java 解析dom 树方式来解析XML文件

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原理：

将XML 文件解析成dom 树(即Document 对象)，对document 对象进行操作得到各个节点的名称和节点的值。

需要的 jar 包：

xml-apis-1.4.01.jar

几个需要澄清的概念，如下图1,2,3，在代码中都有相应指定：

图 1

图 2

图 3

代码：

Book.xml 文件

<?xml version="1.0" encoding="UTF-8"?>  <books>      <book id="12">          <name>thinking in java</name>          <price>85.5</price>      </book>      <book id="15">          <name>Spring in Action</name>          <price>39.0</price>      </book>  </books>

DomParseService 类

package domParse;import java.io.IOException;import java.io.InputStream;import java.util.ArrayList;import java.util.List;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.ParserConfigurationException;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 DomParseService {public static List<Book> getBooks(InputStream inputSream) throws ParserConfigurationException, SAXException, IOException {List<Book> list = new ArrayList<Book>();DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();Document document = builder.parse(inputSream);Element element = document.getDocumentElement();NodeList bookNodelist = element.getElementsByTagName("book");//所有的book 节点 for(int i=0;i<bookNodelist.getLength();i++) {Book book = new Book();Element bookElement = (Element)bookNodelist.item(i);//这个item() 函数返回的类型DeferredElementImpl，是Element 接口的实现类，Element 实现了Node，<span style="color:#ff0000;">如图1</span>，这个函数本身返回的是Node 接口类型book.setId(Integer.parseInt(bookElement.getAttribute("id")));NodeList bookChildNodelist = bookElement.getChildNodes();for(int j = 0;j < bookChildNodelist.getLength();j++) {if(bookChildNodelist.item(j).getNodeType() == Node.ELEMENT_NODE) { //看看这里面有什么属性node（有TEXT_NODE ，即那些空白，<span style="color:#ff0000;">如图2</span>）  if("name".equals(bookChildNodelist.item(j).getNodeName())) {book.setName(bookChildNodelist.item(j).getFirstChild().getNodeValue());} else if("price".equals(bookChildNodelist.item(j).getNodeName())) {book.setPrice(Float.parseFloat(bookChildNodelist.item(j).getFirstChild().getNodeValue()));  //<span style="color:#ff0000;">如图3</span>}}}list.add(book);}return list;}}

Book 类

package domParse;public class Book {private int id;private String name;private float price;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public float getPrice() {return price;}public void setPrice(float price) {this.price = price;}}

Main 类

package domParse;import java.io.IOException;import java.util.List;import javax.xml.parsers.ParserConfigurationException;import org.xml.sax.SAXException;public class Main {public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException {List<Book> bookList = DomParseService.getBooks(new Main().getClass().getClassLoader().getResourceAsStream("Book.xml"));//.getResourceAsStream("Book.xml")for(Book book : bookList) {System.out.println("this book id, name, price : " + String.valueOf(book.getId()) + book.getName() + book.getPrice());}}}

运行结果：

this book id, name, price : 12 thinking in java 85.5
this book id, name, price : 15 Spring in Action 39.0

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