我有一个包含XML的Java字符串,没有换行或缩进。我想把它变成一个字符串与格式良好的XML。我怎么做呢?

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。输出是一个字符串。

(基本)模拟结果:

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

当前回答

对于那些寻找快速和肮脏的解决方案的人——它不需要XML是100%有效的。例如,在REST / SOAP日志的情况下(你永远不知道其他人发送了什么;-))

我发现并改进了一个我在网上找到的代码剪辑,我认为这仍然是一个有效的可能的方法:

public static String prettyPrintXMLAsString(String xmlString) {
    /* Remove new lines */
    final String LINE_BREAK = "\n";
    xmlString = xmlString.replaceAll(LINE_BREAK, "");
    StringBuffer prettyPrintXml = new StringBuffer();
    /* Group the xml tags */
    Pattern pattern = Pattern.compile("(<[^/][^>]+>)?([^<]*)(</[^>]+>)?(<[^/][^>]+/>)?");
    Matcher matcher = pattern.matcher(xmlString);
    int tabCount = 0;
    while (matcher.find()) {
        String str1 = (null == matcher.group(1) || "null".equals(matcher.group())) ? "" : matcher.group(1);
        String str2 = (null == matcher.group(2) || "null".equals(matcher.group())) ? "" : matcher.group(2);
        String str3 = (null == matcher.group(3) || "null".equals(matcher.group())) ? "" : matcher.group(3);
        String str4 = (null == matcher.group(4) || "null".equals(matcher.group())) ? "" : matcher.group(4);

        if (matcher.group() != null && !matcher.group().trim().equals("")) {
            printTabs(tabCount, prettyPrintXml);
            if (!str1.equals("") && str3.equals("")) {
                ++tabCount;
            }
            if (str1.equals("") && !str3.equals("")) {
                --tabCount;
                prettyPrintXml.deleteCharAt(prettyPrintXml.length() - 1);
            }

            prettyPrintXml.append(str1);
            prettyPrintXml.append(str2);
            prettyPrintXml.append(str3);
            if (!str4.equals("")) {
                prettyPrintXml.append(LINE_BREAK);
                printTabs(tabCount, prettyPrintXml);
                prettyPrintXml.append(str4);
            }
            prettyPrintXml.append(LINE_BREAK);
        }
    }
    return prettyPrintXml.toString();
}

private static void printTabs(int count, StringBuffer stringBuffer) {
    for (int i = 0; i < count; i++) {
        stringBuffer.append("\t");
    }
}

public static void main(String[] args) {
    String x = new String(
            "<soap:Envelope xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\"><soap:Body><soap:Fault><faultcode>soap:Client</faultcode><faultstring>INVALID_MESSAGE</faultstring><detail><ns3:XcbSoapFault xmlns=\"\" xmlns:ns3=\"http://www.someapp.eu/xcb/types/xcb/v1\"><CauseCode>20007</CauseCode><CauseText>INVALID_MESSAGE</CauseText><DebugInfo>Problems creating SAAJ object model</DebugInfo></ns3:XcbSoapFault></detail></soap:Fault></soap:Body></soap:Envelope>");
    System.out.println(prettyPrintXMLAsString(x));
}

输出如下:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <soap:Fault>
        <faultcode>soap:Client</faultcode>
        <faultstring>INVALID_MESSAGE</faultstring>
        <detail>
            <ns3:XcbSoapFault xmlns="" xmlns:ns3="http://www.someapp.eu/xcb/types/xcb/v1">
                <CauseCode>20007</CauseCode>
                <CauseText>INVALID_MESSAGE</CauseText>
                <DebugInfo>Problems creating SAAJ object model</DebugInfo>
            </ns3:XcbSoapFault>
        </detail>
    </soap:Fault>
  </soap:Body>
</soap:Envelope>

其他回答

请注意,排名靠前的答案需要使用xerces。

如果您不想添加这个外部依赖,那么您可以简单地使用标准jdk库(实际上是在内部使用xerces构建的)。

注意:jdk 1.5版本有一个bug,请参阅http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6296446,但现在已经解决了。

