Java 解析 XML

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由W3C提供的接口，它将整个XML文档读入内存，构建一个DOM树来对各个节点(Node)进行操作。
示例代码：

<?xml version="1.0" encoding="UTF-8"?><university name="pku"> <college name="c1"> <class name="class1"> <student name="stu1" sex='male' age="21" /> <student name="stu2" sex='female' age="20" /> <student name="stu3" sex='female' age="20" /> </class> <class name="class2"> <student name="stu4" sex='male' age="19" /> <student name="stu5" sex='female' age="20" /> <student name="stu6" sex='female' age="21" /> </class> </college> <college name="c2"> <class name="class3"> <student name="stu7" sex='male' age="20" /> </class> </college> <college name="c3"> </college></university>后文代码中有使用到text.xml（该文档放在src路径下，既编译后在classes路径下），都是指该xml文档。

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package test.xml;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
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;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;
import org.xml.sax.SAXException;
/**
* dom读写xml
* @author whwang
*/
public class TestDom {
public static void main(String[] args) {
read();
//write();
}
publicstaticvoid read() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
// root <university>
Element root = doc.getDocumentElement();
if (root ==null)return;
System.err.println(root.getAttribute("name"));
// all college node
NodeList collegeNodes = root.getChildNodes();
if (collegeNodes ==null)return;
for(int i =0; i < collegeNodes.getLength(); i++) {
Node college = collegeNodes.item(i);
if (college !=null && college.getNodeType() == Node.ELEMENT_NODE) {
System.err.println("\t" + college.getAttributes().getNamedItem("name").getNodeValue());
// all class node
NodeList classNodes = college.getChildNodes();
if (classNodes ==null)continue;
for (int j = 0; j < classNodes.getLength(); j++) {
Node clazz = classNodes.item(j);
if (clazz != null && clazz.getNodeType() == Node.ELEMENT_NODE) {
System.err.println("\t\t" + clazz.getAttributes().getNamedItem("name").getNodeValue());
// all student node
NodeList studentNodes = clazz.getChildNodes();
if (studentNodes == null) continue;
for (int k = 0; k < studentNodes.getLength(); k++) {
Node student = studentNodes.item(k);
if (student != null && student.getNodeType() == Node.ELEMENT_NODE) {
System.err.print("\t\t\t" + student.getAttributes().getNamedItem("name").getNodeValue());
System.err.print(" " + student.getAttributes().getNamedItem("sex").getNodeValue());
System.err.println(" " + student.getAttributes().getNamedItem("age").getNodeValue());
}
}
}
}
}
}
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void write() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream in = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(in);
// root <university>
Element root = doc.getDocumentElement();
if (root ==null)return;
// 修改属性
root.setAttribute("name","tsu");
NodeList collegeNodes = root.getChildNodes();
if (collegeNodes !=null) {
for (int i = 0; i <collegeNodes.getLength() -1; i++) {
// 删除节点
Node college = collegeNodes.item(i);
if (college.getNodeType() == Node.ELEMENT_NODE) {
String collegeName = college.getAttributes().getNamedItem("name").getNodeValue();
if ("c1".equals(collegeName) ||"c2".equals(collegeName)) {
root.removeChild(college);
} else if ("c3".equals(collegeName)) {
Element newChild = doc.createElement("class");
newChild.setAttribute("name","c4");
college.appendChild(newChild);
}
}
}
}
// 新增节点
Element addCollege = doc.createElement("college");
addCollege.setAttribute("name","c5");
root.appendChild(addCollege);
Text text = doc.createTextNode("text");
addCollege.appendChild(text);
// 将修改后的文档保存到文件
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transFormer = transFactory.newTransformer();
DOMSource domSource = new DOMSource(doc);
File file = new File("src/dom-modify.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
FileOutputStream out = new FileOutputStream(file);
StreamResult xmlResult =new StreamResult(out);
transFormer.transform(domSource, xmlResult);
System.out.println(file.getAbsolutePath());
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (TransformerConfigurationException e) {
e.printStackTrace();
} catch (TransformerException e) {
e.printStackTrace();
}
}
}
该代码只要稍做修改，即可变得更加简洁，无需一直写if来判断是否有子节点。