DOM模型(documentobject model)
•DOM解析器在解析XML文档时，会把文档中的所有元素，按照其出现的层次关系，解析成一个个Node对象(节点)。
•在dom中，节点之间关系如下：
•位于一个节点之上的节点是该节点的父节点(parent)
•一个节点之下的节点是该节点的子节点（children）
•同一层次，具有相同父节点的节点是兄弟节点（sibling）
•一个节点的下一个层次的节点集合是节点后代(descendant)
父、祖父节点
首先引出要解析的xml文件：
<?xml version="1.0" encoding="UTF-8"?><书架> <书> <书名>javaweb开发</书名> <作者 id="12">张孝祥</作者> <售价>59元</售价> </书> <书> <书名>JavaScript网页开发</书名> <作者>张孝祥</作者> <售价>28.00元</售价> </书> </书架>
以下即是对xml的增删改查操作：
import java.io.FileOutputStream;
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.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.junit.Before;
import org.junit.Test;
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 Demo3 {
/**
* 利用dom完成文档的crud
* @param args
* @throws Exception
* @throws ParserConfigurationException
* @throws Exception
* @throws SAXException
* @throws Exception
*/
private Document document;
@Before
public void before() throws Exception{
//获得dom解析工厂类
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
//得到dom解析器
DocumentBuilder builder = factory.newDocumentBuilder();
//解析xml文件
document = builder.parse("src/book.xml");
}
//遍历
@Test
public void listXml() throws ParserConfigurationException,SAXException,Exception{
list(document);
}
public void list(Node node){
//打印结点的名称
System.out.println(node.getNodeName());
//获得所有子节点
NodeList list = node.getChildNodes();
for(int i=0;i<list.getLength();i++){
Node child = list.item(i);
//递归整个dom树
list(child);
}
}
//读取书名节点的值：<书名>javaweb开发</书名>
@Test
public void test1(){
Document document = this.document;
Node node = document.getElementsByTagName("书名").item(0);
String value = node.getTextContent();
System.out.println(value);
}
//读取书名属性的值：<售价 type="rmb">39.00元</售价>
@Test
public void test2(){
Document document = this.document;
Node node = document.getElementsByTagName("售价").item(0);
Element price = (Element) node; //发现node满足不了，把node强转成相应类型
String attValue = price.getAttribute("type");
System.out.println(attValue);
}
//向xml文档中添加售价节点
@Test
public void test3() throws Exception{
Document document = this.document;
//创建要挂的节点
Element price = document.createElement("售价");
price.setTextContent("59元");
//把创建的结点挂到书节点下
Node book = document.getElementsByTagName("书").item(0);
book.appendChild(price);
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
//向xml文档中指定位置上添加售价节点
@Test
public void test4() throws Exception{
Document document = this.document;
//创建要添加的节点
Element price = document.createElement("售价");
price.setTextContent("59元");
//得到要向哪个节点上挂子节点
Node book = document.getElementsByTagName("书").item(0);
//向参考节点前，挂新节点
book.insertBefore(price,document.getElementsByTagName("售价").item(0));
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
//向xml文档添加节点属性
@Test
public void test5() throws Exception{
Document document = this.document;
//得到要添加属性的节点
Element author = (Element) document.getElementsByTagName("作者").item(0);
author.setAttribute("id","12"); //向节点挂属性
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
//删除xml文档中的售价节点
@Test
public void test6() throws Exception{
Document document = this.document;
//得到要删除的节点
Node price = document.getElementsByTagName("售价").item(0);
//得到要删除的节点的父亲
Node parent = document.getElementsByTagName("书").item(0);
parent.removeChild(price);
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
//删除2 : 删除售价节点所在的书结点
@Test
public void test7() throws Exception{
Document document = this.document;
//得到要删除的节点
Node price = document.getElementsByTagName("售价").item(0);
price.getParentNode().getParentNode().removeChild(price.getParentNode());
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
@Test
public void test8() throws Exception{
Document document = this.document;
document.getElementsByTagName("售价").item(1).setTextContent("19元");
//把内存中更新后对象树，重新定回到xml文档中
TransformerFactory factory = TransformerFactory.newInstance();
Transformer tf = factory.newTransformer();
tf.transform(new DOMSource(document),new StreamResult(new FileOutputStream("src/book.xml")));
}
}
