Hi Vijay,
I offer basic trouble shooting help with this, but have you traced the pipeline and made sure you are handing the :convertToString method a proper value?
I spent a day working on this error with this method, and the method I was using before this was bad, and therefore I was not actually handing the :convertToString method any string value, hence the “out of bounds”
If this is the answer, it makes your life easier!
Let me know if this helps, Good Luck,
Scott Corder
#webMethods#Integration-Server-and-ESB#Adapters-and-E-Standards