.x contains an API-Changes file, which contains all the important bits to be able to migrate from Axon 3 to 4.

Concluding though, as pointed out, none of these are written down in a format that they’re workable for the Reference Guide at this stage.
Regardless, I hope this helps you out Paul, as well as other readers of this forum!