How to convert XML to java.util.Map and vice versa

Question

I'm searching a lightweight API (preferable single class) to convert a

Map<String,String> map = new HashMap<String,String();

to xml and, vice versa, convert the XML back to a Map.

example:

Map<String,String> map = new HashMap<String,String();
map.put("name","chris");
map.put("island","faranga");

MagicAPI.toXML(map,"root");

result:

<root>
  <name>chris</chris>
  <island>faranga</island>
</root>

and back:

Map<String,String> map = MagicAPI.fromXML("...");

I dont want to use JAXB or JSON conversion API. It doesnt have to take care of nested maps or attributes or anything else, just that simple case. Any suggestions?

---

Edit: I created a working copy & paste sample. Thanks to fvu and Michal Bernhard.

Download latest XStream framework, 'core only' is enough.

Map<String,Object> map = new HashMap<String,Object>();
map.put("name","chris");
map.put("island","faranga");

// convert to XML
XStream xStream = new XStream(new DomDriver());
xStream.alias("map", java.util.Map.class);
String xml = xStream.toXML(map);

// from XML, convert back to map
Map<String,Object> map2 = (Map<String,Object>) xStream.fromXML(xml);

No converters or anything else is required. Just the xstream-x.y.z.jar is enough.

Answer 1

You could build something yourself quite easily, here's a first start. Note that some things are missing; you should escape characters like < and > in the root, keys and values and take proper care of character encodings; you'll have to add that yourself.

public class MagicAPI {
    public static String toXML(Map<String, String> map, String root) {
        StringBuilder sb = new StringBuilder("<");
        sb.append(root);
        sb.append(">");

        for (Map.Entry<String, String> e : map.entrySet()) {
            sb.append("<");
            sb.append(e.getKey());
            sb.append(">");

            sb.append(e.getValue());

            sb.append("</");
            sb.append(e.getKey());
            sb.append(">");
        }

        sb.append("</");
        sb.append(root);
        sb.append(">");

        return sb.toString();
    }
}

Answer 2

How about XStream? Not 1 class but 2 jars for many use cases including yours, very simple to use yet quite powerful.

Answer 3

One option would be to roll your own. It would be fairly simple to do:

Document doc = getDocument();
Element root = doc.createElement(rootName);
doc.appendChild(root);
for (Map.Entry<String,String> element : map.entrySet() ) {
    Element e = doc.createElement(element.getKey());
    e.setTextContent(element.getValue());
    root.appendChild(e);
}
save(doc, file);

and the load is an equally simply getChildNodes and a loop. Sure it has a bit of boiler plate that the XML Gods demand but it is at most 1 hours work.

Or you could look at Properties if you are not too fused about the format of the XML.

Answer 4

XStream!

public class Test {

    public static void main(String[] args) {

        Map<String,String> map = new HashMap<String,String>();
        map.put("name","chris");
        map.put("island","faranga");

        XStream magicApi = new XStream();
        magicApi.alias("root", Map.class);
        magicApi.registerConverter(new MapEntryConverter());

        String xml = magicApi.toXML(map);
        System.out.println("Result of tweaked XStream toXml()");
        System.out.println(xml);


    }

    public static class MapEntryConverter implements Converter {

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

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

            AbstractMap map = (AbstractMap) value;
            for (Object obj : map.entrySet()) {
                Entry entry = (Entry) obj;
                writer.startNode(entry.getKey().toString());
                writer.setValue(entry.getValue().toString());
                writer.endNode();
            }
        }

        public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
            // dunno, read manual and do it yourself ;)
        }

    }

}