Yes, you need to define a serializer for each of your beans.  Or rather,
provide a mapping to a bean serializer.  And those beans should use only
Java primitives and/or their related class implementations (like
BigDecimal...and String).  There may be ways to create serializers for more
complex classes like OutputStreams...I've tried, and failed, and then
realized that I could just send byte arrays for character or binary data, so
why bother?

Also, if you create arrays of your beans, then you need to define
serializers for each type of array too.

Incidentally, my only experience is with Axis.  So my answers above are
based on working with Axis.  From what little I understand about the world
of web services in general, I'd say it's far easier to work with than Apache
SOAP.  I thought the latter was just what was available before Axis came
out, and my understanding is that it's quite a bit more complex.  I think
Axis was created to encapsulate a lot of the tedious details.  For instance,
you don't have to worry at all about creating or parsing the actual SOAP
message.  Axis takes care of all of that.

Apache has a fairly decent, though too brief, tutorial.

http://ws.apache.org/axis/java/user-guide.html