XML文档读取-DOM

2023-08-14 13:24:46

DOM(Document Object Model)，“文档对象模型”早期是为了解决不用浏览器间数据兼容问题提出的解决方案，现在已经是W3C组织推荐的处理可扩展标志语言的标准编程接口。

W3C DOM 被分为 3 个不同的部分/级别（parts / levels）：

  • 核心 DOM：用于任何结构化文档
  • XML DOM：用于 XML 文档的标准模型
  • HTML DOM：用于 HTML 文档的标准模型

XML DOM 是：

  • 用于 XML 的标准对象模型
  • 用于 XML 的标准编程接口
  • 中立于平台和语言
  • W3C 的标准

SUN公司的JAXP（Java API for XML Processing）提供了对dom的支持；

其解析步骤为：

  • 创建 DOM 解析器的工厂
  • 得到 DOM 解析器对象。

对整个XML文档进行操作

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

<!-- <!DOCTYPE books SYSTEM "books.dtd"> -->

<books>

    <book>

        <author>joy</author>

        <title>java core</title>

        <price>100</price>

    </book>

    <book>

        <author>joy1</author>

        <title>Thinking in java</title>

        <price>100</price>

    </book>

    <book>

        <comment author="joy" id="S001" language="Chinese" price="20" title="Java"/>

        <comment author="joy" id="S002" language="Chinese" price="20" title="Thinking in Java"/>

    </book>

</books>
package com.sy;

import java.io.File;

import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerConfigurationException;

import javax.xml.transform.TransformerException;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.TransformerFactoryConfigurationError;

import javax.xml.transform.dom.DOMSource;

import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

public class first {

    private static void findElement() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("books.xml"));

        NodeList list = doc.getElementsByTagName("title");

        Node node = list.item(1);

        System.out.println(node.getTextContent());

    }

    // 获取属性内容

    private static void getAttribute() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("books.xml"));

        Element node = (Element) doc.getElementsByTagName("comment").item(1);

        System.out.println(node.getAttribute("title"));

    }

    // 使用递归遍历xml文档

    private static void loopNode() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("books.xml"));

        loop(doc);

    }

    private static void loop(Node doc) {

        NodeList list = doc.getChildNodes();

        for (int i = 0; i < list.getLength(); i++) {

            Node node = list.item(i);

            System.out.println(node.getNodeName());

            loop(node);

        }

    }

    // 添加节点，内容，属性

    private static void createElement() throws ParserConfigurationException,

            SAXException, IOException, TransformerFactoryConfigurationError,

            TransformerConfigurationException, TransformerException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("books.xml"));

        // 创建结点

        Element e = doc.createElement("language");

        // 添加内容

        e.setTextContent("Chinese");

        // 添加属性

        e.setAttribute("aa", "xxx");

        // 获取父节点，并append新创建的结点

        doc.getElementsByTagName("book").item(1).appendChild(e);

        // 使用Transformer将内存中更新过的xml文档写入实际的xml文档中

        TransformerFactory tfactory = TransformerFactory.newInstance();

        Transformer tf = tfactory.newTransformer();

        tf.transform(new DOMSource(doc),

                new StreamResult(new File("books.xml")));

    }

    // 注意：DOM的解析方式为将整个xml文档都加载入内存，因此对文档节点的添加、删除和修改操作都是只针对内存中的document对象，因此还需要使用Transformer类将修改真正写入到xml文件中！

    // 删除节点

    private static void deleteElement() throws ParserConfigurationException,

            SAXException, IOException, TransformerFactoryConfigurationError,

            TransformerConfigurationException, TransformerException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("books.xml"));

        // 得到待删除的结点

        Element e = (Element) doc.getElementsByTagName("language").item(0);

        // 获取结点的父节点，然后删除该子结点

        e.getParentNode().removeChild(e);

        // 使用Transformer将内存中更新过的xml文档写入实际的xml文档中

        TransformerFactory tfactory = TransformerFactory.newInstance();

