XML文档读取-DOM

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）

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")));
    }

posted on 2017-11-14 09:35 song.yan 阅读(220) 评论(0) 编辑收藏举报

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XML文档读取-DOM

五个功能函数：

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