JVM Instrumentation Agent: What is the purpose of SplunkClassFileTransformer and its functionality?

[shirbal]

I am trying to understand the need for SplunkClassFileTransformer class and its functionality. Can someone explain me the usage / purpose of SplunkClassFileTransformer?
I am not sure I understand the need for it

[Damien_Dallimor]

Javadocs : https://docs.oracle.com/javase/7/docs/api/java/lang/instrument/ClassFileTransformer.html

In the Agent code , the class transformer implementation is loaded here : https://github.com/damiendallimore/SplunkJavaAgent/blob/master/src/com/splunk/javaagent/SplunkJavaAg...

[shirbal]

But why do we need to transform the classes?

[Damien_Dallimor]

To add tracing instructions into your code AFTER it has been compiled into bytecode :
http://www.correlsense.com/java-bytecode-instrumentation-an-introduction/