spring boot starter jetty requires alpn on JDK12

[Jovons]

According to Jetty official website, it does not need alpn dependency when JDK version is above 9. However, when I started it, it throws the following exception:

org.springframework.context.ApplicationContextException: Unable to start reactive web server; nested exception is java.lang.IllegalStateException: The 'org.eclipse.jetty:jetty-alpn-server' dependency is required for HTTP/2 support.
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:81) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:543) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:66) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at com.my.App.main(App.java:17) ~[classes/:na]
Caused by: java.lang.IllegalStateException: The 'org.eclipse.jetty:jetty-alpn-server' dependency is required for HTTP/2 support.
	at org.springframework.util.Assert.state(Assert.java:94) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.boot.web.embedded.jetty.SslServerCustomizer.createServerConnector(SslServerCustomizer.java:95) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.embedded.jetty.SslServerCustomizer.createConnector(SslServerCustomizer.java:84) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.embedded.jetty.SslServerCustomizer.customize(SslServerCustomizer.java:73) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory.customizeSsl(JettyReactiveWebServerFactory.java:229) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory.createJettyServer(JettyReactiveWebServerFactory.java:181) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.embedded.jetty.JettyReactiveWebServerFactory.getWebServer(JettyReactiveWebServerFactory.java:105) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext$ServerManager.<init>(ReactiveWebServerApplicationContext.java:196) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext$ServerManager.get(ReactiveWebServerApplicationContext.java:213) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.createWebServer(ReactiveWebServerApplicationContext.java:88) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:78) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	... 8 common frames omitted

It is OpenJDK 12.

[wilkinsona]

Thanks for the report but I believe that Jetty does require the ALPN dependency to be on the classpath even when using JDK 9 or later. Their documentation on ALPN states the following:

When using JDK 9 or later and Jetty embedded, the ALPN service implementation is provided by the jetty-alpn-java-client and jetty-alpn-java-server artifacts, respectively for client usage and server usage, and must be added to the classpath.

[RUBenGAMArrarodRiguEZ-ToMtOm]

It should work now with JDK8u252+, JDK9+ and onwards.
See #22188 (comment)