xml文件：
为了更好地描述数据，我们采用xml的内容+数据的描述形式，这便于更直观地读懂数据及其表达的内容
xml解析方法：
DOM方法：
比较麻烦的一个方法，需要不停地用for遍历子树，然后输出结果：
例如看user.xml
它地读取就是逐层地（或者逐行地根据名称）解析，逐层的异常繁琐，可以看看源码：
package xml.dom;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class DomReader
{
public static void main(String[] a)
{
recursiveTraverse(); //自上而下进行访问
System.out.println("========华丽丽的分割线==========");
traverseBySearch(); //根据名称进行搜索
}
public static void recursiveTraverse()
{
try
{
//采用Dom解析xml文件
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse("users.xml");
//获取所有的一级子节点
NodeList usersList = document.getChildNodes();
System.out.println(usersList.getLength()); //1
for (int i = 0; i < usersList.getLength(); i++)
{
Node users = usersList.item(i); //1 users
NodeList userList = users.getChildNodes(); //获取二级子节点user的列表
System.out.println("==" + userList.getLength()); //9
for (int j = 0; j < userList.getLength(); j++) //9
{
Node user = userList.item(j);
if (user.getNodeType() == Node.ELEMENT_NODE)
{
NodeList metaList = user.getChildNodes();
System.out.println("====" + metaList.getLength()); //7
for (int k = 0; k < metaList.getLength(); k++) //7
{
//到最后一级文本
Node meta = metaList.item(k);
if (meta.getNodeType() == Node.ELEMENT_NODE)
{
System.out.println(metaList.item(k).getNodeName()
+ ":" + metaList.item(k).getTextContent());
}
}
System.out.println();
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
public static void traverseBySearch()
{
try
{
//采用Dom解析xml文件
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse("users.xml");
Element rootElement = document.getDocumentElement();
NodeList nodeList = rootElement.getElementsByTagName("name");
if(nodeList != null)
{
for (int i = 0 ; i < nodeList.getLength(); i++)
{
Element element = (Element)nodeList.item(i);
System.out.println(element.getNodeName() + " = " + element.getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}再看看DOM写入，逻辑主要是先构建对象，然后描述对象之间的关系：
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
public class DomWriter {
public static void main(String[] args) {
try {
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dbBuilder = dbFactory.newDocumentBuilder();
//新创建一个Document节点
Document document = dbBuilder.newDocument();
if (document != null)
{
Element docx = document.createElement("document"); //都是采用Document创建元素
Element element = document.createElement("element");
element.setAttribute("type", "paragraph");
element.setAttribute("alignment", "left"); //element增加2个属性
Element object = document.createElement("object");
object.setAttribute("type", "text");
Element text = document.createElement("text");
text.appendChild(document.createTextNode("ggggg")); //给text节点赋值
Element bold = document.createElement("bold");
bold.appendChild(document.createTextNode("true")); //给bold节点赋值
object.appendChild(text); //把text节点挂在object下
object.appendChild(bold); //把bold节点挂在object下
element.appendChild(object); //把object节点挂在element下
docx.appendChild(element); //把element节点挂在docx下
document.appendChild(docx); //把docx挂在document下
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource source = new DOMSource(document);
//定义目标文件
File file = new File("dom_result.xml");
StreamResult result = new StreamResult(file);
//将xml内容写入到文件中
transformer.transform(source, result);
System.out.println("write xml file successfully");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}结果：
sax解析：
push方法，每行都看，然后实现接口的五个方法，进行处理逻辑的编写
先看看xml：
需求是书的title都弄出来
代码如下：
package xml.sax;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
public class SAXReader {
public static void main(String[] args) throws SAXException, IOException {
XMLReader parser = XMLReaderFactory.createXMLReader();
BookHandler bookHandler = new BookHandler();
parser.setContentHandler(bookHandler);
parser.parse("books.xml");
System.out.println(bookHandler.getNameList());
}
}
class BookHandler extends DefaultHandler {
private List<String> nameList;
private boolean title = false;
public List<String> getNameList() {
return nameList;
}
// xml文档加载时
public void startDocument() throws SAXException {
System.out.println("Start parsing document...");
nameList = new ArrayList<String>();
}
// 文档解析结束
public void endDocument() throws SAXException {
System.out.println("End");
}
// 访问某一个元素
public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException {
if (qName.equals("title")) {
title = true;
}
}
// 结束访问元素
public void endElement(String namespaceURI, String localName, String qName) throws SAXException {
// End of processing current element
if (title) {
title = false;
}
}
// 访问元素正文
public void characters(char[] ch, int start, int length) {
if (title) {
String bookTitle = new String(ch, start, length);
System.out.println("Book title: " + bookTitle);
nameList.add(bookTitle);
}
}
}主要的实现逻辑就是通过一个bool变量标记当前行是不是title的，然后提起title的内容即可，缺点就是每行都要走一遍
stax解析：
基于pull模型的，可以有效地定位想抓取的内容。分为流模式和事件模式，流模式更好用，事件还是要头中尾的处理：
代码如下：
package xml.stax;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;
public class StaxReader {
public static void main(String[] args) {
StaxReader.readByStream();
System.out.println("========华丽丽的分割线==========");
StaxReader.readByEvent();
}
//流模式
public static void readByStream() {
String xmlFile = "books.xml";
XMLInputFactory factory = XMLInputFactory.newFactory();
XMLStreamReader streamReader = null;
try {
streamReader = factory.createXMLStreamReader(new FileReader(xmlFile));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
// 基于指针遍历
try {
while (streamReader.hasNext()) {
int event = streamReader.next();
// 如果是元素的开始
if (event == XMLStreamConstants.START_ELEMENT) {
// 列出所有书籍名称
if ("title".equalsIgnoreCase(streamReader.getLocalName())) {
System.out.println("title:" + streamReader.getElementText());
}
}
}
streamReader.close();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
// 事件模式
public static void readByEvent() {
String xmlFile = "books.xml";
XMLInputFactory factory = XMLInputFactory.newInstance();
boolean titleFlag = false;
try {
// 创建基于迭代器的事件读取器对象
XMLEventReader eventReader = factory.createXMLEventReader(new FileReader(xmlFile));
// 遍历Event迭代器
while (eventReader.hasNext()) {
XMLEvent event = eventReader.nextEvent();
// 如果事件对象是元素的开始
if (event.isStartElement()) {
// 转换成开始元素事件对象
StartElement start = event.asStartElement();
// 打印元素标签的本地名称
String name = start.getName().getLocalPart();
//System.out.print(start.getName().getLocalPart());
if(name.equals("title"))
{
titleFlag = true;
System.out.print("title:");
}
// 取得所有属性
Iterator attrs = start.getAttributes();
while (attrs.hasNext()) {
// 打印所有属性信息
Attribute attr = (Attribute) attrs.next();
//System.out.print(":" + attr.getName().getLocalPart() + "=" + attr.getValue());
}
//System.out.println();
}
//如果是正文
if(event.isCharacters())
{
String s = event.asCharacters().getData();
if(null != s && s.trim().length()>0 && titleFlag)
{
System.out.println(s.trim());
}
}
//如果事件对象是元素的结束
if(event.isEndElement())
{
EndElement end = event.asEndElement();
String name = end.getName().getLocalPart();
if(name.equals("title"))
{
titleFlag = false;
}
}
}
eventReader.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}总结：
大体了解一下即可，要用的时候再参考代码
自此我们确实可以对xml进行读取和写入
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
