Java读写XML
1. DOM方式解析
直接将整个xml文档加载到内存中，并转化为DOM树，消耗资源较大，不适合大文档的扫描。
- 读取标签的值
package demo;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
public class DomParseXml {
public static void main(String[] args) {
// @formatter:off
/* 包括：元素节点，属性节点和文本节点。
Bloodroot
Sanguinaria canadensis
4
Mostly Shady
$2.44
031599
Columbine
Aquilegia canadensis <---把这个值取出来
3
Mostly Shady
$9.37
030699
/*
// @formatter:on
/**
* 层次： 元素 文本
* doc -> nodeList -> item -> Element -> item -> getFirstChild -> getNodeValue
*/
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("src/altova.xml");
NodeList nodeList = doc.getElementsByTagName("PLANT"); // 不一定非要从根元素开始
Element e = (Element) nodeList.item(1);
System.out.println(e.getElementsByTagName("BOTANICAL").item(0).getFirstChild().getNodeValue());
} catch (Exception e) {
e.printStackTrace();
}
}
}
- 读取标签的属性
xml文件如下：
<beauties>
<girl>
<name id="01" nickname="琴操">花如月name>
<age>26age>
<feature>长腿皮裤feature>
girl>
<girl>
<name id="02" nickname="凤起">镜流水name>
<age>24age>
<feature>碎花长裙feature>
girl>
<girl>
<name id="03" nickname="悲鸣">柳叶飘name>
<age>22age>
<feature>瑜伽裤feature>
girl>
beauties>
package demo;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class Dom02 {
private void printAttr(Node node) {
NamedNodeMap nnm = node.getAttributes();
for (int i = 0; i < nnm.getLength(); i++) {
Node attrNode = (Node) nnm.item(i);
System.out.println("\t" + attrNode.getNodeName() + "：" + attrNode.getFirstChild().getNodeValue());
}
}
public void printXml() {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse("src/beauties.xml");
NodeList nodeList = doc.getElementsByTagName("girl");
for (int i = 0; i < nodeList.getLength(); i++) {
Element e = (Element) nodeList.item(i);
System.out.print(e.getElementsByTagName("name").item(0).getNodeName() + "：");
System.out.println(e.getElementsByTagName("name").item(0).getFirstChild().getNodeValue());
printAttr(e.getElementsByTagName("name").item(0));
System.out.print(e.getElementsByTagName("age").item(0).getNodeName() + "：");
System.out.println(e.getElementsByTagName("age").item(0).getFirstChild().getNodeValue());
System.out.print(e.getElementsByTagName("feature").item(0).getNodeName() + "：");
System.out.println(e.getElementsByTagName("feature").item(0).getFirstChild().getNodeValue());
System.out.println("------------------");
}
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
Dom02 dom02 = new Dom02();
dom02.printXml();
}
}
2. SAX方式解析
事件驱动的流式方式（逐行扫描），资源占用少。适合大文档的扫描，但只能读无法写。
package demo;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class Sax01 extends DefaultHandler {
@Override
public void startDocument() throws SAXException {
System.out.println("开始扫描文档");
}
@Override
public void endDocument() throws SAXException {
System.out.println("文档扫描结束");
}
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
System.out.println("开始扫描元素：" + qName);
System.out.println("解析属性：");
for (int i = 0; i < attributes.getLength(); i++) {
System.out.println("\t" + attributes.getQName(i) + "=" + attributes.getValue(i));
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
System.out.println("扫描元素结束：" + qName);
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
System.out.println("扫描文本节点：" + new String(ch, start, length));
}
public static void main(String[] args) throws Exception {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser parser = factory.newSAXParser();
parser.parse("src/beauties.xml", new Sax01());
}
}
输出
开始扫描文档
开始扫描元素：beauties
解析属性：
扫描文本节点：
开始扫描元素：girl
解析属性：
扫描文本节点：
开始扫描元素：name
解析属性：
id=01
nickname=琴操
扫描文本节点：花如月
扫描元素结束：name
扫描文本节点：
开始扫描元素：age
解析属性：
扫描文本节点：26
扫描元素结束：age
扫描文本节点：
开始扫描元素：feature
解析属性：
扫描文本节点：长腿皮裤
扫描元素结束：feature
扫描文本节点：
扫描元素结束：girl
扫描文本节点：
开始扫描元素：girl
解析属性：
扫描文本节点：
开始扫描元素：name
解析属性：
id=02
nickname=凤起
扫描文本节点：镜流水
扫描元素结束：name
扫描文本节点：
开始扫描元素：age
解析属性：
扫描文本节点：24
扫描元素结束：age
扫描文本节点：
开始扫描元素：feature
解析属性：
扫描文本节点：碎花长裙
扫描元素结束：feature
