Hello,
I posted the same question in Atlassian forum. Then I solved it by myself but I want to know now if am I doing something wrong with dependencies.
I created a standalone application using docx4j and all was working.
Then I needed to insert in into Jira and I created my plugin.
After some environment problems (I had to exclude xml-apis) to let the plugin start, I had problems in context declaration: It was ...