JDOM 解析器 可用于读取 XML、解析 xml 以及在更新 XML 文件内容后写入 XML 文件。它将JDOM2 文档 存储在内存中以读取和修改它的值。
将 XML 文档加载到内存后，JDOM2 保持严格的父子类型关系。父类 JDOM 实例（Parent）具有访问其内容的方法，而子类 JDOM 实例（Content）具有访问其父类的方法。
项目结构
请创建此文件夹结构以执行示例。它是一个在eclipse 中创建的简单maven 项目。
请注意，我使用了lambda 表达式 和方法引用，因此您需要配置项目以使用 JDK 1.8。
JDOM2 Maven 依赖
<dependency> <groupId>org.jdom</groupId> <artifactId>jdom2</artifactId> <version>2.0.6</version> </dependency>
要执行 XPath，您还需要 jaxen。
<dependency> <groupId>jaxen</groupId> <artifactId>jaxen</artifactId> <version>1.1.6</version> </dependency>
创建 JDOM2 文档
您可以使用下面列出的任何解析器创建 org.jdom2.Document 实例。它们都解析 XML 并返回内存中的 JDOM 文档。
使用 DOM 解析器
private static Document getDOMParsedDocument(final String fileName) { Document document = null; try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); //If want to make namespace aware. //factory.setNamespaceAware(true); DocumentBuilder documentBuilder = factory.newDocumentBuilder(); org.w3c.dom.Document w3cDocument = documentBuilder.parse(fileName); document = new DOMBuilder().build(w3cDocument); } catch (IOException | SAXException | ParserConfigurationException e) { e.printStackTrace(); } return document; }使用 SAX 解析器
private static Document getSAXParsedDocument(final String fileName) { SAXBuilder builder = new SAXBuilder(); Document document = null; try { document = builder.build(fileName); } catch (JDOMException | IOException e) { e.printStackTrace(); } return document; }使用 StAX 解析器
private static Document getStAXParsedDocument(final String fileName) { Document document = null; try { XMLInputFactory factory = XMLInputFactory.newFactory(); XMLEventReader reader = factory.createXMLEventReader(new FileReader(fileName)); StAXEventBuilder builder = new StAXEventBuilder(); document = builder.build(reader); } catch (JDOMException | IOException | XMLStreamException e) { e.printStackTrace(); } return document; }
读取和过滤 XML 内容
我将阅读 employees.xml 文件。
<employees> <employee id="101"> <firstName>Lokesh</firstName> <lastName>Gupta</lastName> <country>India</country> <department id="25"> <name>ITS</name> </department> </employee> <employee id="102"> <firstName>Brian</firstName> <lastName>Schultz</lastName> <country>USA</country> <department id="26"> <name>DEV</name> </department> </employee> </employees>
读取根节点
使用 document.getRootElement() 方法。
public static void main(String[] args)
{
String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);
Element rootNode = document.getRootElement();
System.out.println("Root Element :: " + rootNode.getName());
}
输出：
Root Element :: employees
读取属性值
使用 Element.getAttributeValue() 方法。
public static void main(String[] args)
{
String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);
Element rootNode = document.getRootElement();
rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
}
private static void readEmployeeNode(Element employeeNode)
{
//Employee Id
System.out.println("Id : " + employeeNode.getAttributeValue("id"));
}
输出：
Id : 101 Id : 102
读取元素值
使用 Element.getChildText() 或 Element.getText() 方法。
public static void main(String[] args)
{
String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);
Element rootNode = document.getRootElement();
rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
}
private static void readEmployeeNode(Element employeeNode)
{
//Employee Id
System.out.println("Id : " + employeeNode.getAttributeValue("id"));
//First Name
System.out.println("FirstName : " + employeeNode.getChildText("firstName"));
//Last Name
System.out.println("LastName : " + employeeNode.getChildText("lastName"));
//Country
System.out.println("country : " + employeeNode.getChild("country").getText());
/**Read Department Content*/
employeeNode.getChildren("department").forEach( ReadXMLDemo::readDepartmentNode );
}
private static void readDepartmentNode(Element deptNode)
{
//Department Id
System.out.println("Department Id : " + deptNode.getAttributeValue("id"));
//Department Name
System.out.println("Department Name : " + deptNode.getChildText("name"));
}
输出：
FirstName : Lokesh LastName : Gupta country : India Department Id : 25 Department Name : ITS FirstName : Brian LastName : Schultz country : USA Department Id : 26 Department Name : DEV
使用 XPath 读取 XML 内容
要使用 xpath 读取任何一组元素的值，您需要编译 XPathExpression 并使用它的 evaluate() 方法。
String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);
XPathFactory xpfac = XPathFactory.instance();
//Read employee ids
XPathExpression<Attribute> xPathA = xpfac.compile("//employees/employee/@id", Filters.attribute());
for (Attribute att : xPathA.evaluate(document))
{
System.out.println("Employee Ids :: " + att.getValue());
}
//Read employee first names
