XML优点:平台无关性,语言无关性,系统无关性
XML在不同的语言里解析方式都是一样的,只不过实现的语法不同而已。基本的解析方式有两种,一种叫SAX,另一种叫DOM。SAX是基于事件流的解析,DOM是基于XML文档树结构的解析.假设我们XML的内容和结构如下:
下面是解析XMl常用的Dom和Sex方法:
- <?xml version="1.0" encoding="UTF-8"?>
- <employees>
- <employee>
- <name>Darren</name>
- <sex>man</sex>
- <age>25</age>
- </employee>
- </employees>
- package com.darren.test.xml;
- public interface XmlParse {
- void createXml(String path);
- void parseXml(String path);
- }
1、DOM生成和解析XML文档
为 XML 文档的已解析版本定义了一组接口。解析器读入整个文档,然后构建一个驻留内存的树结构,然后代码就可以使用 DOM 接口来操作这个树结构。
优点:整个文档树在内存中,便于操作;支持删除、修改、重新排列等多种功能;
缺点:将整个文档调入内存(包括无用的节点),浪费时间和空间;使用场合:一旦解析了文档还需多次访问这些数据;硬件资源充足(内存、cpu)。
- package com.darren.test.xml;
- import java.io.FileOutputStream;
- import java.io.PrintWriter;
- import javax.xml.parsers.DocumentBuilder;
- import javax.xml.parsers.DocumentBuilderFactory;
- import javax.xml.transform.OutputKeys;
- import javax.xml.transform.Transformer;
- 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;
- import org.w3c.dom.Node;
- import org.w3c.dom.NodeList;
- public class DomParse implements XmlParse {
- private static DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
- @Override
- public void createXml(String path) {
- try {
- DocumentBuilder builder = factory.newDocumentBuilder();
- Document document = builder.newDocument();
- // 创建根节点
- Element root = document.createElement("employees");
- // 添加根节点
- document.appendChild(root);
- // 创建一级子节点
- Element employee = document.createElement("employee");
- // 操作一
- // 创建二级子节点
- Element name = document.createElement("name");
- // 为二级子节点添加值
- name.appendChild(document.createTextNode("Darren"));
- // 把二级子节点放到一级子节点下
- employee.appendChild(name);
- // 同操作一
- Element sex = document.createElement("sex");
- sex.appendChild(document.createTextNode("man"));
- employee.appendChild(sex);
- // 同操作一
- Element age = document.createElement("age");
- age.appendChild(document.createTextNode("25"));
- employee.appendChild(age);
- // 把一级子节点添加到根节点下
- root.appendChild(employee);
- TransformerFactory transformerFactory = TransformerFactory.newInstance();
- Transformer transformer = transformerFactory.newTransformer();
- DOMSource source = new DOMSource(document);
- transformer.setOutputProperty(OutputKeys.ENCODING,"UTF-8");
- transformer.setOutputProperty(OutputKeys.INDENT,"yes");
- PrintWriter pw = new PrintWriter(new FileOutputStream(path));
- StreamResult result = new StreamResult(pw);
- transformer.transform(source,result);
- System.out.println("生成XML文件成功!");
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- @Override
- public void parseXml(String path) {
- try {
- DocumentBuilder builder = factory.newDocumentBuilder();
- Document document = builder.parse(path);
- Element root = document.getDocumentElement();
- NodeList employee = root.getChildNodes();
- outPut(employee);
- System.out.println("解析XML文件成功!");
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- private void outPut(NodeList nodeList) {
- int length = nodeList.getLength();
- for (int i = 0; i < length; i++) {
- Node node = nodeList.item(i);
- // 叶子节点
- if (node.getChildNodes().getLength() == 1) {
- String nodeName = node.getNodeName();
- String nodeValue = node.getTextContent();
- System.out.println(nodeName + ":" + nodeValue);
- }
- // 非叶子节点
- if (node.getChildNodes().getLength() > 1) {
- NodeList subList = node.getChildNodes();
- outPut(subList);
- }
- }
- }
- }
打印结果:
2、SAX生成和解析XML文档
为解决DOM的问题,出现了SAX。SAX ,事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时,发送事件,程序员编写响应这些事件的代码,保存数据。
优点:不用事先调入整个文档,占用资源少;SAX解析器代码比DOM解析器代码小,适于Applet,下载。
缺点:不是持久的;事件过后,若没保存数据,那么数据就丢了;无状态性;从事件中只能得到文本,但不知该文本属于哪个元素;使用场合:Applet;只需XML文档的少量内容,很少回头访问;机器内存少;
- package com.darren.test.xml;
- import org.xml.sax.Attributes;
