需要dom4j的jar包

Document doc = saxReader.read(new ByteArrayInputStream(fileString.getBytes()));
//            Element rootElement = doc.getRootElement();
            
            OutputFormat format = OutputFormat.createPrettyPrint();
            format.setEncoding("utf-8");
            XMLWriter writer = new XMLWriter(new FileWriter(outFile),format);
            writer.write(doc);
            writer.close();