java 生成xml文件

在Java编程中，生成XML（eXtensible Markup Language）文件是一项常见的任务，尤其是在数据交换、配置存储或报告生成等领域。XML是一种结构化数据格式，它以易于人类阅读和机器解析的方式存储信息。本篇文章将深入探讨如何使用Java来创建XML文件。 1. DOM（Document Object Model）方式： DOM模型将整个XML文档加载到内存中，形成一个树形结构，允许开发者通过节点操作来构建和修改XML。以下是一个简单的示例： ```java import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.InputSource; import java.io.StringReader; import java.io.StringWriter; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; public class GenXml { public static void main(String[] args) throws Exception { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document doc = builder.newDocument(); // 创建根元素 Element rootElement = doc.createElement("Employees"); doc.appendChild(rootElement); // 添加子元素 for (int i = 0; i < 5; i++) { Element employee = doc.createElement("Employee"); rootElement.appendChild(employee); employee.setAttribute("id", String.valueOf(i + 1)); Element name = doc.createElement("Name"); name.setTextContent("Employee " + (i + 1)); employee.appendChild(name); } // 输出XML TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); StringWriter writer = new StringWriter(); transformer.transform(new DOMSource(doc), new StreamResult(writer)); System.out.println(writer.getBuffer().toString().trim()); } } ``` 2. SAX（Simple API for XML）方式： 相比DOM，SAX是事件驱动的，不将整个XML文档加载到内存，而是逐行读取并触发事件回调。这种方式适合处理大型XML文档，但编程相对复杂： ```java import org.xml.sax.Attributes; import org.xml.sax.ContentHandler; import org.xml.sax.SAXException; import org.xml.sax.XMLWriter; import org.xml.sax.helpers.DefaultHandler; import org.xml.sax.helpers.XMLWriterHelper; import javax.xml.transform.OutputKeys; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.sax.SAXTransformerFactory; import javax.xml.transform.stream.StreamResult; import java.io.FileWriter; import java.io.Writer; public class SaxGenXml extends DefaultHandler implements ContentHandler { private XMLWriter xmlWriter; public void startDocument() throws SAXException { SAXTransformerFactory tf = (SAXTransformerFactory) TransformerFactory.newInstance(); try { Transformer serializer = tf.newTransformer(); serializer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); serializer.setOutputProperty(OutputKeys.INDENT, "yes"); Writer out = new FileWriter("output.xml"); xmlWriter = new XMLWriter(out, XMLWriterHelper.createOutputFormat()); xmlWriter.startDocument(); } catch (Exception e) { throw new SAXException(e); } } @Override public void startElement(String uri, String localName, String qName, Attributes atts) throws SAXException { xmlWriter.startElement(uri, localName, qName); for (int i = 0; i < atts.getLength(); i++) { xmlWriter.attribute(atts.getQName(i), atts.getValue(i)); } } @Override public void characters(char[] ch, int start, int length) throws SAXException { xmlWriter.characters(ch, start, length); } @Override public void endElement(String uri, String localName, String qName) throws SAXException { xmlWriter.endElement(uri, localName, qName); } @Override public void endDocument() throws SAXException { xmlWriter.endDocument(); xmlWriter.flush(); } public static void main(String[] args) { try { SaxGenXml handler = new SaxGenXml(); // 这里添加解析逻辑 } catch (Exception e) { e.printStackTrace(); } } } ``` 3. JDOM库： JDOM是一个纯Java的XML处理库，提供了更简洁的API来创建和修改XML文档。以下是一个JDOM生成XML的例子： ```java import org.jdom2.Document; import org.jdom2.Element; import org.jdom2.output.Format; import org.jdom2.output.XMLOutputter; public class JDomGenXml { public static void main(String[] args) { Document doc = new Document(); Element root = new Element("Employees"); doc.setRootElement(root); for (int i = 0; i < 5; i++) { Element employee = new Element("Employee"); employee.setAttribute("id", String.valueOf(i + 1)); Element name = new Element("Name"); name.setText("Employee " + (i + 1)); employee.addContent(name); root.addContent(employee); } XMLOutputter outputter = new XMLOutputter(); outputter.setFormat(Format.getPrettyFormat()); System.out.println(outputter.outputString(doc)); try { outputter.output(doc, new FileWriter("output.xml")); } catch (IOException e) { e.printStackTrace(); } } } ``` 4. 使用Java内置的`javax.xml.stream`包（StaX）： StaX是另一种基于流的API，允许程序在解析XML时逐步生成输出。与SAX类似，它不需要将整个文档加载到内存中，但编程接口更友好： ```java import javax.xml.stream.XMLStreamWriter; import javax.xml.stream.XMLOutputFactory; import java.io.FileWriter; import java.io.IOException; public class StaxGenXml { public static void main(String[] args) { XMLOutputFactory factory = XMLOutputFactory.newFactory(); try (XMLStreamWriter writer = factory.createXMLStreamWriter(new FileWriter("output.xml"))) { writer.writeStartDocument("UTF-8", "1.0"); writer.writeStartElement("Employees"); for (int i = 0; i < 5; i++) { writer.writeStartElement("Employee"); writer.writeAttribute("id", String.valueOf(i + 1)); writer.writeStartElement("Name"); writer.writeCharacters("Employee " + (i + 1)); writer.writeEndElement(); // Name writer.writeEndElement(); // Employee } writer.writeEndElement(); // Employees writer.writeEndDocument(); } catch (IOException | XMLStreamException e) { e.printStackTrace(); } } } ``` 总结起来，Java提供多种方式生成XML文件，包括DOM、SAX、JDOM和StaX。选择哪种方法取决于具体需求，如文件大小、性能和编程复杂性等因素。在实际开发中，根据项目需求和性能要求，合理选择并利用这些工具可以有效地完成XML文件的生成任务。