xml文件有几种定义形式？解析方式?

1.定义形式

两种定义形式，dtd文档类型定义和schema模式。具体区别自行百度吧，我觉得大概知道怎么用就可以了。

2.解析方式

解析文件book.xml ，以下给出代码示例。

<?xml version="1.0" encoding="UTF-8"?>
<books>
    <book bookno="001">
        <title>java</title>
        <author>李白</author>
        <price>80</price>
    </book>
    <book bookno="002">
        <title>python</title>
        <author>杜甫</author>
        <price>100</price>
    </book>
</books>

book实体，解析代码中通用的。

package xml.domparser;

/**
 * @Auther: laughing
 * @Date: 2019-3-5 16:28
 * @Description: Book实体
 */
public class Book {

    private String bookNo;
    private String title;
    private String author;
    private Double price;

    public Book() {

    }

    public Book(String bookNo, String title, String author, Double price) {
        this.bookNo = bookNo;
        this.title = title;
        this.author = author;
        this.price = price;
    }

    public String getBookNo() {
        return bookNo;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public Double getPrice() {
        return price;
    }

    public void setBookNo(String bookNo) {
        this.bookNo = bookNo;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Book{" +
                "bookNo='" + bookNo + '\'' +
                ", title='" + title + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                '}';
    }
}

2.1 dom 解析

package xml.domparser;

import org.w3c.dom.*;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * @Auther: laughing
 * @Date: 2019-3-5 16:27
 * @Description: DOM解析XML文件
 */
public class DOMXMLParser {

    public List<Book> parseXml(String fileName) {

        List<Book> list = new ArrayList<>();

        //文档生成器工厂对象
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        Document document = null;
        try {
            /*文档生成器*/
            DocumentBuilder builder = factory.newDocumentBuilder();
            document = builder.parse(new File(fileName));
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        //根节点
        Node rootNode = (Node) document.getDocumentElement();
        /*获取<book>元素列表*/
        NodeList bookElementList = rootNode.getChildNodes();

        for (int i = 0; i < bookElementList.getLength(); i++) {
            /*获取单个<book>元素*/
            Node bookelement = (Node) bookElementList.item(i);
            /*取节点名称*/
            if (bookelement.getNodeName().equals("book")) {
                Book book = new Book();
                /*节点属性*/
                NamedNodeMap map = bookelement.getAttributes();
                Node booknoNode = (Node) map.getNamedItem("bookno");
                String bookNoString = booknoNode.getNodeValue();
                book.setBookNo(bookNoString.trim());

                /*获取子节点*/
                NodeList subBookElementList = bookelement.getChildNodes();
                for (int j = 0; j < subBookElementList.getLength(); j++) {

                    /*子节点*/
                    Node subElemtNode = (Node) subBookElementList.item(j);

                    /*子节点元素名称*/
                    String subElementNameString = subElemtNode.getNodeName();

                    /*分析子节点元素名称从而获取内容*/
                    if (subElementNameString.equals("title")) {
                        /*获取节点内容*/
                        book.setTitle(subElemtNode.getTextContent().trim());
                    }
                    if (subElementNameString.equals("author")) {
                        /*获取节点内容*/
                        book.setAuthor(subElemtNode.getTextContent().trim());
                    }
                    if (subElementNameString.equals("price")) {
                        /*获取节点内容*/
                        book.setPrice(Double.parseDouble(subElemtNode.getTextContent().trim()));
                    }

                }
                list.add(book);
            }
        }
        return list;
    }

    public static void main(String[] args) {
        DOMXMLParser parser = new DOMXMLParser();
        List<Book> list = parser.parseXml("book.xml");
        System.out.println("DOM解析结果: ");
        for (Book book : list) {
            System.out.println(book);
        }
    }
}

2.2 SAX解析

package xml.saxparser;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import java.util.ArrayList;
import java.util.List;

/**
 * @Auther: laughing
 * @Date: 2019-3-5 17:19
 * @Description: sax解析器
 */
public class XMLHandler extends DefaultHandler {

    private List<Book> list;
    private Book book;
    private String tag;

    public XMLHandler() {
        super();
    }

    // 返回解析到的集合。
    public List<Book> getList() {
        return list;
    }

    /**
     * 文档解析开始，初始化集合
     *
     * @throws SAXException
     */
    @Override
    public void startDocument() throws SAXException {
        System.out.println("文档解析开始--");
        list = new ArrayList<Book>();
    }

    /**
     * 文档解析结束
     *
     * @throws SAXException
     */
    @Override
    public void endDocument() throws SAXException {
        System.out.println("文档解析结束--");
    }

