The error message seems to indicate there were some problems when the system application __JWSappclients was originally deployed (the generated xml files were not generated in their expected directory).
The system applications got autodeployed the first time a fresh installed domain is started. You can go to the beginning of the server.log to see if there is any error message related to __JWSappclients deployment.
If you do not use java web start technology to access your application, it is probably fine as it won't need to use the _JWSappclients system application. However, the reason which caused problems in this system application deployment might cause problems in other system applications as well. So it's good to figure out the reason..
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