To record GWT requests, see Record a test scenario.
To recap, the GWT-RPC protocol allows the exchange of custom Java objects. If the classes are missing for the sent Java objects, the request binary data cannot be decoded for conversion to XML. The following procedure explains how to resolve the problem of missing Java classes.
java.io.Serializable
interface (from GWT 1.5 onwards) or the com.google.gwt.user.client.rpc.IsSerializable
interface (for earlier versions).