log4j:ERROR Could not find value for key log4j.appender.WARN

log4j:ERROR Could not instantiate appender named "WARN".

Exception in thread "main" java.lang.NoClassDefFoundError: org/eclipse/jetty/server/SessionManager

at com.jfinal.core.JFinal.start(JFinal.java:168)

at com.javen.common.APPConfig.main(APPConfig.java:201)

Caused by: java.lang.ClassNotFoundException: org.eclipse.jetty.server.SessionManager

at java.net.URLClassLoader.findClass(URLClassLoader.java:381)

at java.lang.ClassLoader.loadClass(ClassLoader.java:424)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:338)

at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

... 2 more

运行main方法就报这个错，之前项目好好的！