java生成xml文件

在Java中可以使用DOM或者SAX来生成XML文件，下面分别介绍使用这两种方式生成XML文件的方法。

1. 使用DOM生成XML文件

DOM方式是将整个XML文件读入内存中，然后以树形结构进行操作。下面是使用DOM方式生成XML文件的示例代码：

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class GenerateXML {

    public static void main(String[] args) {

        try {

            DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder docBuilder = docFactory.newDocumentBuilder();

            // 创建根节点
            Document doc = docBuilder.newDocument();
            Element rootElement = doc.createElement("employees");
            doc.appendChild(rootElement);

            // 创建子节点
            Element employee = doc.createElement("employee");
            rootElement.appendChild(employee);

            // 设置子节点属性
            employee.setAttribute("id", "1");

            // 创建子节点
            Element firstName = doc.createElement("firstName");
            firstName.appendChild(doc.createTextNode("John"));
            employee.appendChild(firstName);

            // 创建子节点
            Element lastName = doc.createElement("lastName");
            lastName.appendChild(doc.createTextNode("Doe"));
            employee.appendChild(lastName);

            // 创建子节点
            Element age = doc.createElement("age");
            age.appendChild(doc.createTextNode("30"));
            employee.appendChild(age);

            // 创建子节点
            Element gender = doc.createElement("gender");
            gender.appendChild(doc.createTextNode("Male"));
            employee.appendChild(gender);

            // 创建TransformerFactory对象
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            DOMSource source = new DOMSource(doc);

            // 将XML文件写入磁盘
            StreamResult result = new StreamResult(new File("employees.xml"));

            transformer.transform(source, result);

            System.out.println("XML文件生成成功！");

        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (TransformerException e) {
            e.printStackTrace();
        }
    }
}

运行该程序后，会在当前目录下生成一个名为employees.xml的XML文件，内容如下：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<employees>
    <employee id="1">
        <firstName>John</firstName>
        <lastName>Doe</lastName>
        <age>30</age>
        <gender>Male</gender>
    </employee>
</employees>

2. 使用SAX生成XML文件

SAX方式是一种基于事件驱动的XML解析方式，它不需要将整个XML文件读入内存中，而是在解析XML文件时逐个读取XML元素，以达到节省内存的目的。下面是使用SAX方式生成XML文件的示例代码：

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

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 GenerateXML {

    public static void main(String[] args) {

        try {

            // 创建一个SAXParserFactory实例
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser saxParser = factory.newSAXParser();

            // 创建一个DefaultHandler实例
            DefaultHandler handler = new DefaultHandler() {

                boolean bFirstName = false;
                boolean bLastName = false;
                boolean bAge = false;
                boolean bGender = false;

                // 开始解析XML元素时调用该方法
                public void startElement(String uri, String localName, String qName, Attributes attributes)
                        throws SAXException {

                    if (qName.equalsIgnoreCase("employee")) {
                        System.out.println("开始解析员工信息");
                    } else if (qName.equalsIgnoreCase("firstName")) {
                        bFirstName = true;
                    } else if (qName.equalsIgnoreCase("lastName")) {
                        bLastName = true;
                    } else if (qName.equalsIgnoreCase("age")) {
                        bAge = true;
                    } else if (qName.equalsIgnoreCase("gender")) {
                        bGender = true;
                    }

                }

                // 解析XML元素时获取元素内容时调用该方法
                public void characters(char ch[], int start, int length) throws SAXException {

                    if (bFirstName) {
                        System.out.println("员工名：" + new String(ch, start, length));
                        bFirstName = false;
                    } else if (bLastName) {
                        System.out.println("员工姓：" + new String(ch, start, length));
                        bLastName = false;
                    } else if (bAge) {
                        System.out.println("员工年龄：" + new String(ch, start, length));
                        bAge = false;
                    } else if (bGender) {
                        System.out.println("员工性别：" + new String(ch, start, length));
                        bGender = false;
                    }

                }

                // 结束解析XML元素时调用该方法
                public void endElement(String uri, String localName, String qName) throws SAXException {

                    if (qName.equalsIgnoreCase("employee")) {
                        System.out.println("结束解析员工信息");
                    }
                }

            };

            // 开始解析XML文件
            saxParser.parse(new File("employees.xml"), handler);

            // 将XML文件写入磁盘
            FileWriter writer = new FileWriter("employees2.xml");
            writer.write("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n");
            writer.write("<employees>\n");
            writer.write("<employee>\n");
            writer.write("<firstName>John</firstName>\n");
            writer.write("<lastName>Doe</lastName>\n");
            writer.write("<age>30</age>\n");
            writer.write("<gender>Male</gender>\n");
            writer.write("</employee>\n");
            writer.write("</employees>\n");
            writer.close();

            System.out.println("XML文件生成成功！");

        } catch (SAXException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

运行该程序后，会在当前目录下生成一个名为employees2.xml的XML文件，内容如下：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<employees>
    <employee>
        <firstName>John</firstName>
        <lastName>Doe</lastName>
        <age>30</age>
        <gender>Male</gender>
    </employee>
</employees>