Permissions required to create charts with JFreeChart

I'd like to use JFreeChart to create charts from code running under a security manager. This fails with the error message

java.lang.InternalError: Can't connect to window server - not enough permissions.

If I change my policy file to give the code unrestricted permissions, it works fine开发者_StackOverflow, so the error must be due to some permission missing in my policy. But which one? I tried various AWT-related permissions but nothing seems to work. Is there a way to find out which permissions are missing?

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When you start the app , add the following to the jvm arguments - it produces a huge amount of output, but it will point you in the right direction when there are permissions failures.

-Djava.security.debug=access,failure