XML语言学习5--DOM4J解析+xpath

最新推荐文章于 2025-02-21 09:15:36 发布

原创最新推荐文章于 2025-02-21 09:15:36 发布 · 392 阅读

0 ·

CC 4.0 BY-SA版权

个人学习专栏收录该内容

28 篇文章

订阅专栏

Dom4j是一个简单、灵活的开放源代码的库。Dom4j是由早期开发JDOM的人分离出来而后独立开发的。与JDOM不同的是，dom4j使用接口和抽象基类，虽然Dom4j的API相对要复杂一些，但它提供了比JDOM更好的灵活性。
Dom4j是一个非常优秀的Java XML API，具有性能优异、功能强大和极易使用的特点。现在很多软件采用的Dom4j，例如Hibernate，包括sun公司自己的JAXM也用了Dom4j。

使用Dom4j开发，需下载dom4j相应的jar文件。

开放源代码使用技巧：docs->index.html->quick start

<span style="white-space:pre">	</span>SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));
        Element root = document.getRootElement();

查询标签：

    @Test
    public void read() throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));
        Element root = document.getRootElement();
        List list = root.elements("书");
        Element book = (Element)list.get(1);
        Element book_name = book.element("书名");
        System.out.println(book_name.getText());
    }

查询属性：

//    <书 name="yyyyyyy">
    @Test
    public void readAttribute() throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));
        Element root = document.getRootElement();
        String value = root.element("书").attributeValue("name");
        System.out.println(value);
    }

增加节点：

//    增加售价节点
    @Test
    public void add() throws DocumentException, IOException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));

        Element price = DocumentHelper.createElement("售价");
        price.setText("19元");

        document.getRootElement().element("书").add(price);

        OutputFormat format = OutputFormat.createPrettyPrint();

        XMLWriter writer = new XMLWriter(new FileOutputStream("src/book1.xml"),format);
        writer.write(document);
        writer.close();
    }

修改：

//    修改： <售价>109</售价>
    @Test
    public void update() throws IOException, DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));

        Element price = (Element) document.getRootElement().element("书").elements("售价").get(1);
        price.setText("209");

        OutputFormat format = OutputFormat.createPrettyPrint();

        XMLWriter writer = new XMLWriter(new FileOutputStream("src/book1.xml"),format);
        writer.write(document);
        writer.close();
    }

删除：

//   删除节点<售价>109</售价>
    @Test
    public void delete() throws DocumentException, IOException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));

        Element price = (Element) document.getRootElement().element("书").elements("售价").get(0);
        price.getParent().remove(price);

        OutputFormat format = OutputFormat.createPrettyPrint();

        XMLWriter writer = new XMLWriter(new FileOutputStream("src/book1.xml"),format);
        writer.write(document);
        writer.close();
    }

指定节点的插入：

 //    向指定位置增加售价节点
    @Test
    public void add2() throws DocumentException, IOException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));

        Element price = DocumentHelper.createElement("售价");
        price.setText("19元");

        List list = document.getRootElement().element("书").elements();
        list.add(1,price);

        OutputFormat format = OutputFormat.createPrettyPrint();

        XMLWriter writer = new XMLWriter(new FileOutputStream("src/book1.xml"),format);
        writer.write(document);
        writer.close();
    }

xPath的使用：

查找某一节点：

    @Test
    public void findWithXpath() throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/book1.xml"));

        Element name = (Element) document.selectNodes("//书名").get(1);
        System.out.println(name.getText());
    }

实例：

 @Test
    public void findUsers() throws DocumentException, IOException {

       /* BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("请输入用户名：");
        String username = br.readLine();
        System.out.print("请输入密码：");
        String password = br.readLine();*/
        String username = "aaa";
        String password = "123";
        SAXReader reader = new SAXReader();
        Document document = reader.read(new File("src/users.xml"));

        Element e = (Element) document.selectSingleNode("//user[@username='" + username + "' and @password='" + password + "']");
        if (e != null){
            System.out.println("登陆成功!");
        }else{
            System.out.println("用户不存在或密码错误！");
        }