How to test a REST service that uses JWT in SoapUI?

I've found a semi-automatic way to keep a valid JWT token across TestCases without losing too much time, using an external file containing the token.

1. Have an external tool generating a valid JWT token into a file.

2. Open your project in SoapUI and add a jwt variable with the value ${=new File('/path/to/token_file.txt').text}

3. In your requests, reference your variable as a JWT header with the value ${#Project#jwt}

When the token expire, just relaunch the generator script, and SoapUI will automatically load the new token.