Jersey 1.x is not planned to support JDK 9. Why would you need to use Jersey 1.x with JDK 9, instead of Jersey 2.x?

@jansupol thx for your feedback so far!

As part of neo4j, we have some legacy parts that use jersey 1.x and migrating them to the new version will require end users to update their extension/plugins. It would be nice if we can avoid doing that for some time (on our side we will need major release to change API and env. that much)
to allow some of our users already switch and try java 9.
I agree that keep using jersey 1.x will not gonna work in a long-term, but adding Java 9 to a list of supported platforms will gonna simplify our life a lot and will allow us to progress on updating our sometimes legacy technology stack.

Also of note is that Netflix Eureka uses jersey 1.x by default, and as such the eureka spring cloud starter fails to run on jdk9 due to this. It's not easy (i.e. I haven't found a way, although there may be one that involves a lot of maven dependency overrides--also, not ideal) to configure the eureka spring cloud starter to completely eliminate the jersey 1.x dependency and use the jersey2 fork of eureka instead to run on jdk9.

My opinion is that if the work is already done, and it doesn't break compatibility with jdk8, why not merge it?