扫描文本节点：
扫描元素结束：girl
扫描文本节点：
开始扫描元素：girl
解析属性：
扫描文本节点：
开始扫描元素：name
解析属性：
id=03
nickname=悲鸣
扫描文本节点：柳叶飘
扫描元素结束：name
扫描文本节点：
开始扫描元素：age
解析属性：
扫描文本节点：22
扫描元素结束：age
扫描文本节点：
开始扫描元素：feature
解析属性：
扫描文本节点：瑜伽裤
扫描元素结束：feature
扫描文本节点：
扫描元素结束：girl
扫描文本节点：
扫描元素结束：beauties
文档扫描结束
3. JDOM解析
- 官网：http://www.jdom.org/
- 可以读写XML文档。
package demo;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.XMLOutputter;
public class Jdom01 {
public static void main(String[] args) {
Element beauties = new Element("beauties");
Element girl = new Element("girl");
beauties.addContent(girl);
Element name = new Element("name");
Attribute id = new Attribute("id", "01");
Attribute nickname = new Attribute("nickname", "琴操");
name.setAttribute(id);
name.setAttribute(nickname);
name.setText("花如月");
girl.addContent(name);
Element age = new Element("age");
age.setText("26");
girl.addContent(age);
Element feature = new Element("feature");
feature.setText("碎花长裙");
girl.addContent(feature);
Document document = new Document(beauties);
XMLOutputter out = new XMLOutputter();
out.setFormat(out.getFormat().setEncoding("UTF-8"));
try {
out.output(document, new FileOutputStream("src/dream.xml"));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
- 输出（缺点不能格式化）
<beauties>
<girl>
<name id="01" nickname="琴操">花如月name>
<age>26age>
<feature>碎花长裙feature>
girl>
beauties>
- 遍历xml
package demo;
import java.util.List;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;
public class Jdom02 {
public static void main(String[] args) throws Exception {
SAXBuilder builder = new SAXBuilder();
Document document = builder.build("src/beauties.xml");
Element beauties = document.getRootElement();
List<Element> girls = beauties.getChildren("girl");
for (Element girl : girls) {
String girlName = girl.getChildText("name");
Element name = girl.getChild("name");
String id = name.getAttributeValue("id");
String nickname = name.getAttributeValue("nickname");
String age = girl.getChildText("age");
String feature = girl.getChildText("feature");
System.out.println(girlName + "( id=" + id + ", nickname=" + nickname + " ) , " + age + ", " + feature);
}
}
}
4. DOM4J解析
- 创建xml
package demo;
import java.io.FileOutputStream;
import org.dom4j.Document;
import org.dom4j.DocumentHelper;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;
public class Dom4j01 {
public static void main(String[] args) {
Document document = DocumentHelper.createDocument();
Element beauties = document.addElement("beauties");
Element girl = beauties.addElement("girl");
Element name = girl.addElement("name");
name.setText("镜花月");
name.addAttribute("id", "01");
name.addAttribute("nickname", "琴操");
Element age = girl.addElement("age");
age.setText("28");
Element feature = girl.addElement("feature");
feature.setText("飞天花袍");
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("UTF-8");
XMLWriter writer;
try {
writer = new XMLWriter(new FileOutputStream("src/newgirl.xml"), format);
writer.write(document);
writer.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
- 遍历xml
package demo;
import java.util.Iterator;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class Dom4j02 {
public static void main(String[] args) throws Exception {
SAXReader saxReader = new SAXReader();
Document document = saxReader.read("src/beauties.xml");
Element beauties = document.getRootElement();
Iterator<Element> it = beauties.elementIterator();
while (it.hasNext()) {
Element e = it.next(); // girl
Element name = e.element("name");
String girlName = name.getText();
String id = name.attributeValue("id");
String nickname = name.attributeValue("nickname");
Element age = e.element("age");
String ageValue = age.getText();
Element feature = e.element("feature");
String featureValue = feature.getText();
System.out.println(
girlName + "( id=" + id + ", nickname=" + nickname + " ) , " + ageValue + ", " + featureValue);
}
}
}