关于使用Dom创建xml文档时的问题

[amdey]

我使用xerces中的DOM来创建一个新的xml文档，如下：

Document doc=new DocumentImpl();
创建后的xml文档中默认编码方法为:

<?xml version="1.0" endocing="utf-8"?>

现在我想把utf-8用gb2312替换掉，请问在程序中应该如何处理？

[swinging]

TransformerFactory tFactory = TransformerFactory.newInstance();
Transformer transformer = tFactory.newTransformer();
Properties properties = transformer.getOutputProperties();
properties.setProperty(OutputKeys.ENCODING, "gb2312");//// 就是这句了
properties.setProperty(OutputKeys.METHOD, "xml");
properties.setProperty(OutputKeys.VERSION, "1.0");
properties.setProperty(OutputKeys.INDENT, "no");
transformer.setOutputProperties(properties);

DOMSource source = new DOMSource(doc);

其中最后一句中得doc是拼好得XML。比如：
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.newDocument();
Element root = doc.createElement("DSTreeRoot");
..........................（就不细写了）