    // 开始标记
    // qName;表示标签名
    // attributes:属性集合

    /**
     * 开始标记
     *
     * @param uri
     * @param localName
     * @param qName      标签名字
     * @param attributes 属性集合
     * @throws SAXException
     * 主要来处理标签上的属性
     */
    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        tag = qName;
        if ("book".equals(tag)) {
            this.book = new Book();
            for (int i = 0; i < attributes.getLength(); i++) {
                String q = attributes.getQName(i);
                String v = attributes.getValue(i);
                if ("bookno".equals(q)) {
                    book.setBookNo(v);
                }
            }
        }
    }

    /**
     * 结束标记 把处理的对象放到list中
     *
     * @param uri
     * @param localName
     * @param qName
     * @throws SAXException
     */
    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if ("book".equals(qName)) {
            list.add(book);
        }
        tag = "";
    }

    // 标记与标记之间的内容
    @Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        String str = new String(ch, start, length);
        // 判断标记
        if ("title".equals(tag)) {
            book.setTitle(str);
        } else if ("author".equals(tag)) {
            book.setAuthor(str);
        } else if ("price".equals(tag)) {
            book.setPrice(Double.valueOf(str));
        }
    }

    public static void main(String[] args) throws Exception {
        //得到解析工厂。
        SAXParserFactory factory = SAXParserFactory.newInstance();
        //通过工厂得到解析器。
        SAXParser parser = factory.newSAXParser();
        XMLHandler handler = new XMLHandler();
        //将文件和Handler，和解析器相关联。
        parser.parse("book.xml", handler);
        //需要得到解析后的集合。
        List<Book> list = handler.getList();
        for (Book s : list) {
            System.out.println(s);
        }
    }
}

2.3 JDOM解析

需要的依赖

 <dependency>
            <groupId>jdom</groupId>
            <artifactId>jdom</artifactId>
            <version>1.0</version>
        </dependency>

package xml.jdomparser;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;

import java.io.IOException;
import java.util.List;

/**
 * @Auther: laughing
 * @Date: 2019-3-5 17:52
 * @Description: jdom 解析
 */
public class JdomParser {

    public static void main(String[] args) throws Exception {
        parser();
    }

    private static void parser() throws JDOMException, IOException {

        SAXBuilder saxBuilder = new SAXBuilder();
        Document doc = saxBuilder.build("book.xml");
        // 获取根元素
        Element rootElement = doc.getRootElement();
        // 取名字为book的所有元素
        List list = rootElement.getChildren("book");
        for (int i = 0; i < list.size(); i++) {
            Element element = (Element) list.get(i);
            // 获取元素中属性为name的值
            String bookno = element.getAttributeValue("bookno");
            // 取disk子元素capacity的内容  
            String title = element.getChildText("title");
            String author = element.getChildText("author");
            String price = element.getChildText("price");

            System.out.println(bookno + "-" + title + "-" + author + "-" + price);
        }
    }
}

2.4 DOM4J解析

package xml.dom4j;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

import java.io.File;
import java.io.FileOutputStream;
import java.util.List;

/**
 * @Auther: laughing
 * @Date: 2019-3-5 18:19
 * @Description: dom4j解析xml 创建 xml
 */
public class Dom4jparser {

    public static void main(String[] args) throws Exception {
        // parser();
        write();
    }

    private static void parser() throws DocumentException {
        SAXReader saxReader = new SAXReader();
        Document document = saxReader.read("book.xml");

        //根节点
        Element rootElement = document.getRootElement();
        //孩子们
        List<Element> elements = rootElement.elements("book");

        for (Element child : elements) {

            String bookNo = child.attributeValue("bookno");
            String title = child.elementText("title");
            String author = child.elementText("author");
            String price = child.elementText("price");

            System.out.println(bookNo + "-" + title + "-" + author + "-" + price);
        }
    }

    private static void write() throws Exception {

        Document doc = DocumentHelper.createDocument();
        Element books = doc.addElement("books");

        Element book1 = books.addElement("book");
        Element title1 = book1.addElement("title");
        Element author1 = book1.addElement("author");
        Element price1 = book1.addElement("price");

        book1.addAttribute("bookno", "001");
        title1.setText("java");
        author1.setText("李白");
        price1.setText("10");

        Element book2 = books.addElement("book");
        Element title2 = book2.addElement("title");
        Element author2 = book2.addElement("author");
        Element price2 = book2.addElement("price");

        book2.addAttribute("bookno", "002");
        title2.setText("java2");
        author2.setText("李白2");
        price2.setText("102");

        //格式化输出
        OutputFormat format = OutputFormat.createPrettyPrint();
        format.setEncoding("utf-8");
        File file = new File("book1.xml");
        //写文件
        XMLWriter xmlWriter = new XMLWriter(new FileOutputStream(file), format);
        xmlWriter.write(doc);
    }
}

xml文件有几种定义形式？解析方式?

1.定义形式

2.解析方式

2.1 dom 解析

2.2 SAX解析

2.3 JDOM解析

2.4 DOM4J解析

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