Compilier Version not changing to JDK7

Hello,

I am getting the following error when I try to run my program:

program runs ok for several methods then:

Exception in thread "Thread-2" java.lang.UnsupportedClassVersionError: org.apache/cxf/configuration/jsse/TLSClientParameters :  unsupported major.minor version 52.0

I understand this points to me having compiled with Java8 and trying to run it on Java7. However the program only throws this fault when I get to the code relating to TLS.

I have set the Project Settings > Project SDK to 1.7 and Project Settings > Project Language Level > 7-Diamonds, ARM etc.

I am using gradle and mu build.gradle has 

sourceCompatibility = 1.7

Is there something else I need to do to force 1.7?

Thanks

AG