Believe that this is quite severe bug unless I did something very wrong.
When sending/rretrieving a Map over XMLRPC the datatype is not correct. I've only checked for the keys, but the error might exist for the values as well.

Provided is a simple unit test to illustrate the bug. To reproduce run the unit tests in SerializationTest.
It has two test methods:
 
 1) one that calls a static method and
 2) and another that calls a method over XMLRPC which in turns call the same static method

The latter fails with a ClassCastException. Instead of the key being the expected Integer it is a String.


>From Console:
[...]
key: 21
value: twentyone
21 -> 'twentyone'
key: 1
value: one
1 -> 'one'
[...]
key: 21

>From Debug -> Variables (in Eclipse):

entry HashMap$Entry<K,V> (id=13)
key "21"
count 2
hash 1599
offset 0
value char[2] (id=27)
value "twentyone"
count 9
hash 0
offset 0
value char[9] (id=29)

As you can see 21 is a char[2] and not an integer as expected.