//读取内容
 public void read() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  Element root = document.getRootElement();
  Element book = (Element) root.elements("书").get(1);//获取xml中的第二本书
  String  value = http://www.mamicode.com/book.element("书名").getText();
 }
 //读取属性
 public void readAttr() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  Element root = document.getRootElement();
  Element book = (Element) root.elements("书").get(1);//获取xml中的第二本书
  String value  = book.element("书名").attributeValue("name");
 }
 //添加
 public void add() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  Element book = document.getRootElement().element("书");
  book.addElement("售价").setText("209");
  
  XMLWriter writer = new XMLWriter(new OutputStreamWriter(new FileOutputStream("src/book.xml"),"utf-8"));
  writer.write(document);
  writer.close();
 }
 //向指定位置添加element
 public void add2() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  Element book = document.getRootElement().element("书");
  List list = book.elements();
  
  Element element = DocumentHelper.createElement("售价");
  element.setText("309");
  
  list.add(2, element);
  OutputFormat format = OutputFormat.createPrettyPrint();
  format.setEncoding("utf-8");
  
  XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"), format);
  writer.write(document);
  writer.close();
 }
 //删除
 public void delete() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  Element price = document.getRootElement().element("书").element("售价");
  price.getParent().remove(price);
  OutputFormat format = OutputFormat.createPrettyPrint();
  format.setEncoding("utf-8");
  
  XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"), format);
  writer.write(document);
  writer.close();
 }
 //更新
 public void update() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  Element book = (Element) document.getRootElement().elements("书").get(1);
  book.element("作者").setText("或黎明");
  OutputFormat format = OutputFormat.createPrettyPrint();
  format.setEncoding("utf-8");
  
  XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"), format);
  writer.write(document);
  writer.close();
 }
 //利用xpath提取xml文档中的数据
 public void extract() throws Exception{
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/book.xml");
  
  String value = http://www.mamicode.com/document.selectSingleNode("作者").getText();//得到第一个作者的名字
 }
 //查找user.xml中是否有 和用户相匹配的用户名和密码
 @Test
 public void extract2() throws Exception{
  String userName = "aaa";
  String passWord ="123";
  SAXReader reader = new SAXReader();
  Document document = reader.read("src/users.xml");
  Node node =  document.selectSingleNode("//user[@userName=‘"+userName+"‘ and @passWord=‘"+passWord+"‘]");
  if(node == null){
   System.out.println("登陆失败！");
  }else{
   System.out.println("登陆成功！");
  }
 }