XPathExpression<Element> xPathN = xpfac.compile("//employees/employee/firstName", Filters.element());
for (Element element : xPathN.evaluate(document))
{
System.out.println("Employee First Name :: " + element.getValue());
}
输出：
Employee Ids :: 101 Employee Ids :: 102 Employee First Name :: Lokesh Employee First Name :: Brian
完整的 JDOM2 读取 XML 示例
这是在java中使用JDOM2读取xml的完整代码。
package com.cundage.demo.jdom2;
import java.io.FileReader;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.filter.Filters;
import org.jdom2.input.DOMBuilder;
import org.jdom2.input.SAXBuilder;
import org.jdom2.input.StAXEventBuilder;
import org.jdom2.xpath.XPathExpression;
import org.jdom2.xpath.XPathFactory;
import org.xml.sax.SAXException;
@SuppressWarnings("unused")
public class ReadXMLDemo
{
public static void main(String[] args)
{
String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);
/**Read Document Content*/
Element rootNode = document.getRootElement();
System.out.println("Root Element :: " + rootNode.getName());
System.out.println("\n=================================\n");
/**Read Employee Content*/
rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
System.out.println("\n=================================\n");
readByXPath(document);
}
private static void readEmployeeNode(Element employeeNode)
{
//Employee Id
System.out.println("Id : " + employeeNode.getAttributeValue("id"));
//First Name
System.out.println("FirstName : " + employeeNode.getChildText("firstName"));
//Last Name
System.out.println("LastName : " + employeeNode.getChildText("lastName"));
//Country
System.out.println("country : " + employeeNode.getChild("country").getText());
/**Read Department Content*/
employeeNode.getChildren("department").forEach( ReadXMLDemo::readDepartmentNode );
}
private static void readDepartmentNode(Element deptNode)
{
//Department Id
System.out.println("Department Id : " + deptNode.getAttributeValue("id"));
//Department Name
System.out.println("Department Name : " + deptNode.getChildText("name"));
}
private static void readByXPath(Document document)
{
//Read employee ids
XPathFactory xpfac = XPathFactory.instance();
XPathExpression<Attribute> xPathA = xpfac.compile("//employees/employee/@id", Filters.attribute());
for (Attribute att : xPathA.evaluate(document))
{
System.out.println("Employee Ids :: " + att.getValue());
}
XPathExpression<Element> xPathN = xpfac.compile("//employees/employee/firstName", Filters.element());
for (Element element : xPathN.evaluate(document))
{
System.out.println("Employee First Name :: " + element.getValue());
}
}
private static Document getSAXParsedDocument(final String fileName)
{
SAXBuilder builder = new SAXBuilder();
Document document = null;
try
{
document = builder.build(fileName);
}
catch (JDOMException | IOException e)
{
e.printStackTrace();
}
return document;
}
private static Document getStAXParsedDocument(final String fileName)
{
Document document = null;
try
{
XMLInputFactory factory = XMLInputFactory.newFactory();
XMLEventReader reader = factory.createXMLEventReader(new FileReader(fileName));
StAXEventBuilder builder = new StAXEventBuilder();
document = builder.build(reader);
}
catch (JDOMException | IOException | XMLStreamException e)
{
e.printStackTrace();
}
return document;
}
private static Document getDOMParsedDocument(final String fileName)
{
Document document = null;
try
{
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
//If want to make namespace aware.
//factory.setNamespaceAware(true);
DocumentBuilder documentBuilder = factory.newDocumentBuilder();
org.w3c.dom.Document w3cDocument = documentBuilder.parse(fileName);
document = new DOMBuilder().build(w3cDocument);
}
catch (IOException | SAXException | ParserConfigurationException e)
{
e.printStackTrace();
}
return document;
}
/*private static String readFileContent(String filePath)
{
StringBuilder contentBuilder = new StringBuilder();
try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8))
{
stream.forEach(s -> contentBuilder.append(s).append("\n"));
}
catch (IOException e)
{
e.printStackTrace();
}
return contentBuilder.toString();
}*/
}
输出：
Root Element :: employees ================================= Id : 101 FirstName : Lokesh LastName : Gupta country : India Department Id : 25 Department Name : ITS Id : 102 FirstName : Brian LastName : Schultz country : USA Department Id : 26 Department Name : DEV ================================= Employee Ids :: 101 Employee Ids :: 102 Employee First Name :: Lokesh Employee First Name :: Brian
快乐学习！！
参考：
地址：https://www.cundage.com/article/jdom2-read-parse-xml-examples.html
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