jdk 1.6 tomcat-redis session clustering Error

[qwg5061]

when I work with java6 and tomcat 7 it came through
java.lang.UnsupportedClassVersionError: com/radiadesign/catalina/session/RedisSessionHandlerValve : Unsupported major.minor version 51.0。
how can i fix it

I am using jdk1.6 and tomcat 7. jedis2.2.0 commons-pool 1.6 and tomcat-redis-session-manager 1.2-tomcat7
The following syntax was added to "context.xml"

but This kind of error occurred.
java.lang.UnsupportedClassVersionError: com/radiadesign/catalina/session/RedisSessionHandlerValve : Unsupported major.minor version 51.0。

Do you have the correct syntax for jdk 1.6?
how can i fix it