XML处理
- DOM
DOM解析要求解析器将整个XML文件全部加载到内存中，生成一个Document对象。
优点：元素和元素之间保留结构，关系，可以针对元素进行增删改查操作。
缺点：如果XML文件过大，可能会导致内存溢出。 - SAX
SAX解析是一种更加高效的解析方式。它是逐行扫描，边扫描边解析，并且以时间驱动的方式进行具体的解析，每解析一行都会触发一个事件。
优点：不会出现内存溢出的问题，可以处理大文件。
缺点：只能读，不能写。 - 常见的解析XML类库
解析器就是根据不同的解析方式提供具体的实现，为了方便开发人员来解析XML，有一些方便操作的类库。具体如下所示：
1.dom4j:比较简单的XML解析类库；
2.Jsoup：功能强大的DOM方式解析的类库，尤其对HTML的解析更加方便，所以可以使用Jsoup来爬取网页的数据。
JDK内置DOM
XML文件
books.xml
<?xml version="1.0" encoding="UTF-8"?>
<books><!-- book至少出现一次 --><book><!-- id --><id>1</id><!-- 书名 --><name>《JAVA从入门到放弃》</name><!-- 作者属性type：可选（man|woman）默认值 “man”属性age：必填属性--><author type="man" age="23">张三</author></book><book><id>2</id><name>《这是一本书》</name><author type="woman" age="32">李四</author></book>
</books>
JDK内置DOM读XML
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;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;/*** JDK内置DOM读XML** @author Anna.* @date 2024/3/31 17:42*/
public class JavaDomReadDemo {public static void main(String[] args) throws Exception {new JavaDomReadDemo().read();}public void read() throws ParserConfigurationException, IOException, SAXException {// 获取资源路径String path = this.getClass().getResource("books.xml").getPath();// 获取文件判断文件是否存在File file = new File(path);if (!file.exists() || !file.isFile()) {throw new RuntimeException("获取资源失败");}// 从DocumentBuilderFactory获得DocumentBuilder。 DocumentBuilder包含用于从 XML 文档中获取 DOM 文档实例的 API。DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();// parse()方法将 XML 文件解析为DocumentDocument doc = documentBuilder.parse(file);System.out.printf("根节点: %s", doc.getDocumentElement().getNodeName());// 循环打印NodeList nList = doc.getElementsByTagName("book");for (int i = 0; i < nList.getLength(); i++) {Node nNode = nList.item(i);System.out.println("");System.out.printf("元素: %s", nNode.getNodeName());if (nNode.getNodeType() == Node.ELEMENT_NODE) {Element elem = (Element) nNode;String id = elem.getElementsByTagName("id").item(0).getTextContent();String name = elem.getElementsByTagName("name").item(0).getTextContent();Element authorNode = (Element) elem.getElementsByTagName("author").item(0);String author = elem.getElementsByTagName("author").item(0).getTextContent();String type = authorNode.getAttribute("type");String age = authorNode.getAttribute("age");System.out.println("");System.out.printf("id: %s - name:%s - author:%s[type=%s,age=%s]", id, name, author, type, age);}}}}
执行结果
使用NodeIterator读取文本
import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.DocumentTraversal;
import org.w3c.dom.traversal.NodeFilter;
import org.w3c.dom.traversal.NodeIterator;
import org.xml.sax.SAXException;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;/*** JDK内置DOM读XML* 使用NodeIterator读取文本** @author Anna.* @date 2024/3/31 17:42*/
public class JavaDomReadDemo2 {public static void main(String[] args) throws Exception {new JavaDomReadDemo2().read();}public void read() throws ParserConfigurationException, IOException, SAXException {// 获取资源路径String path = this.getClass().getResource("books.xml").getPath();// 获取文件判断文件是否存在File file = new File(path);if (!file.exists() || !file.isFile()) {throw new RuntimeException("获取资源失败");}// 从DocumentBuilderFactory获得DocumentBuilder。 DocumentBuilder包含用于从 XML 文档中获取 DOM 文档实例的 API。DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();// parse()方法将 XML 文件解析为DocumentDocument doc = documentBuilder.parse(file);DocumentTraversal trav = (DocumentTraversal) doc;NodeIterator it = trav.createNodeIterator(doc.getDocumentElement(), NodeFilter.SHOW_ELEMENT, null, true);for (Node node = it.nextNode(); node != null;node = it.nextNode()) {// 判断是否有属性if (node.hasAttributes()) {String attrStr = getAttrStr(node.getAttributes());System.out.printf("元素名称：%s-元素值：%s-属性：%s %n", node.getNodeName(), node.getTextContent(), "".equalsIgnoreCase(attrStr) ? "null" : attrStr, node.getNodeType());} else {System.out.printf("元素名称：%s-元素值：%s%n", node.getNodeName(), node.getTextContent());}}}private String getAttrStr(NamedNodeMap attributes) {StringBuffer sb = new StringBuffer();if (attributes != null && attributes.getLength() > 0) {sb.append("[");for (int i = 0; i < attributes.getLength(); i++) {Node item = attributes.item(i);sb.append(item.getNodeName()).append("=").append(item.getNodeValue()).append(" ");}sb.append("]");}return sb.toString();}
}
执行结果
