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java.lang.NullPointerException when exporting view

Hey all,
I'm getting an error when trying to export a visualization from ProM6, please see the attached stack trace for details.
I'm no Java buff, so not entirely sure what might be happening here, but looks like a bug in the FreeHEP library. Please note that I'm running ProM6 on Java 1.8.0_77-b03 on Ubuntu 14.04LTS (just updated from Java 7 to make sure this wasn't the cause).
The error appears similar to what is described here:;wap2
The 'Browse' button in the 'Export view as...' dialog doesn't do anything and the (presumably) file type dropdown selection is disabled (greyed out). Clicking 'OK' results in the error.
Not the end of the world, as all the visualizations are still rendered properly inside of ProM, but a bit annoying for note-taking, so I'd love to hear from anyone who's had the same problem, or any suggestions for possible fixes.



  • Dear djr,

    As far as I know, there are two possible explanations for this:
    1. ProM cannot find the freehep libraries included.
    2. ProM finds the wrong freehep libraries.
    The latter happened to me when upgrading to a new set of freehep libraries. For the moment, however, I assume your problem is more related to the former.

    Which version of ProM are you running? Lately, we moved these libraries from the ProM framework into one of the ProM packages (Widgets, to be precise). Possibly, on your system, ProM now cannot find these libraries. Could be because they are not in the classpath, or something like that.

    Kind regards,


  • djr
    edited March 2016
    Hey Eric,
    Thanks for the quick answer!
    I'm running the most recent release version, i.e. PROM_VERSION = 6.5.1.
    My ProM651_lib directory contains a bunch of freehep-* .jars, most of which seem to be on version 2.1.1 (although freehep-io, which appears a likely culprit here, is on 2.0.2)., which builds the classpath, looks ok at first glance. I'll fiddle around with it and post back here, if I manage to fix it.

    Thanks again, Cheers! 

  • Hi,

    The version 2.0.2 for freehep-io is okay (that is, it works for us...), even when (almost) all others are at 2.1.1. That does not seem to be a problem. And I guess all freehep libraries end up in the classpath, right?

    The freehep-export library seems unable to find the others, as this export library should load the others. But what then the problem is?

    Sorry that I cannot be of more help here...


  • Dear Eric,

    I have a related issue to this Thread, which is why I'm posting here. The whole widgets-library is not included in the checkout from the repository and I don't know where I can get it from.

    As a result the freehep libraries are missing too, hence I get compiling errors and can not start coding.

    Can you help me with this issue?

    Thank you very much,

  • Dear Oliver,

    That's correct. Only the ProM framework is installed by the installer. Typically, when ProM starts for the first time, it will install the necessary packages, which includes Widgets.

    If ProM fails to install these packages, please run the ProM Package Manager first and install the default (RunnerUpPackages) package. This should install all required packages, including Widgets. Afterwards, start ProM, which should then find the packages.


  • Thank you a lot :)
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