Flush readonly map together with shared on SerializerCache.flush()

[vdaniloff]

Without these flushing the cache may be not enough - for example if a new subtype for existing interface is added by a new provider, serialization cache will still return old serializer for an interface.

[cowtowncoder]

I would need to have some kind of indication of an observed problem to change something that seems to have been working for a decade now... :)

That is, without a test I don't think I'd want to merge this.

I am also not sure what the problem would be: subtypes are not really relevant here as the cache is keyed by actual type, not supertype.

[cowtowncoder]

Actually, looking at this again, this makes sense. And while it'd be nice to have tests I don't think they are essential after all.
Merging.

[vdaniloff]

Thanks for merging this.

I am really sorry for late answer, forgot about this. After creating the issue I realized it did not help with my original problem anyway (there was a need to make Jackson rebuild polymorphic serializers, after serializer was used before new subclasses where registered). I fixed that problem by changing application.

The change makes some sense, but flushing serializers may still not work:

1. There a _knownSerializers field in StdSerializerProvider. It is final and if a serializer is already there - it will not be flushed
2. There's anyway no such method for flush deserialisers in provider (only in DeserializerCache itself)

Combined makes me think maybe there's still something to do. I am not sure now what is the purpose of the method - to really make Jackson recreate serializers (potentially with new logic) or just to free memory (maybe then javadoc update is needed).

[cowtowncoder]

@vdaniloff Ok thank you for additional information. I am also not sure how useful this method really is; it generally is better to just create a new ObjectMapper, to be honest (f.ex ObjectMapper.copy()).
Part wrt (Std)SerializerProvider definitely seem to make cache flush operation about useless.

But as to original intent I am pretty sure it's about saving memory and not so much new functionality.