No, Jetty 9 required Java 7, since the api servlet (servlet 3.1) required Java 7. Although 9.0 could theoretically work on Java 6, we decided that 9 would be servlet 3.1, and only before 9.1 did we make the api servlet switch .. which was mainly due to synchronization problems more than anything.
[update] Jetty 9.2.x is Java 7, and Jetty 9.3.x requires Java 8. This is largely due to support for the HTTP / 2 protocol, which Jetty 9.3.x does ... at peak.
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