JDK提供的XML解析方式分为两种：DOM方式和SAX方式
DOM：Document Object Model。需要读取整个XML文档，先需要在内存中构架代表整个DOM树的Document对象，可以进行随机访问. 需要考虑内存.适合增删改
SAX：Simple API for XML。采用事件驱动的方式解析XML文件，边读边对文档进行处理.适合读取
其他的xml解析包:Dom4J, PullParser(安卓)
Dom4J实现类似SAX方式, API类似DOM方式
DOM @JDK
public class DomTest {
// 解析xml获取document对象
private Document getDocument() throws ParserConfigurationException,
SAXException, IOException {
// 1. 获得工厂
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
// 2. 获得 builder对象
DocumentBuilder builder = factory.newDocumentBuilder();
// 3. 解析xml得带document对象
Document document = builder.parse("src/book.xml");
return document;
}
// 将内存中的document对象写回xml文件中
private void writeBack2Xml(Document document)
throws TransformerFactoryConfigurationError,
TransformerConfigurationException, TransformerException {
TransformerFactory factory = TransformerFactory.newInstance();
Transformer transformer = factory.newTransformer();
transformer.transform(new DOMSource(document), new StreamResult("src/book.xml"));
}
// 读取节点文本
@Test
public void testReadContent() throws Exception{
Document document = getDocument();
//根据标签名获得节点列表
NodeList nodeList = document.getElementsByTagName("书");
System.out.println("长度 : " + nodeList.getLength());
// 返回第一个节点
Node firstNode = nodeList.item(0);
// 返回文本内容
String result = firstNode.getTextContent();
System.out.println(result);
}
// 读取节点的属性值
@Test
public void testReadAttribute() throws Exception{
Document document = getDocument();
NodeList nodeList = document.getElementsByTagName("书");
// 确认本Node为元素节点后加强转
Node node = nodeList.item(0);
if (node instanceof Element) {
Element firstElement = (Element) node;
String result = firstElement.getAttribute("出版社");
System.out.println(result);
}
}
// 添加节点
@Test
public void testAddPrice() throws Exception, SAXException, IOException{
Document document = getDocument();
Node firstNode = document.getElementsByTagName("书").item(0);
Element newElement = document.createElement("售价");
newElement.setTextContent("79.00元");
firstNode.appendChild(newElement);
writeBack2Xml(document); //写回
}
// 删除节点
@Test
public void testDelete() throws Exception, SAXException, IOException{
Document document = getDocument();
NodeList priceNodeList = document.getElementsByTagName("售价");
for (int i = 0; i < priceNodeList.getLength(); i++) {
Node node = priceNodeList.item(i);
if("39.00元".equals(node.getTextContent())){
// 从父节点删除子节点, 类似dom的api
node.getParentNode().removeChild(node);
}
}
writeBack2Xml(document);
}
// 打印所有元素节点的名称
@Test
public void testPrintAllElementsName() throws Exception, SAXException, IOException{
Document document = getDocument();
// 递归打印
printAllElementsName(document);
}
public void printAllElementsName(Node node){
// 打印本节点
if(Node.ELEMENT_NODE==node.getNodeType()){
System.out.println(node.getNodeName());
}
// 处理子节点
NodeList childNodes = node.getChildNodes();
for (int i = 0; i < childNodes.getLength(); i++) { //递归出口: 循环完成
Node item = childNodes.item(i);
printAllElementsName(item);
}
}
}
SAX @JDK
public class SaxTest {
public static void main(String[] args) throws Exception, SAXException {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
XMLReader reader = parser.getXMLReader();
reader.setContentHandler(new MyDefaultHandler());
reader.parse("src/book.xml");
}
}
class MyDefaultHandler extends DefaultHandler {
// 作为被调用方, 流程不是这边控制, 所以定义状态位或计数器来标记流程进行的位置
private boolean isPrice = false;
private int count =1;
@Override
public void startElement(String uri, String localName, String qName, // qName标签名
Attributes attributes) throws SAXException {
if ("售价".equals(qName)) {
isPrice = true;
count++;
}
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
if ("售价".equals(qName)) {
isPrice = false;
}
}
// 读到文本了
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if (isPrice&&count==3) {
System.out.println("文本: " + new String(ch, start, length));
}
}
}
Dom4J
public class Dom4JTest {
private Document getDocument() throws DocumentException {
// 获得 代表 xml 文件的 document 对象
SAXReader reader = new SAXReader();
Document document = reader.read("src/book.xml");
return document;
}
private void wirteBack2Xml(Document document) throws UnsupportedEncodingException, FileNotFoundException, IOException {
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("UTF-8");
XMLWriter writer = new XMLWriter(new FileOutputStream("src/book.xml"), format);
writer.write(document);
writer.close();
}
// 读取节点的文本内容
// 由于 dom4j采用sax方式去解析的xml文档, 所以dom4j不能直接获得深层次的某个节点, 需要一级级获得
@Test
public void testReadContent() throws Exception{
Document document = getDocument();
Element rootElement = document.getRootElement();
Element firstLevelElement = rootElement.element("ele1");
Element secondLevelElement = firstLevelElement.element("ele2");
String value = secondLevelElement.getText();
System.out.println(value);
}
// 读取属性值
@Test
public void testReadAttribute() throws Exception{
Document document = getDocument();
Element rootElement = document.getRootElement();
List<Element> list = rootElement.elements("书");
Element secondElement = list.get(1);
Attribute attribute = secondElement.attribute("出版社");
String value = attribute.getValue();
System.out.println(value);
}
// 添加节点
@Test
public void testAddPrice() throws Exception{
Document document = getDocument();
Element rootElement = document.getRootElement();
Element secondBookElement = (Element) rootElement.elements("书").get(1);
// 创建新节点
secondBookElement.addElement("newEle").setText("this is new Element");
wirteBack2Xml(document);
}
// 删除节点
@Test
public void testDeletePrice() throws Exception{
Document document = getDocument();
Element rootElement = document.getRootElement();
Element secondBookElement = (Element) rootElement.elements("书").get(1);
Element targetBookPrice = (Element) secondBookElement.elements("售价").get(0);
// 拿到父节点, 然后删除这个子节点
targetBookPrice.getParent().remove(targetBookPrice);
wirteBack2Xml(document);
}
}