DOM 一些知识的介绍

• 首先得到：得到 DOM 解析器的工厂实例
• DocumentBuilderFactory domfac=DocumentBuilderFactory.newInstance();
• 然后从DOM工厂获得DOM解析器
• DocumentBuilder dombuilder=domfac.newDocumentBuilder();
• 把要解析的XML文档转化为输入流，以便DOM解析器解析它
• InputStream is= new FileInputStream(“test1.xml”);
• 解析XML文档的输入流，得到一个Document
• Document doc=dombuilder.parse(is);
• 得到 XML 文档的根节点
• Element root=doc.getDocumentElement();
• 得到节点的子节点
• NodeList books=root.getChildNodes();

下面是两个实际例子第一个dom解析xml例子

package com.sec.xml;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.util.Iterator;
import java.util.Vector;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
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;
public class TestXML {
/** Vector类 Vector非常类似ArrayList，但是Vector是同步的。由Vector创建的Iterator，
* 虽然和ArrayList创建的 Iterator是同一接口，但是，因为Vector是同步的，
* 当一个Iterator被创建而且正在被使用，另一个线程改变了Vector的状态
*（例如，添加或删除了一些元素）
* 这时调用Iterator的方法时将抛出ConcurrentModificationException
*因此必须捕获该异常。
*/
Vector students_Vector;
private Vector readXMLFile(String file) throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
Document doc = builder.parse(file); // 获取到xml文件
// 下面开始读取
Element root = doc.getDocumentElement(); // 获取根元素
NodeList students = root.getElementsByTagName("学生");
students_Vector = new Vector();
for (int i = 0; i < students.getLength(); i++) {
// 一次取得每一个学生元素
Element ss = (Element) students.item(i);
// 创建一个学生的实例
student stu = new student();
stu.setSex(ss.getAttribute("性别"));
NodeList names = ss.getElementsByTagName("姓名");
Element e = (Element) names.item(0);
Node t = e.getFirstChild();
stu.setName(t.getNodeValue());
NodeList ages = ss.getElementsByTagName("年龄");
e = (Element) ages.item(0);
t = e.getFirstChild();
stu.setAge(Integer.parseInt(t.getNodeValue()));
students_Vector.add(stu);
}
return students_Vector;
}
/**
* 功能：直接提取XML格式字符串中的信息
*/
private Vector readXMLString(String xmlStr) throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream inputStream = new ByteArrayInputStream(xmlStr.getBytes());
Document doc = builder.parse(inputStream); //
// 下面开始读取
Element root = doc.getDocumentElement(); // 获取根元素
NodeList students = root.getElementsByTagName("学生");
students_Vector = new Vector();
for (int i = 0; i < students.getLength(); i++) {
// 一次取得每一个学生元素
Element ss = (Element) students.item(i);
// 创建一个学生的实例
student stu = new student();
stu.setSex(ss.getAttribute("性别"));
NodeList names = ss.getElementsByTagName("姓名");
Element e = (Element) names.item(0);
Node t = e.getFirstChild();
stu.setName(t.getNodeValue());
NodeList ages = ss.getElementsByTagName("年龄");
e = (Element) ages.item(0);
t = e.getFirstChild();
stu.setAge(Integer.parseInt(t.getNodeValue()));
students_Vector.add(stu);
}
return students_Vector;
}
// 将Document内容 写入XML字符串并返回
private String callWriteXmlString(Document doc, String encoding) {
try {
Source source = new DOMSource(doc);
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
OutputStreamWriter write = new OutputStreamWriter(outStream);
Result result = new StreamResult(write);
Transformer xformer = TransformerFactory.newInstance()
.newTransformer();
xformer.setOutputProperty(OutputKeys.ENCODING, encoding);
xformer.transform(source, result);
return outStream.toString();
} catch (TransformerConfigurationException e) {
e.printStackTrace();
return null;
} catch (TransformerException e) {
e.printStackTrace();
return null;
}
}
/**
* 功能：生成XML格式的字符串
*/
public String writeXMLString() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
try {
builder = dbf.newDocumentBuilder();
} catch (Exception e) {
}
Document doc = builder.newDocument();
Element root = doc.createElement("路过java学习网1");
doc.appendChild(root); // 将根元素添加到文档上
// 获取学生信息
for (int i = 0; i < students_Vector.size(); i++) {
student s = (student) students_Vector.get(i);
// 创建一个学生
Element stu = doc.createElement("学生");
stu.setAttribute("性别", s.getSex());
root.appendChild(stu);// 添加属性
// 创建文本姓名节点
Element name = doc.createElement("姓名");
stu.appendChild(name);
Text tname = doc.createTextNode(s.getName());
name.appendChild(tname);
// 创建文本年龄节点
Element age = doc.createElement("年龄");
stu.appendChild(age); // 将age添加到学生节点上
Text tage = doc.createTextNode(String.valueOf(s.getAge()));
age.appendChild(tage); // 将文本节点放在age节点上
}
try {
String result = callWriteXmlString(doc, "gb2312");
return result;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
/**
* 主函数
*/
public static void main(String args[]) {
String str = "F:\\student.xml";// 读取本地
// String str = "\\student.xml";//相对路径读取
TestXML t = new TestXML();
System.out.println("解析原始XML文件：");
try {
Vector v = t.readXMLFile(str);
Iterator it = v.iterator();
while (it.hasNext()) {
student s = (student) it.next();
System.out.println(s.getName() + "\t" + s.getAge() + "\t"
+ s.getSex());
}
} catch (Exception e) {
e.printStackTrace();
}
String xmlStr = t.writeXMLString();//注意这个生成只是打印在控制台是伪xml
System.out.println("\n生成的XML字符串：\n" + xmlStr);
try {
Vector v = t.readXMLString(xmlStr);
Iterator it = v.iterator();
System.out.println("\n解析生成的XML字符串：");
while (it.hasNext()) {
student s = (student) it.next();
System.out.println(s.getName() + "\t" + s.getAge() + "\t"
+ s.getSex());
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
class student {
private String sex;
private String name;
private int age;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void setSex(String s) {
sex = s;
}
public String getSex() {
return sex;
}
public void setName(String n) {
name = n;
}
public String getName() {
return name;
}
}

