使用 playframework 2.7.3 运行 sbt-proguard 时出现此错误。
[info] Reading program jar [/home/johnny/.ivy2/cache/com.typesafe.akka/akka-stream_2.13/jars/akka-stream_2.13-2.5.23.jar] (filtered)
[error] Error: Can't read [/home/johnny/.ivy2/cache/com.typesafe.akka/akka-stream_2.13/jars/akka-stream_2.13-2.5.23.jar(;;;;;;!META-INF/MANIFEST.MF)] (Can't process class [akka/stream/javadsl/JavaFlowSupport$Flow$1.class] (Unsupported class version number [55.0] (maximum 52.0, Java 1.8)))
[error] java.lang.RuntimeException: Proguard failed with exit code [1]
[error] at scala.sys.package$.error(package.scala:26)
[error] at com.lightbend.sbt.SbtProguard$.runProguard(SbtProguard.scala:114)
[error] at com.lightbend.sbt.SbtProguard$.$anonfun$proguardTask$2(SbtProguard.scala:94)
[error] at sbt.util.FileFunction$.$anonfun$cached$1(FileFunction.scala:73)
[error] at sbt.util.FileFunction$.$anonfun$cached$4(FileFunction.scala:147)
[error] at sbt.util.Difference.apply(Tracked.scala:313)
[error] at sbt.util.Difference.apply(Tracked.scala:293)
[error] at sbt.util.FileFunction$.$anonfun$cached$3(FileFunction.scala:143)
[error] at sbt.util.Difference.apply(Tracked.scala:313)
[error] at sbt.util.Difference.apply(Tracked.scala:288)
[error] at sbt.util.FileFunction$.$anonfun$cached$2(FileFunction.scala:142)
[error] at com.lightbend.sbt.SbtProguard$.$anonfun$proguardTask$1(SbtProguard.scala:98)
[error] at scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:40)
[error] at sbt.std.Transform$$anon$4.work(System.scala:67)
[error] at sbt.Execute.$anonfun$submit$2(Execute.scala:269)
[error] at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] at sbt.Execute.work(Execute.scala:278)
[error] at sbt.Execute.$anonfun$submit$1(Execute.scala:269)
[error] at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] at java.lang.Thread.run(Thread.java:748)
[error] (Proguard / proguard) Proguard failed with exit code [1]
[error] Total time: 2 s, completed Oct 24, 2019 1:32:40 PM
这是说问题--- Unsupported class version number [55.0] (maximum 52.0, Java 1.8)。我怎样才能摆脱这个？