jetty配置SSL的问题？？？？

我现在正打算使用jetty，但是配置SSL的时候在启动时就会报
java.lang.ClassNotFoundException: org.eclipse.jetty.server.nio.SelectChannelConnector in file:/D:/jetty-distribution-9.3.8.v20160314/jetty-distribution-9.3.8.v20160314/etc/jetty.xml
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.jetty.start.Main.invokeMain(Main.java:214)
at org.eclipse.jetty.start.Main.start(Main.java:457)
at org.eclipse.jetty.start.Main.main(Main.java:75)
Caused by: java.lang.ClassNotFoundException: org.eclipse.jetty.server.nio.SelectChannelConnector
有知道什么原因呢吗？