1.文档中全为英文,不设置编码,直接写入.

XMLWriter writer = new XMLWriter(new FileWriter("output.xml"));      
writer.write(document);      
writer.close();     

2.文档中含有中文,设置编码格式再写入.

OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("GBK");    // 指定XML编码
XMLWriter writer = new XMLWriter(new FileWriter("output.xml"),format);
writer.write(document);
writer.close();