Why would “java.lang.IllegalStateException: The resource configuration is not modifiable in this context.” appear deploying Jersey app?

Question

I have created an app implementing REST services locally using:

Eclipse Indigo Jersey 2.4 Tomcat 7.0.47

When running locally using Eclipse, the services work

Answer 1

The issue in my case is that the shaded jar did not include the javassist package that Jersey uses to do bytecode manipulation. When shading a jar, make sure to include org.javassist:*.

    
        org.javassist
        javassist
        3.26.0-GA