//对应xml student.xml

<?xml version="1.0" encoding="gb2312"?>
<路过学习网>
<学生 性别 = "女">
<姓名>路过</姓名>
<年龄>15</年龄>
</学生>
<学生 性别 = "男">
<姓名>java</姓名>
<年龄>16</年龄>
</学生>
</路过学习网>

第二个dom解析xml例子

package com.sec.xml;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
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 TestXML2 {
public static void main(String[] args) {
TestXML2 reader = new TestXML2();
}
public TestXML2(){
DocumentBuilderFactory domfac = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder domBuilder = domfac.newDocumentBuilder();
InputStream is = new FileInputStream(new File("F:/test.xml"));
Document doc = domBuilder.parse(is);
Element root = doc.getDocumentElement();
NodeList books = root.getChildNodes();
if(books!=null){
for (int i = 0; i < books.getLength(); i++) {
Node book = books.item(i);
if(book.getNodeType()==Node.ELEMENT_NODE) {
//取得节点的属性值
String email=book.getAttributes().getNamedItem("email")
.getNodeValue();
System.out.println(email);
//注意，节点的属性也是它的子节点。它的节点类型也是Node.ELEMENT_NODE
//轮循子节点
for(Node node=book.getFirstChild();node!=null;
node=node.getNextSibling()) {
if(node.getNodeType()==Node.ELEMENT_NODE) {
if(node.getNodeName().equals("name")) {
// String name=node.getNodeValue();
String name1=node.getFirstChild().getNodeValue();
// System.out.println(name);
System.out.println(name1);
}
if(node.getNodeName().equals("price")) {
String price=node.getFirstChild().getNodeValue();
System.out.println(price);
}
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

//对应xml student.xml

<?xml version="1.0" encoding="utf-8" ?>
- <books>
- <book email="zhoujunhui">
<name>rjzjh</name>
<price>jjjjjj</price>
</book>
- <book email="sdsdd">
<name>rjzjh1</name>
<price>jjjjjj1</price>
</book>
</books>