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
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:根据Java版本的不同，结果可能有所不同。搜索特定于您的平台的解决方案。
其他回答
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:根据Java版本的不同，结果可能有所不同。搜索特定于您的平台的解决方案。
嗯…面对这样的事情，这是一个已知的bug… 只需添加这个OutputProperty ..
transformer.setOutputProperty(OutputPropertiesFactory.S_KEY_INDENT_AMOUNT, "8");
希望这对你有所帮助……
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());
Since you are starting with a String, you can convert to a DOM object (e.g. Node) before you use the Transformer. However, if you know your XML string is valid, and you don't want to incur the memory overhead of parsing a string into a DOM, then running a transform over the DOM to get a string back - you could just do some old fashioned character by character parsing. Insert a newline and spaces after every </...> characters, keep and indent counter (to determine the number of spaces) that you increment for every <...> and decrement for every </...> you see.
免责声明-我对下面的函数做了剪切/粘贴/文本编辑，所以它们可能不能按原样编译。
public static final Element createDOM(String strXML)
throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating(true);
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource sourceXML = new InputSource(new StringReader(strXML));
Document xmlDoc = db.parse(sourceXML);
Element e = xmlDoc.getDocumentElement();
e.normalize();
return e;
}
public static final void prettyPrint(Node xml, OutputStream out)
throws TransformerConfigurationException, TransformerFactoryConfigurationError, TransformerException {
Transformer tf = TransformerFactory.newInstance().newTransformer();
tf.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
tf.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
tf.setOutputProperty(OutputKeys.INDENT, "yes");
tf.transform(new DOMSource(xml), new StreamResult(out));
}
如果使用第三方XML库是可行的，那么您可以使用一些比目前票数最高的答案所建议的要简单得多的方法。
它声明输入和输出都应该是字符串，所以这里有一个实用程序方法，用XOM库实现:
import nu.xom.*;
import java.io.*;
[...]
public static String format(String xml) throws ParsingException, IOException {
ByteArrayOutputStream out = new ByteArrayOutputStream();
Serializer serializer = new Serializer(out);
serializer.setIndent(4); // or whatever you like
serializer.write(new Builder().build(xml, ""));
return out.toString("UTF-8");
}
我对它进行了测试，结果不依赖于JRE版本或类似的东西。要了解如何根据自己的喜好定制输出格式，请查看Serializer API。
这实际上比我想象的要长——需要一些额外的行，因为Serializer想要写入一个OutputStream。但是请注意，这里很少有用于实际XML处理的代码。
(这个答案是我对XOM的评估的一部分，在我关于替代dom4j的最佳Java XML库的问题中，XOM被建议作为一个选项。在dom4j中，您可以使用XMLWriter和OutputFormat轻松实现这一点。编辑:…正如mlo55的答案所示。)
