title: Global variable in unbind method of OSGi service is null
body: <p>My application is based on OSGi (Equinox). A OSGi service binds another service by defining a Component XML and bind / unbind methods in the appropriate class. </p>
  
  <p>In the unbind method the value of a global String variable (same class like unbind method) should be retrivied.</p>
  
  <p>Strangely the String attribute is null there, although the attribute was definitely set before. What's the reason for that? How can I get the value that I have set?</p>