如何从 Java 漂亮地打印 XML？

Question

我有一个包含 XML 的 Java 字符串，没有换行符或缩进。我想把它变成一个格式很好的 XML 的字符串。我该怎么做呢？

 String unformattedXml = "<tag><nested>hello</nested></tag>";
String formattedXml = new [UnknownClass]().format(unformattedXml);

注意：我的输入是 String 。我的输出是一个 String 。

（基本）模拟结果：

 <?xml version="1.0" encoding="UTF-8"?>
<root>
  <tag>
    <nested>hello</nested>
  </tag>
</root>

原文由 Steve McLeod 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

现在是 2012 年，Java 可以比以前使用 XML 做更多的事情，我想为我接受的答案添加一个替代方案。这在 Java 6 之外没有依赖关系。

 import org.w3c.dom.Node;
import org.w3c.dom.bootstrap.DOMImplementationRegistry;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSSerializer;
import org.xml.sax.InputSource;

import javax.xml.parsers.DocumentBuilderFactory;
import java.io.StringReader;

/**
 * Pretty-prints xml, supplied as a string.
 * <p/>
 * eg.
 * <code>
 * String formattedXml = new XmlFormatter().format("<tag><nested>hello</nested></tag>");
 * </code>
 */
public class XmlFormatter {

    public String format(String xml) {

        try {
            final InputSource src = new InputSource(new StringReader(xml));
            final Node document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(src).getDocumentElement();
            final Boolean keepDeclaration = Boolean.valueOf(xml.startsWith("<?xml"));

        //May need this: System.setProperty(DOMImplementationRegistry.PROPERTY,"com.sun.org.apache.xerces.internal.dom.DOMImplementationSourceImpl");

            final DOMImplementationRegistry registry = DOMImplementationRegistry.newInstance();
            final DOMImplementationLS impl = (DOMImplementationLS) registry.getDOMImplementation("LS");
            final LSSerializer writer = impl.createLSSerializer();

            writer.getDomConfig().setParameter("format-pretty-print", Boolean.TRUE); // Set this to true if the output needs to be beautified.
            writer.getDomConfig().setParameter("xml-declaration", keepDeclaration); // Set this to true if the declaration is needed to be outputted.

            return writer.writeToString(document);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) {
        String unformattedXml =
                "<?xml version=\"1.0\" encoding=\"UTF-8\"?><QueryMessage\n" +
                        "        xmlns=\"http://www.SDMX.org/resources/SDMXML/schemas/v2_0/message\"\n" +
                        "        xmlns:query=\"http://www.SDMX.org/resources/SDMXML/schemas/v2_0/query\">\n" +
                        "    <Query>\n" +
                        "        <query:CategorySchemeWhere>\n" +
                        "   \t\t\t\t\t         <query:AgencyID>ECB\n\n\n\n</query:AgencyID>\n" +
                        "        </query:CategorySchemeWhere>\n" +
                        "    </Query>\n\n\n\n\n" +
                        "</QueryMessage>";

        System.out.println(new XmlFormatter().format(unformattedXml));
    }
}

原文由 Steve McLeod 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
// initialize StreamResult with File object to save to file
StreamResult result = new StreamResult(new StringWriter());
DOMSource source = new DOMSource(doc);
transformer.transform(source, result);
String xmlString = result.getWriter().toString();
System.out.println(xmlString);

注意：结果可能因 Java 版本而异。搜索特定于您的平台的解决方法。

原文由 Lorenzo Boccaccia 发布，翻译遵循 CC BY-SA 4.0 许可协议