一、XML简单介绍
xml是可扩展标记语言，主要用来标记数据、定义数据类型，很适合万维网传输。
xml特点：
- xml是一种标记语言。非常类似HTML
- xml的设计宗旨是数据传输，而不是显示数据
- xml标签没有被提前定义，须要自行定义标签
- xml被设计为具有自我描写叙述性
- xml是W3C的推荐标准
xml和html对照：
- XML被设计为传输和存储数据，其焦点是数据的内容。
- html被设计用来显示数据，其焦点是数据的外观。
- html旨在显示信息，而xml旨在传输信息。
演示样例：
<bookstore>
<book category="CHILDREN">
<title>harry Potter</title>
<author>JK.Rowing</author>
<year>2005</year>
<price>35.2</price>
</book>
</bookstore>元素能够包括其它元素、文本或者两者的混合物。元素也能够拥有属性。<bookstore>和<book>都拥有元素内容，<author>仅仅有文本内容，<book>还拥有属性。
二、Dom方式读取xml
新建一个java project。在工程根文件夹下放置一个languages.xml：
<?Dom方式读取xml文件：xml version="1.0" encoding="UTF-8"?> <Languages cat="it"> <lan id="1"> <name>java</name> <ide>Eclipse</ide> </lan> <lan id="2"> <name>Swift</name> <ide>Xcode</ide> </lan> <lan id="3"> <name>C#</name> <ide>Visual Studio</ide> </lan> </Languages>
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
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 ReadXml {
public static void main(String[] args) {
try {
// Dom方式
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(new File("language.xml"));
Element root = document.getDocumentElement();
System.out.println("cat=" + root.getAttribute("cat"));
NodeList list = root.getElementsByTagName("lan");
for (int i = 0; i < list.getLength(); i++) {
Element lan = (Element) list.item(i);
System.out.println("------------------");
System.out.println("id=" + lan.getAttribute("id"));
/*
* Element name=(Element)
* lan.getElementsByTagName("name").item(0);
* System.out.println("name="+name.getTextContent()); Element
* ide=(Element) lan.getElementsByTagName("ide").item(0);
* System.out.println("ide="+ide.getTextContent());
*/
NodeList clist = lan.getChildNodes();
for (int j = 0; j < clist.getLength(); j++) {
Node c = clist.item(j);
if (c instanceof Element) {
System.out.println(c.getNodeName() + "=" + c.getTextContent());
}
}
}
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
输出：
cat=it ------------------ id=1 name=java ide=Eclipse ------------------ id=2 name=Swift ide=Xcode ------------------ id=3 name=C# ide=Visual Studio
package ucas.yp.xml;
import java.io.File;
import java.io.StringWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
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 CreateXml {
public static void main(String[] args) {
try {
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document=builder.newDocument();
Element root=document.createElement("Languages");
root.setAttribute("cat", "it");
Element lan1=document.createElement("lan");
lan1.setAttribute("id", "1");
Element name1=document.createElement("name");
name1.setTextContent("Java");
Element ide1=document.createElement("ide");
ide1.setTextContent("Eclipse");
lan1.appendChild(name1);
lan1.appendChild(ide1);
//从内到外一层层包装
Element lan2=document.createElement("lan");
lan2.setAttribute("id", "2");
Element name2=document.createElement("name");
name2.setTextContent("Swift");
Element ide2=document.createElement("ide");
ide2.setTextContent("Xcode");
lan2.appendChild(name2);
lan2.appendChild(ide2);
Element lan3=document.createElement("lan");
lan3.setAttribute("id", "3");
Element name3=document.createElement("name");
name3.setTextContent("C#");
Element ide3=document.createElement("ide");
ide3.setTextContent("Visual Studio");
lan3.appendChild(name3);
lan3.appendChild(ide3);
root.appendChild(lan1);
root.appendChild(lan2);
root.appendChild(lan3);
document.appendChild(root);
TransformerFactory trFactory=TransformerFactory.newInstance();
Transformer transformer=trFactory.newTransformer();
StringWriter writer=new StringWriter();
transformer.transform(new DOMSource(document), new StreamResult(writer));
//----- 字符串输出
System.out.println(writer.toString());
//-----生成xml文件
transformer.transform(new DOMSource(document), new StreamResult( new File("newxml.xml")));
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (TransformerConfigurationException e) {
e.printStackTrace();
} catch (TransformerException e) {
e.printStackTrace();
}
}
}
Dom4j是一个优秀的java操作xml的库，具有性能优异、功能强大和极其易使用的特点。下载地址：http://www.dom4j.org/dom4j-1.6.1/
package ucas.yp.xml;
import java.io.FileWriter;
import java.io.IOException;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;
import org.dom4j.io.XMLWriter;
public class TestDom4j {
public static void main(String[] args) {
String xmlString = "<bookstore><book><title>harry Potter</title><author>JK.Rowing</author><year>2005</year><price>35.2</price></book></bookstore>";
try {
Document document = DocumentHelper.parseText(xmlString);
// 打印
System.out.println(document.asXML());
//生成xml文件
XMLWriter writer = new XMLWriter(new FileWriter("book.xml"));
writer.write(document);
writer.close();
} catch (DocumentException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
刷新project文件夹。能够看到新生成的book.xml。