How to disable pretty-printing(white space/newline) in XStream?

Thanks, your posts helped!!! Here is what I use to convert to a String.

String strXML = "";
XStream xs = new XStream();
StringWriter sw = new StringWriter();
xs.marshal(this,  new CompactWriter(sw));
strXML = sw.toString();

With some help from the community, I've figured out the answer.

For XML you have to change the way how you serialize:

The line:

xStream.toXML(o, new OutputStreamWriter(stream, encoding));

changed to line

xStream.marshal(o, new CompactWriter(new OutputStreamWriter(stream, encoding)));

For JSON you only change the way how the XStream is created. So the initialization of the XStream is changed to:

private final XStream xstreamOut = new XStream(new JsonHierarchicalStreamDriver() {
    public HierarchicalStreamWriter createWriter(Writer writer) {
        return new JsonWriter(writer, new char[0], "", JsonWriter.DROP_ROOT_MODE);
    }
});

Note that the 4-parameter JsonWriter constructor is used.

Use the marschal method on xstream with a compact writer

xstream.marshal(someObject, new CompactWriter(out));