PayPal-Java-SDK & Google App Engine - Subscription Reflection Error

I am trying to create a PayPal Subscription on Google App Engine using the PayPal-Java-SDK. I have a slight variation of the code in this link implemented, but I am getting the exception below when calling the Plan.update after creating the PATCH object.

java.lang.SecurityException: java.lang.IllegalAccessException: Reflection is not allowed on protected java.lang.String java.net.HttpURLConnection.method