You could add an EnumConverter.

public class EnumConverter extends Converter {
public boolean canConvert(Class type) { return type.isEnum(); }

public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { writer.setValue(((Enum)source).name()); }

public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { return Enum.valueOf(context.getRequiredType(), reader.getValue()); }
}

public class EnumConverter extends Converter {
public boolean canConvert(Class type) { return type.isEnum() || Enum.class.isAssignableFrom(type); }

public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { writer.setValue(((Enum)source).name()); }

public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { return Enum.valueOf(context.getRequiredType().getSuperclass(), reader.getValue()); }
}

public class EnumConverter extends Converter {
public boolean canConvert(Class type) { return type.isEnum() || Enum.class.isAssignableFrom(type); }

public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) { writer.setValue(((Enum)source).name()); }

public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { Class c = context.getRequiredType().getSuperclass() == Enum.class ? context.getRequiredType() : context.getRequiredType().getSuperclass(); return Enum.valueOf(c, reader.getValue()); }
}

public class XStreamTest extends TestCase {
private XStream xStream;

protected void setUp() throws Exception { super.setUp(); xStream = new XStream(); xStream.registerConverter(new EnumConverter()); }

public void test() throws Exception { User user = PicapsResourceFactory.getInstance().getUserRegistry().getUser("plantfloor"); assertEquals(user, xStream.fromXML(xStream.toXML(user))); }

public void testEnum() throws Exception { assertEquals(SimpleEnum.Test1, xStream.fromXML(xStream.toXML(SimpleEnum.Test1))); assertSame(SimpleEnum.Test1, xStream.fromXML(xStream.toXML(SimpleEnum.Test1))); assertEquals(AnotherEnum.Test1, xStream.fromXML(xStream.toXML(AnotherEnum.Test1))); assertSame(AnotherEnum.Test1, xStream.fromXML(xStream.toXML(AnotherEnum.Test1))); }

private enum SimpleEnum { Test1, Test2; }

private enum AnotherEnum {
Test1() {
Object getObj() { return new Object(); }
}, Test2() {
Object getObj() { return new Object(); } }
};

abstract Object getObj();
}
}

I have also added EnumMapper that ensures that the polymorphic enums don't get converted into the $1 classes, meaning the XML is cleaner and aliases can be used for enums.

I've credited your work in the code and added you to the contributors page.