        Transformer tf = tfactory.newTransformer();

        tf.transform(new DOMSource(doc),

                new StreamResult(new File("books.xml")));

    }

    public static void main(String[] args) throws ParserConfigurationException,

            SAXException, IOException, TransformerConfigurationException,

            TransformerFactoryConfigurationError, TransformerException {

        // findElement();

        // getAttribute();

        // loopNode() ;

        // createElement();

        deleteElement();

    }

}

代码解读

这个类内含七个函数（包括五个自定义功能函数，一个递归函数体，一个main函数）

XML文档读取-DOM

五个功能函数：

JfindElement()：发现节点（输出特定节点的文本内容）

    private static void JfindElement() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();// ????

        DocumentBuilder builder = factory.newDocumentBuilder();// ????

        Document doc = builder.parse(new File("./WebRoot/xml/t6.xml"));// 获取页面

        NodeList list = doc.getElementsByTagName("title");// 获取tittle节点

        System.out.println(list.getLength());// 输出title节点长度

        Node node = list.item(1);// 第二个节点

        System.out.println(node.getTextContent());// 输出第二个节点的文本信息

    }

getAttribute()：获得属性值（输出特定节点的属性值）

private static void getAttribute() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("./WebRoot/xml/t6.xml"));

        Element node = (Element) doc.getElementsByTagName("comment").item(1);// 获取comment节点集合

        System.out.println(node.getAttribute("title"));// 输出node节点的tittle属性的值

    }

loop(Node doc)：递归主函数体

private static void loop(Node doc)// Document继承自Node，，，此处为向上转型

    {

        NodeList list = doc.getChildNodes();// 获取孩子节点的集合

        // 便利孩子节点集合

        // 输出每个节点的标签名

        // 递归调用，输出每一层的子节点

        for (int i = 0; i < list.getLength(); i++) {

            Node node = list.item(i);

            System.out.println(node.getNodeName());

            loop(node);

        }

    }
loopNode()递归输出所有节点
// 输出所有节点的节点名称

    private static void loopNode() throws ParserConfigurationException,

            SAXException, IOException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("./WebRoot/xml/t6.xml"));

        loop(doc);// 函数调用输出doc所有子孙节点

    }

createElement()：

创建新节点

把新节点添加到父节点后面

更新文档(把修改后的xml文档同步到本地)

private static void createElement() throws ParserConfigurationException,

            SAXException, IOException, TransformerFactoryConfigurationError,

            TransformerConfigurationException, TransformerException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse("./WebRoot/xml/t6.xml");

        // 创建结点

        Element e = doc.createElement("language");

        // 为新创建的节点添加内容

        e.setTextContent("Chinese");

        // 为新创建的节点添加属性

        e.setAttribute("aa", "xxx");

        // 为新创建的节点获取父节点，并append新创建的结点

        doc.getElementsByTagName("books").item(1).appendChild(e);

        // 使用Transformer将内存中更新过的xml文档写入实际的xml文档中

        TransformerFactory tfactory = TransformerFactory.newInstance();

        Transformer tf = tfactory.newTransformer();

        tf.transform(new DOMSource(doc), new StreamResult(new File(

                "./WebRoot/xml/t6.xml")));

    }

deleteElement()：删除节点

找到他的父节点

父节点删除要删除的节点

更新文档(把修改后的xml文档同步到本地)

private static void deleteElement() throws ParserConfigurationException,

            SAXException, IOException, TransformerFactoryConfigurationError,

            TransformerConfigurationException, TransformerException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(new File("./WebRoot/xml/t6.xml"));

        // 得到待删除的结点

        Element e = (Element) doc.getElementsByTagName("language").item(0);

        // 获取结点的父节点，然后删除该子结点

        e.getParentNode().removeChild(e);

        // 使用Transformer将内存中更新过的xml文档写入实际的xml文档中

        TransformerFactory tfactory = TransformerFactory.newInstance();

        Transformer tf = tfactory.newTransformer();

        tf.transform(new DOMSource(doc), new StreamResult(new File(

                "./WebRoot/xml/t6.xml")));

    }
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