Spring Boot pretty much dominates. I think Play market share is a bit more in the long tail of alternatives. Also, it's very Scala centric and not widely used without Scala.

Spring is increasingly Kotlin centric and the combination is pretty nice. There's a wide variety of other frameworks such as vert.x, ktor, quarcus, etc. They are popular but compared to Spring quite niche.

With Graal and Kotlin native, the whole space is becoming less JVM centric as well. E.g. Spring Native just went into beta and Ktor has been inching closer to working on the Kotlin Native compiler for a while now (still some missing pieces). Particularly for serverless, this is relevant due to reduced startup time. Overall performance is not significantly better though.

You have Grails p. P p a Rails alternative, I don't recommend it though Grails has come a long way but still has a lot of inconeniences and is becoming obsolete by the day, it became a monster with tangled and twisted code, everything (views, models, queries) has 2 or 3 reimplementations that don't quite work and are not finished. I used to develop more than 5 services in it and frankly I don't know how I managed to stay sane or sleep at night

Spring (Boot) is the biggest.

After that, in terms of being standard and widely-used, Java EE, now known as Jakarta EE. It has a comparable level of magic to Spring Boot; maybe some of it is done better, some of it isn't.

DropWizard is still going.

I suspect that a larger proportion of Java programmers are working on headless data-munging backend apps than, say, Ruby or Node programmers. Those kinds of apps often either don't need a framework at all, or need some more specialist framework. Hence, Rails-esque frameworks are less of a priority for the Java community as a whole. Which is a bit of a shame, because it would be great to have a really strong alternative to Spring.

I keep using JEE, or one of the Java CMS for more complex stuff, like Liferay or Adobe Experience Manager.

However Quarkus and Micronaut are also quite appealing for small projects.

Check out https://www.jhipster.tech

It uses Spring Boot, but comes with a lot of sane defaults.

Job listings in the searches I am subscribed to are almost universally Spring and Spring Boot.

Java backend = Spring Boot. It dominates the market.