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
为了将来的参考，这里有一个对我有用的解决方案(感谢@George Hawkins在其中一个答案中发表的评论):
DOMImplementationRegistry registry = DOMImplementationRegistry.newInstance();
DOMImplementationLS impl = (DOMImplementationLS) registry.getDOMImplementation("LS");
LSSerializer writer = impl.createLSSerializer();
writer.getDomConfig().setParameter("format-pretty-print", Boolean.TRUE);
LSOutput output = impl.createLSOutput();
ByteArrayOutputStream out = new ByteArrayOutputStream();
output.setByteStream(out);
writer.write(document, output);
String xmlStr = new String(out.toByteArray());
其他回答
基于这个答案的一个更简单的解决方案:
public static String prettyFormat(String input, int indent) {
try {
Source xmlInput = new StreamSource(new StringReader(input));
StringWriter stringWriter = new StringWriter();
StreamResult xmlOutput = new StreamResult(stringWriter);
TransformerFactory transformerFactory = TransformerFactory.newInstance();
transformerFactory.setAttribute("indent-number", indent);
transformerFactory.setAttribute(XMLConstants.ACCESS_EXTERNAL_DTD, "");
transformerFactory.setAttribute(XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "");
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.transform(xmlInput, xmlOutput);
return xmlOutput.getWriter().toString();
} catch (Exception e) {
throw new RuntimeException(e); // simple exception handling, please review it
}
}
public static String prettyFormat(String input) {
return prettyFormat(input, 2);
}
testcase:
prettyFormat("<root><child>aaa</child><child/></root>");
返回:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<child>aaa</child>
<child/>
</root>
//忽略:原始编辑只需要在代码中的类名中缺少s。为了在SO上获得超过6个字符的验证，添加了多余的6个字符
这是我自己问题的答案。我将各种结果的答案结合起来，编写了一个输出XML的类。
不保证它如何响应无效的XML或大型文档。
package ecb.sdw.pretty;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
/**
* 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 XmlFormatter() {
}
public String format(String unformattedXml) {
try {
final Document document = parseXmlFile(unformattedXml);
OutputFormat format = new OutputFormat(document);
format.setLineWidth(65);
format.setIndenting(true);
format.setIndent(2);
Writer out = new StringWriter();
XMLSerializer serializer = new XMLSerializer(out, format);
serializer.serialize(document);
return out.toString();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
private Document parseXmlFile(String in) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource(new StringReader(in));
return db.parse(is);
} catch (ParserConfigurationException e) {
throw new RuntimeException(e);
} catch (SAXException e) {
throw new RuntimeException(e);
} catch (IOException 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));
}
}
我总是使用下面的函数:
public static String prettyPrintXml(String xmlStringToBeFormatted) {
String formattedXmlString = null;
try {
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
documentBuilderFactory.setValidating(true);
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
InputSource inputSource = new InputSource(new StringReader(xmlStringToBeFormatted));
Document document = documentBuilder.parse(inputSource);
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
StreamResult streamResult = new StreamResult(new StringWriter());
DOMSource dOMSource = new DOMSource(document);
transformer.transform(dOMSource, streamResult);
formattedXmlString = streamResult.getWriter().toString().trim();
} catch (Exception ex) {
StringWriter sw = new StringWriter();
ex.printStackTrace(new PrintWriter(sw));
System.err.println(sw.toString());
}
return formattedXmlString;
}
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;
}
}
}
下面的代码工作得很好
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
String formattedXml1 = prettyFormat("<root><child>aaa</child><child/></root>");
public static String prettyFormat(String input) {
return prettyFormat(input, "2");
}
public static String prettyFormat(String input, String indent) {
Source xmlInput = new StreamSource(new StringReader(input));
StringWriter stringWriter = new StringWriter();
try {
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", indent);
transformer.transform(xmlInput, new StreamResult(stringWriter));
String pretty = stringWriter.toString();
pretty = pretty.replace("\r\n", "\n");
return pretty;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
