How to send Dynamic request payload , in nested json using objectmapper , jsonnode , objectNode ? Getting null pointer exception

Question

enter image description here System.out.println("=======================This is objnd ============================"); System.out.println(objnd); ==================================================================================== OUTPUT ERROR --------------------- --------------PRINTING THE JSON STRING..----------------------------------- {"isbn":"123-456-222","author":[{"lastname":"Doe","firstname":"Jane"}]}

WE ARE GOING ITERATE AND INSERTING THE VALUE.. ----------------------------------- isbn--:Exception in thread "main" java.lang.NullPointerException at dynamically_passingRequestPayload.Dynamically_UpdatingNestedJson_insideJsonArray.traverse(Dynamically_UpdatingNestedJson_insideJsonArray.java:90) at dynamically_passingRequestPayload.Dynamically_UpdatingNestedJson_insideJsonArray.main(Dynamically_UpdatingNestedJson_insideJsonArray.java:67)

SCREEN SHOT----------------------------------------------------------------------------

enter image description here

THE LINE MARKED IN RED COLOUR AM GETTING NULL POINTER EXCEPTION.. KINDLY SOME ONE HELP ME HERE

I debugged the code, and found the key and values passing as parameters.. But not sure y am facing the issue..