JavaでObjectからXMLを生成して標準出力に書き出す

WriteXML.java

import java.io.StringWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.TransformerConfigurationException;
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.Element;
import org.xml.sax.SAXException;

public class WriteXML {
  public static void main(String... args) {
    List<Person> people = new ArrayList<>();
    people.add(new Person("taro", 20));
    people.add(new Person("hanako", 23));
    people.add(new Person("foobar", 16));

    try (Writer w = new StringWriter()) {
      writeXML(w, people);
      var s = w.toString();
      System.out.println(s);
    } catch (Exception e) {}
  }

  private static void writeXML(Writer writer, List<Person> people)
      throws ParserConfigurationException, TransformerConfigurationException, TransformerException {
    var factory = DocumentBuilderFactory.newInstance();
    var builder = factory.newDocumentBuilder();
    var document = builder.newDocument();
    var root = document.createElement("people");
    document.appendChild(root);
    people.stream()
        .forEach(
            item -> {
              var elem = document.createElement("person");
              elem.setAttribute("name", item.name);
              elem.setAttribute("age", "" + item.age);
              root.appendChild(elem);
            });
    var transformerFactory = TransformerFactory.newInstance();
    var transformer = transformerFactory.newTransformer();
    var domSource = new DOMSource(document);
    var streamResult = new StreamResult(writer);
    transformer.setOutputProperty(OutputKeys.INDENT, "yes");
    transformer.transform(domSource, streamResult);
  }
}

class Person {
  final String name;
  final int age;
  Person(String name, int age) {
    this.name = name;
    this.age = age;
  }
}

z_README.md

前提条件

OpenJDK 16.0.1

実行方法

javac WriteXML.java
java WriteXML

実行結果

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<people>
    <person age="20" name="taro"/>
    <person age="23" name="hanako"/>
    <person age="16" name="foobar"/>
</people>