xstream: custom converter

marshal/unmarshal

private String toXML(Application app) throws Exception {
 XStream xStream = new XStream(new DomDriver());
 xStream.registerConverter(new ApplicationConverter());
 xStream.alias("application", Application.class);
 return xStream.toXML(app);
}

private Application toApplication(String xml) throws Exception {
 XStream xStream = new XStream(new DomDriver());
 xStream.registerConverter(new ApplicationConverter());
 xStream.alias("application", Application.class);
 return (Application) xStream.fromXML(xml);
}

class ApplicationConverter implements Converter {
  private static final String FULLDATE_FORMAT = "dd/MM/yyyy HH:mm:ss";

  /** Marshall xml into application object */
  public void marshal(Object obj, 
      HierarchicalStreamWriter writer, 
      MarshallingContext context) {
    Application app = (Application) obj;
    pushContent(writer, "applicationId", app.getApplicationId());
    DateFormat formatter = new SimpleDateFormat(FULLDATE_FORMAT);
    pushContent(writer, "createdDate", formatter.format(app.getCreatedDate()));
    pushMapContent(writer, app.getFields());
  }

  /** Push content into xml */
  private void pushContent(HierarchicalStreamWriter writer, 
                           String key, Object value) {
    writer.startNode(key);
    writer.setValue(value.toString());
    writer.endNode();
  }

  /** Push map content into xml */
  private void pushMapContent(HierarchicalStreamWriter writer, Map map) {
    Iterator iter = map.keySet().iterator();
    while(iter.hasNext()) {
      String key = (String) iter.next();
      Object value = map.get(key);
      writer.startNode(key);
      if (value instanceof Map) {
        pushMapContent(writer, (Map) value);
      }
      else if (value instanceof String) {
        writer.setValue((String) value);
      }
      writer.endNode();
    }
  }

  /** Unmarshall application into xml   */
  public Object unmarshal(HierarchicalStreamReader reader, 
                          UnmarshallingContext context) {
    Application app = new Application();
    DateFormat formatter = new SimpleDateFormat(FULLDATE_FORMAT);

    while (reader.hasMoreChildren()) {
      reader.moveDown();
      try {
        if ("applicationId".equals(reader.getNodeName())) {
          app.setApplicationId(reader.getValue());
        }
        else if ("createdDate".equals(reader.getNodeName())) {
          app.setCreatedDate(formatter.parse(reader.getValue()));
        }
        else {
          popMapContent(reader, app.getFields());
        }
      }
      catch(ParseException e) {
        LOG.debug("Parsing date for "+reader.getNodeName()+" has failed", e);
      }
      reader.moveUp();
    }
    return app;
  }

  /** Pop xml into map content */
  private void popMapContent(HierarchicalStreamReader reader, 
                             Map map) {
    if (reader.hasMoreChildren()) {
      Map childMap = new TreeMap();
      map.put(reader.getNodeName(), childMap);
      while (reader.hasMoreChildren()) {
        reader.moveDown();
        popMapContent(reader, childMap);
        reader.moveUp();
      }
    }
    else {
      map.put(reader.getNodeName(), reader.getValue());
    }
  }

  public boolean canConvert(Class clazz) {
    return clazz.equals(Application.class);
  }
}