使用NodeIterator读取文本自定义NodeFilter
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.traversal.DocumentTraversal;
import org.w3c.dom.traversal.NodeFilter;
import org.w3c.dom.traversal.NodeIterator;
import org.xml.sax.SAXException;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.File;
import java.io.IOException;/*** JDK内置DOM读XML* 使用NodeIterator读取文本自定义NodeFilter* @author Anna.* @date 2024/3/31 17:42*/
public class JavaDomReadDemo3 {public static void main(String[] args) throws Exception {new JavaDomReadDemo3().read();}public void read() throws ParserConfigurationException, IOException, SAXException {// 获取资源路径String path = this.getClass().getResource("books.xml").getPath();// 获取文件判断文件是否存在File file = new File(path);if (!file.exists() || !file.isFile()) {throw new RuntimeException("获取资源失败");}// 从DocumentBuilderFactory获得DocumentBuilder。 DocumentBuilder包含用于从 XML 文档中获取 DOM 文档实例的 API。DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();// parse()方法将 XML 文件解析为DocumentDocument doc = documentBuilder.parse(file);DocumentTraversal trav = (DocumentTraversal) doc;NodeIterator it = trav.createNodeIterator(doc.getDocumentElement(), NodeFilter.SHOW_ELEMENT, new MyFilter(), true);for (Node node = it.nextNode(); node != null;node = it.nextNode()) {// 判断是否有属性if(node.hasAttributes()){String attrStr = getAttrStr(node.getAttributes());System.out.printf("元素名称：%s-元素值：%s-属性：%s %n", node.getNodeName(),node.getTextContent(),"".equalsIgnoreCase(attrStr) ? "null" : attrStr, node.getNodeType());}else {System.out.printf("元素名称：%s-元素值：%s%n", node.getNodeName(),node.getTextContent());}}}private String getAttrStr(NamedNodeMap attributes){StringBuffer sb = new StringBuffer();if(attributes != null && attributes.getLength() > 0){sb.append("[");for(int i = 0; i < attributes.getLength(); i++){Node item = attributes.item(i);sb.append(item.getNodeName()).append("=").append(item.getNodeValue()).append(" ");}sb.append("]");}return sb.toString();}/*** 自定义过滤器* 实现NodeFilter接口* 通过返回NodeFilter.FILTER_ACCEPT和NodeFilter.FILTER_REJECT来控制要使用的节点* @author Anna.* @date 2024/3/31 18:50*/static class MyFilter implements NodeFilter {@Overridepublic short acceptNode(Node thisNode) {if (thisNode.getNodeType() == Node.ELEMENT_NODE) {Element e = (Element) thisNode;String nodeName = e.getNodeName();if ("author".equals(nodeName)) {return NodeFilter.FILTER_ACCEPT;}}return NodeFilter.FILTER_REJECT;}}
}
执行结果
JDK内置DOM写XML
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.File;
import java.util.HashMap;
import java.util.Map;/*** JDK内置DOM写XML** @author Anna.* @date 2024/3/31 17:42*/
public class JavaDomWriteDemo {public static void main(String[] args) throws Exception {new JavaDomWriteDemo().write();}public void write() throws Exception {DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();Document doc = builder.newDocument();// 创建根节点Element root = doc.createElementNS("", "books");doc.appendChild(root);// 设置子元素Map<String, String> book1 = new HashMap<String, String>();book1.put("type", "man");book1.put("age", "34");root.appendChild(createBook(doc, "1", "《JAVA从入门到放弃》", "张三", book1));Map<String, String> book2 = new HashMap<String, String>();book2.put("type", "man");book2.put("age", "34");root.appendChild(createBook(doc, "2", "《这是一本书》", "李四", book2));// Java DOM 使用Transformer生成 XML 文件。 之所以称为转换器，是因为它也可以使用 XSLT 语言转换文档。TransformerFactory transformerFactory = TransformerFactory.newInstance();Transformer transf = transformerFactory.newTransformer();// 设置文档的编码和缩进transf.setOutputProperty(OutputKeys.ENCODING, "UTF-8");transf.setOutputProperty(OutputKeys.INDENT, "yes");transf.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");// DOMSource保存 DOM 树DOMSource source = new DOMSource(doc);// 获取资源路径String path = System.getProperty("user.dir") + File.separator + "01-xml-04-xml-handle/java-dom-demo/src/main/resources";File myFile = new File(path + File.separator + "books2.xml");StreamResult console = new StreamResult(System.out);StreamResult file = new StreamResult(myFile);// 写入控制台和文件transf.transform(source, console);transf.transform(source, file);}/*** 创建Book* e** @param doc* @param id* @param name* @param author* @return org.w3c.dom.Node* @author Anna.