Ecplipe Plugin Activation/Classloading

Hi all,

I am trying to deploy a KNIME Extension from a project that I have not previously worked on. It builds fine in eclipse, but when I generate the update site, the extension fails to load with a bunch of identical errors, one for each node, saying that the factor class could not be loaded because the corresponding plugin bundle could not be activated. I haven’t been able to find any sensible (to me) hints on the web. Does anyone here have any experience with this issue? It is likely that this extension hasn’t been deployed in a couple years, so maybe something in KNIME changed in this time?



Hi @Aaron_Hart,

I have seen errors like this many times, it is most likely an issue with the plugin configuration, this error sounds like there is something off in the configuration which prevents the activation.
Can you share the code with us, so I can take a look? Also, try connecting to the running KNIME AP installation using remote debugging (, and setting a breakpoint in the activator of your plugin. Then you can observe any occurring errors.


A few suggestions:

  1. Do you have everything needed included in the file (e.g. any custom lib folders)?
  2. Have you dug around within the built update site to see what is missing compared to your project?
  3. Do you have all dependencies included in the dependencies tab? I’ve been caught once or twice by this with a dependency which happened to always have loaded first when launching KNIME from the SDK / Eclipse, and then not when included in the deployed desktop.
  4. Does the version of the plugin end with .qualifier, e.g. 1.2.34.qualifier? If not KNIME will never figure that you have built a new, updated version of the plugin with whatever changes/fixes were required, and not install the new version over the old.


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Hi Folks,

Thanks for the hints. I was eventually able to track the error down to some conflicting compiler settings. It wasn’t very straightforward to find a meaningful message regarding the problem, but as a hint to future folks, using the feature export wizard gave more detailed error logs than the update site builder.