chapter22-service : error 500 when calling getAllBooks / json

FAIL (Error 500) : 

<pre>
    curl -X GET -H "Accept: application/json" http://localhost:8080/chapter22-service-1.0/rs/book -v
</pre>


WIN : 

<pre>
    curl -X GET -H "Accept: application/xml" http://localhost:8080/chapter22-service-1.0/rs/book -v
</pre>


Tested with GlassFish Server Open Source Edition  4.0  (build 64)
