playing with the AdminClient i tried using a VoldemortFilter with fetchEntries() but any time i provided a non-null reference to my VoldemortFilter on the client i got nothing back and this on the server:

03 23, 2010 04:23:33 AM cc: voldemort.server.protocol.admin.AdminServiceRequestHandler ERROR: handleFetchPartitionEntries failed for request(partitions: 0
partitions: 1
store: "keys"
filter {
  name: "com.audiencescience.service.user.util.VoldemortSingleKeyFilter"
  data: "\312\376\272\276\...\000\036\000!\000\002\000\001\000\"\000\000\000\002\00 0#"

fetch_values: true
)
voldemort.VoldemortException: Failed to load and instantiate the filter class
        at voldemort.server.protocol.admin.AdminServiceRequestHandler.getFilterFromReq uest(AdminServiceRequestHandler.java:656)
        at voldemort.server.protocol.admin.AdminServiceRequestHandler.handleFetchParti tionEntries(AdminServiceRequestHandler.java:159)
        at voldemort.server.protocol.admin.AdminServiceRequestHandler.handleRequest(Ad minServiceRequestHandler.java:114)
        at voldemort.server.socket.SocketServerSession.run(SocketServerSession.java:73 )
...
Caused by: java.lang.ClassNotFoundException: com.audiencescience.service.user.util.VoldemortSingleKeyFilter
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
...
        at voldemort.server.protocol.admin.AdminServiceRequestHandler.getFilterFromReq uest(AdminServiceRequestHandler.java:652)
        ... 6 more

i originally used an anonymous inner class (i wasn't too surprised that didn't work).  
then tried a public static inner class - i could rationalize that not working as well since the outer class wasn't serialized and there might be loading issues.  
but i couldn't figure out the normal public class, with or without Serializable.  

public class VoldemortSingleKeyFilter implements VoldemortFilter {
    private Object _key;
    public VoldemortSingleKeyFilter (Object key) { _key = key; }
    public boolean accept(Object key, Versioned<?> val) {
        return key.equals(_key);
    }

should this feature work?  is there a flag i need to set on the server?  oh, version is 0.70.1 and the connection is between a windows client and a linux server both running Java 1.6 (64-bit 1.6.0_13 on the server; 32-bit 1.6.0_17 on the client).