(注意,如果发生错误,将返回原始文本)

package com.test;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.stream.StreamResult;

import org.xml.sax.InputSource;

public class XmlTest {
    public static void main(String[] args) {
        XmlTest t = new XmlTest();
        System.out.println(t.formatXml("<a><b><c/><d>text D</d><e value='0'/></b></a>"));
    }

    public String formatXml(String xml){
        try{
            Transformer serializer= SAXTransformerFactory.newInstance().newTransformer();
            serializer.setOutputProperty(OutputKeys.INDENT, "yes");
            //serializer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            serializer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
            //serializer.setOutputProperty("{http://xml.customer.org/xslt}indent-amount", "2");
            Source xmlSource=new SAXSource(new InputSource(new ByteArrayInputStream(xml.getBytes())));
            StreamResult res =  new StreamResult(new ByteArrayOutputStream());            
            serializer.transform(xmlSource, res);
            return new String(((ByteArrayOutputStream)res.getOutputStream()).toByteArray());
        }catch(Exception e){
            //TODO log error
            return xml;
        }
    }

}

只是另一种适合我们的解决方法

import java.io.StringWriter;
import org.dom4j.DocumentHelper;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.XMLWriter;

**
 * Pretty Print XML String
 * 
 * @param inputXmlString
 * @return
 */
public static String prettyPrintXml(String xml) {

    final StringWriter sw;

    try {
        final OutputFormat format = OutputFormat.createPrettyPrint();
        final org.dom4j.Document document = DocumentHelper.parseText(xml);
        sw = new StringWriter();
        final XMLWriter writer = new XMLWriter(sw, format);
        writer.write(document);
    }
    catch (Exception e) {
        throw new RuntimeException("Error pretty printing xml:\n" + xml, e);
    }
    return sw.toString();
}

使用scala:

import xml._
val xml = XML.loadString("<tag><nested>hello</nested></tag>")
val formatted = new PrettyPrinter(150, 2).format(xml)
println(formatted)

如果你依赖scala-library.jar,你也可以在Java中这样做。它是这样的:

import scala.xml.*;

public class FormatXML {
    public static void main(String[] args) {
        String unformattedXml = "<tag><nested>hello</nested></tag>";
        PrettyPrinter pp = new PrettyPrinter(150, 3);
        String formatted = pp.format(XML.loadString(unformattedXml), TopScope$.MODULE$);
        System.out.println(formatted);
    }
}

PrettyPrinter对象是用两个整数构造的,第一个是最大行长,第二个是缩进步骤。

有一个非常好的命令行XML实用程序叫做xmlstarlet(http://xmlstar.sourceforge.net/),它可以做很多事情,很多人都在使用它。

您可以使用Runtime以编程方式执行此程序。然后读入格式化的输出文件。它具有比几行Java代码所能提供的更多选项和更好的错误报告。

下载xmlstarlet: http://sourceforge.net/project/showfiles.php?group_id=66612&package_id=64589

如果您确信您有一个有效的XML,那么这个很简单,并且避免了XML DOM树。可能有一些错误,如果你看到任何错误,请评论

public String prettyPrint(String xml) {
            if (xml == null || xml.trim().length() == 0) return "";

            int stack = 0;
            StringBuilder pretty = new StringBuilder();
            String[] rows = xml.trim().replaceAll(">", ">\n").replaceAll("<", "\n<").split("\n");

            for (int i = 0; i < rows.length; i++) {
                    if (rows[i] == null || rows[i].trim().length() == 0) continue;

                    String row = rows[i].trim();
                    if (row.startsWith("<?")) {
                            // xml version tag
                            pretty.append(row + "\n");
                    } else if (row.startsWith("</")) {
                            // closing tag
                            String indent = repeatString("    ", --stack);
                            pretty.append(indent + row + "\n");
                    } else if (row.startsWith("<")) {
                            // starting tag
                            String indent = repeatString("    ", stack++);
                            pretty.append(indent + row + "\n");
                    } else {
                            // tag data
                            String indent = repeatString("    ", stack);
                            pretty.append(indent + row + "\n");
                    }
            }

            return pretty.toString().trim();
    }