Hive.execution.engine

Hi,
I have set hive.execution.engine=spark;
and try to execute a query , its giving me an error and hive session get ended.
with below error

Caused by: java.lang.ClassNotFoundException: org.apache.spark.SparkConf
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

Could you please do the needful.