Failed when starting Spark 1.5.0 standalone cluster

[Netwaver]

Hi Spark experts,
                         I am trying to migrate my Spark cluster from 1.4.1 to 
latest 1.5.0 , but meet below issues when run start-all.sh script.

                          Exception in thread "main" 
java.lang.NoClassDefFoundError: org/apache/spark/launcher/Main
Caused by: java.lang.ClassNotFoundException: org.apache.spark.launcher.Main
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: org.apache.spark.launcher.Main.  Program will 
exit.

                        I could easily migrate Spark cluster from 1.3.1 to 
1.4.1 on the same machines before, I am wondering if Spark 1.5.0 asks for some 
special jars in the classpath?
       I am using JDK 1.6 , don't know if 1.6 is also supported by Spark 1.5.0. 
Any suggestion will be highly appreciated, thank you all.