Nicolas Fränkel recently published the surprising post "A hard look at the state of Java modularization." In that post, Fränkel provides the results of his investigation into support available in the 29 libraries referenced in the blog post "20 popular Java libraries" for modules introduced with JDK 9. Fränkel's investigation aimed to identify which of these popular Java libraries was "modularized" (fully implemented module defined in module-info.java) or provided at least an "automatic module name" via MANIFEST.MF even if the library isn't modularized.
Of the 29 popular Java libraries investigated, Fränkel identified only two (SLF4J 1.8.0-beta2 and JAXB 2.3.1) that are fully modularized. Of the remaining 27 libraries that are not fully modularized, 12 do have an automatic module name defined. That means, of course, that 15 of the 29 libraries (just over 50 percent) do not have any explicit support for modularity introduced with JDK 9!