A field is not transient when marshaled, then it
is changed to transient, and the unmarshaled
action will unserialize the field.

For example:

public class TryXstream {
    private String tmpFiled = "just a string";
}

It is marshaled into
<org.simon.payment.TryXstream>
  <tmpFiled>just a string</tmpFiled>
</org.simon.payment.TryXstream>

and change the field to transient


public class TryXstream {
    private transient String tmpFiled = "another string";
}

then unmarshal from the xml, the tmpField will be set to "just a string"