* @date 2024/3/31 19:03*/private static Node createBook(Document doc, String id, String name, String author, Map<String, String> attrsMap) {Element book = doc.createElement("book");book.setAttribute("id", id);book.appendChild(createUserElement(doc, "id", id, null));book.appendChild(createUserElement(doc, "name", name, null));book.appendChild(createUserElement(doc, "author", author, attrsMap));return book;}/*** 创建子节点** @param doc* @param name* @param value* @param attrsMap* @return org.w3c.dom.Node* @author Anna.* @date 2024/3/31 19:02*/private static Node createUserElement(Document doc, String name, String value, Map<String, String> attrsMap) {Element node = doc.createElement(name);node.appendChild(doc.createTextNode(value));if (attrsMap != null && attrsMap.size() > 0) {for (Map.Entry entry : attrsMap.entrySet()) {node.setAttribute(entry.getKey().toString(), entry.getValue().toString());}}return node;}
}
执行结果
DOM4J读写XML
引入MAVEN坐标
<dependency><groupId>org.dom4j</groupId><artifactId>dom4j</artifactId><version>2.1.3</version>
</dependency>
SAX读XML
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;import java.io.File;
import java.util.Iterator;/*** SAX读XML文件** @author Anna.* @date 2024/3/31 19:40*/
public class SaxReadDemo {public static void main(String[] args) {new SaxReadDemo().read();}public void read() {// 获取资源路径String path = this.getClass().getResource("books.xml").getPath();// 获取文件判断文件是否存在File file = new File(path);if (!file.exists() || !file.isFile()) {throw new RuntimeException("获取资源失败");}// 1 创建SAXReader对象，用于读取XML文件SAXReader saxReader = new SAXReader();// 读取XML文件，得到document对象try {Document document = saxReader.read(new File(path));// 获取根元素Element rootElement = document.getRootElement();System.out.println("根元素名称：" + rootElement.getName());// 获取根元素下所有子元素Iterator<?> iterator = rootElement.elementIterator();while (iterator.hasNext()) {// 取出元素Element element = (Element) iterator.next();System.out.println("子元素名称：" + element.getName());// 获取子元素Element id = element.element("id");Element name = element.element("name");Element author = element.element("author");System.out.printf("子元素的子元素值-id：%s -name: %s --author:%s[type=%s,age=%s]%n",id.getStringValue(), name.getText(),author.getText(),// 获取author属性typeauthor.attribute("type").getValue(),// 获取author属性ageauthor.attribute("age").getValue());}} catch (DocumentException e) {e.printStackTrace();}}
}执行结果
DOM4J写XML
Dom4j的常用API说明
| 方法 | 操作 |
|---|---|
| Element getRootElement(); | 获取XML文件的根节点 |
| String getName(); | 返回标签的名称 |
| List < Element > elements(); | 获取标签所有的子标签 |
| String arrtributeVallue(String name) ; | 获取指定属性名称的属性值 |
| String getText(); | 获取标签的文本 |
| String elementText(String name); | 获取指定名称的子标签的文本，返回子标签文本的值 |
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;import java.io.File;
import java.io.FileWriter;
import java.io.IOException;/*** Dom4j写XML文件** @author Anna.* @date 2024/3/31 19:40*/
public class Dom4jWriteDemo {public static void main(String[] args) {String path = System.getProperty("user.dir") + File.separator + "01-xml-04-xml-handle/dom4j-demo/src/main/resources";new Dom4jWriteDemo().write(path + File.separator + "books2.xml");}public void write(String path) {// 通过documentHelper生成一个Documen对象Document document = DocumentHelper.createDocument();// 添加并得到根元素Element books = document.addElement("books");// 为根元素添加子元素Element book = books.addElement("book");// 为book添加子元素Element id = book.addElement("id");Element name = book.addElement("name");Element author = book.addElement("author");// 为子元素添加文本id.addText("1");name.addText("《Java自学基础》");author.addText("张三");author.addAttribute("type", "man");author.addAttribute("age", "12");// 将DOC输出到XML文件 简单输出
// Writer writer = null;
// try {
// writer = new FileWriter(new File(path));
// document.write(writer);
// // 关闭资源
// writer.close();
// } catch (IOException e) {
// e.printStackTrace();
// } finally {
// if (writer != null) {
// try {
// writer.close();
// } catch (IOException e) {
// e.printStackTrace();
// }
// }
// }// 美化格式输出OutputFormat format = OutputFormat.createPrettyPrint();XMLWriter xmlWriter = null;try {xmlWriter = new XMLWriter(new FileWriter(new File(path)), format);xmlWriter.write(document);// 关闭资源xmlWriter.close();} catch (IOException e) {e.printStackTrace();} finally {if (xmlWriter != null) {try {xmlWriter.close();} catch (IOException e) {e.printStackTrace();}}}}
}
执行结果
