public static String join(Map map1, Map map2, String delimiter) {
		HashSet keys = new HashSet(map1.keySet());
		keys.addAll(map2.keySet());
		StringBuilder sb = new StringBuilder();
		sb.append("{");
		for (Object key : keys) {
			if (sb.length() > 1) {
				sb.append(",");
			}
			sb.append(key).append("=");
			Object v1 = map1.get(key);
			Object v2 = map2.get(key);
			if (v1!=null) {
				sb.append(v1);
			}
			sb.append(delimiter);
			if (v2!=null) {
				sb.append(v2);
			}
		}
		sb.append("}");
		return sb.toString();
	}