- import org.xml.sax.SAXException;
- import org.xml.sax.helpers.DefaultHandler;
- public class MySAXHandler extends DefaultHandler {
- // 一般将正式解析前的一些初始化工作放到这里面
- public void startDocument() throws SAXException {
- System.out.println("文档开始打印了");
- }
- // 收尾工作放在endDocument中
- public void endDocument() throws SAXException {
- System.out.println("文档打印结束了");
- }
- // XML解析器遇到XML里面的tag时就会调用这个函数。经常在这个函数内是通过qName俩进行判断而操作一些数据
- public void startElement(String uri,String localName,String qName,Attributes attributes) throws SAXException {
- if (qName.equals("employees")) {
- return;
- }
- if (qName.equals("employee")) {
- return;
- }
- System.out.print(qName + ":");
- }
- // 这个方法与startElement()相对应,解析完一个tag节点后,执行这个方法
- public void endElement(String uri,String qName) throws SAXException {
- }
- // 回调方法。解析器执行完startElement()后,解析完节点的内容后就会执行这个方法,并且参数ch[]就是节点的内容
- public void characters(char[] ch,int start,int length) throws SAXException {
- String value = new String(ch,start,length);
- if (value.startsWith("\n")) {
- return;
- }
- System.out.println(value);
- }
- }
- package com.darren.test.xml;
- import java.io.FileInputStream;
- import java.io.FileOutputStream;
- import java.io.InputStream;
- import javax.xml.parsers.SAXParser;
- import javax.xml.parsers.SAXParserFactory;
- import javax.xml.transform.OutputKeys;
- import javax.xml.transform.Result;
- import javax.xml.transform.Transformer;
- import javax.xml.transform.sax.SAXTransformerFactory;
- import javax.xml.transform.sax.TransformerHandler;
- import javax.xml.transform.stream.StreamResult;
- import org.xml.sax.helpers.AttributesImpl;
- public class SaxParse implements XmlParse {
- @Override
- public void createXml(String path) {
- try {
- SAXTransformerFactory sff = (SAXTransformerFactory) SAXTransformerFactory.newInstance();
- TransformerHandler th = sff.newTransformerHandler();
- Result resultXml = new StreamResult(new FileOutputStream(path));
- th.setResult(resultXml);
- Transformer transformer = th.getTransformer();
- transformer.setOutputProperty(OutputKeys.ENCODING,"UTF-8"); // 编码格式是UTF-8
- transformer.setOutputProperty(OutputKeys.INDENT,"yes"); // 换行
- th.startDocument(); // 开始xml文档
- AttributesImpl attr = new AttributesImpl();
- th.startElement("","","employees",attr); // 定义employees节点
- th.startElement("","employee",attr); // 定义employee节点
- th.startElement("","name",attr); // 定义name节点
- th.characters("Darren".tocharArray(),"Darren".length());
- th.endElement("","name"); // 结束name节点
- th.startElement("","sex",attr); // 定义sex节点
- th.characters("man".tocharArray(),"man".length());
- th.endElement("","sex"); // 结束gender节点
- th.startElement("","age",attr); // 定义age节点
- th.characters("25".tocharArray(),"25".length());
- th.endElement("","age"); // 结束age节点
- th.endElement("","employee"); // 结束employee节点
- th.endElement("","employees"); // 结束employees节点
- th.endDocument(); // 结束xml文档
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- @Override
- public void parseXml(String path) {
- SAXParserFactory saxfac = SAXParserFactory.newInstance();
- try {
- SAXParser saxparser = saxfac.newSAXParser();
- InputStream is = new FileInputStream(path);
- saxparser.parse(is,new MySAXHandler());
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
打印结果:
- 文档开始打印了
- name:Darren
- sex:man
- age:25
- 文档打印结束了
3、DOM4J生成和解析XML文档
DOM4J 是一个非常非常优秀的Java XML API,具有性能优异、功能强大和极端易用使用的特点,同时它也是一个开放源代码的软件。如今你可以看到越来越多的 Java 软件都在使用 DOM4J 来读写 XML,特别值得一提的是连 Sun 的 JAXM 也在用 DOM4J
需要引入dom4j包
打印结果:
- package com.darren.test.xml;
- import java.io.File;
- import java.io.FileWriter;
- import java.io.Writer;
- import java.util.Iterator;
- import org.dom4j.Document;
- import org.dom4j.DocumentHelper;
- import org.dom4j.Element;
