How to convert a Map to an XML

Question

I have a HashMap that I would like convert into an XML file. This tutorial demonstrates how to do this with XStream, and it works wonderfully. However, in my case, I do not need to unmarshall the XML to a Map. Therefore the unmarshal method becomes superflous. Is there another way in XStream to accomplish what I want to do without implementing the unmarshall method. Or is there another friendly Object to XML api that I can use to accomplish this ?

Answer 1

I decided to extends a MapConverter and override its marshal method:

 public static class MapEntryConverter extends MapConverter {

public MapEntryConverter(Mapper mapper) {
    super(mapper);     
}

public boolean canConvert(Class clazz) {
    return ListMultimap.class.isAssignableFrom(clazz);
}

public void marshal(Object value, HierarchicalStreamWriter writer,
    MarshallingContext context) {

    ListMultimap<String, String> map = (ListMultimap<String, String>) value;
    for (String key : map.keys()) {
    writer.startNode(key);
    writer.setValue(map.get(key).get(0));
    writer.endNode();
    }
}


}

And I use this converter when I marshall my map:

    ListMultimap<String, String> multimap = LinkedListMultimap.create();
multimap.put("x", "1");
multimap.put("x", "2");
multimap.put("y", "3");

XStream xStream = new XStream(new DomDriver());
xStream.registerConverter(new MapEntryConverter(xStream.getMapper()));

xStream.alias("add", multimap.getClass());
String xml = xStream.toXML(multimap);
System.out.println(xml);