怎样将生成的xml文件进行格式化

public static void main(String[] args) {
        Document document = DocumentHelper.createDocument();
        Element bookStore = document.addElement("bookStore");

        Element book = bookStore.addElement("book");
        book.addAttribute("category", "e-sport");

        Element title = book.addElement("title");
        title.addText("全职高手");
        Element author = book.addElement("author");
        author.addText("蝴蝶蓝");
        // 设置格式
        OutputFormat format = OutputFormat.createPrettyPrint();
        format.setEncoding("utf-8");
        File file = new File("D:\\图纸\\books.xml");

        XMLWriter writer = null;
        // 设置是否转义  默认为true

        try {
            writer = new XMLWriter(new FileOutputStream(file), format);
            writer.setEscapeText(false);
            writer.write(document);
            writer.close();
        } catch (IOException e) {
            System.out.println("生成文件的时候出现错误："+e);
        }

    }

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

<bookStore>
  <book category="e-sport">
    <title>全职高手</title>
    <author>蝴蝶蓝</author>
  </book>
</bookStore>