如何从 Java 漂亮地打印 XML? [英] How to pretty print XML from Java?

问题描述

我有一个包含 XML 的 Java 字符串，没有换行符或缩进.我想将其转换为具有格式良好的 XML 的字符串.我该怎么做?

I have a Java String that contains XML, with no line feeds or indentations. I would like to turn it into a String with nicely formatted XML. How do I do this?

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

注意:我的输入是一个字符串.我的输出是一个字符串.

Note: My input is a String. My output is a String.

(基本)模拟结果:

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

推荐答案

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 之外没有任何依赖项.

Now it's 2012 and Java can do more than it used to with XML, I'd like to add an alternative to my accepted answer. This has no dependencies outside of Java 6.

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
" +
                        "        xmlns="http://www.SDMX.org/resources/SDMXML/schemas/v2_0/message"
" +
                        "        xmlns:query="http://www.SDMX.org/resources/SDMXML/schemas/v2_0/query">
" +
                        "    <Query>
" +
                        "        <query:CategorySchemeWhere>
" +
                        "   					         <query:AgencyID>ECB



</query:AgencyID>
" +
                        "        </query:CategorySchemeWhere>
" +
                        "    </Query>




" +
                        "</QueryMessage>";

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

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