- import org.dom4j.io.SAXReader;
- import org.dom4j.io.XMLWriter;
- public class Dom4jParse implements XmlParse {
- @Override
- public void createXml(String path) {
- try {
- Document document = DocumentHelper.createDocument();
- Element employees = document.addElement("employees");
- Element employee = employees.addElement("employee");
- Element name = employee.addElement("name");
- name.setText("Darren");
- Element sex = employee.addElement("sex");
- sex.setText("man");
- Element age = employee.addElement("age");
- age.setText("25");
- Writer fileWriter = new FileWriter(path);
- XMLWriter xmlWriter = new XMLWriter(fileWriter);
- xmlWriter.write(document);
- xmlWriter.close();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- @Override
- @SuppressWarnings("unchecked")
- public void parseXml(String path) {
- try {
- File inputXml = new File(path);
- SAXReader saxReader = new SAXReader();
- Document document = saxReader.read(inputXml);
- Element employees = document.getRootElement();
- Iterator<Element> employeeElements = employees.elementIterator();
- while (employeeElements.hasNext()) {
- Element employee = (Element) employeeElements.next();
- Iterator<Element> nodeElements = employee.elementIterator();
- while (nodeElements.hasNext()) {
- Element node = (Element) nodeElements.next();
- System.out.println(node.getName() + ":" + node.getText());
- }
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- name:Darren
- sex:man
- age:25
4、JDOM生成和解析XML
为减少DOM、SAX的编码量,出现了JDOM;优点:20-80原则,极大减少了代码量。使用场合:要实现的功能简单,如解析、创建等,但在底层,JDOM还是使用SAX(最常用)、DOM、Xanan文档
需要引入jdom包
打印结果:
- package com.darren.test.xml;
- import java.io.FileOutputStream;
- import java.util.List;
- import org.jdom.Document;
- import org.jdom.Element;
- import org.jdom.input.SAXBuilder;
- import org.jdom.output.XMLOutputter;
- public class JDomParse implements XmlParse {
- @Override
- public void createXml(String path) {
- try {
- Element root = new Element("employees");
- Document document = new Document(root);
- Element employee = new Element("employee");
- root.addContent(employee);
- Element name = new Element("name");
- name.setText("Darren");
- employee.addContent(name);
- Element sex = new Element("sex");
- sex.setText("man");
- employee.addContent(sex);
- Element age = new Element("age");
- age.setText("25");
- employee.addContent(age);
- XMLOutputter XMLOut = new XMLOutputter();
- XMLOut.output(document,new FileOutputStream(path));
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- @Override
- @SuppressWarnings("unchecked")
- public void parseXml(String path) {
- try {
- SAXBuilder builder = new SAXBuilder(false);
- Document document = builder.build(path);
- Element root = document.getRootElement();
- List<Element> employeeList = root.getChildren("employee");
- for (Element employee : employeeList) {
- List<Element> employeeInfo = employee.getChildren();
- for (Element info : employeeInfo) {
- System.out.println(info.getName() + ":" + info.getValue());
- }
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
测试类:
- name:Darren
- sex:man
- age:25
- package com.darren.test.xml;
- public class XmlParseTest {
- public static void main(String[] args) {
- // DomParse domParse = new DomParse();
- // domParse.createXml("F:\\employee.xml");
- // domParse.parseXml("F:\\employee.xml");
- // SaxParse saxParse = new SaxParse();
- // saxParse.createXml("F:\\employee.xml");
- // saxParse.parseXml("F:\\employee.xml");
- // Dom4jParse dom4jParse = new Dom4jParse();
- // dom4jParse.createXml("F:\\employee.xml");
- // dom4jParse.parseXml("F:\\employee.xml");
- JDomParse jdomParse = new JDomParse();
- jdomParse.createXml("F:\\employee.xml");
- jdomParse.parseXml("F:\\employee.xml");
- }
- }