Add support for non-blocking ("async") XML parsing

[sdeleuze]

As a followup of FasterXML/jackson-core#57 which provides JSON (and SMILE) async parsing, it would be great for jackson-dataformat-xml to provide such support as well.

We would like to leverage such support in Spring WebFlux, see SPR-15697 to provide Jackson based XML + JSON support like in Spring MVC.

[cowtowncoder]

Sounds good, in general. Not nearly as easy as with others, due to layering of things, but on plus side there is at least one actual parser (aalto-xml) that could implement this.

[edeandrea]

Hi I just wanted to see if there were any updates on this.

[arisjramos]

Any update on this ? We need it to much!!

[cowtowncoder]

@arisjramos No one is working on this, and I am fairly certain I will not have time to work on this any time soon. So contributions would be welcome.

Note, however, that since non-blocking handling is only implemented at streaming level, but XML module only support databind access, it is not certain there is specific route to make use of such implementation.