Jackson question... why does this fail?

[Mike Oxford]

        <dataFormats>
            <json id="jack" library="Jackson"/>
        </dataFormats>
...
        <route id="myRoute">
            <from ref="listener" />           // mina component
            <unmarshal ref="jack" />       // unmarshal it
            <marshal ref="jack" />          // marshal it
        </route>

I can put a bean:myBean in between and see that, yes, it is being
unmarshalled correctly.  Even more complex JSON will unmarshall correctly,
and I can traverse the returned Map.

{"a":5}             // input
[B@73207f36  // output

Why does the <marshal/> call return crap (an object ref of some kind?) even
for simple calls?

Thanks,

-mox