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>
在提出我自己的解决方案之前,我应该先看看这一页!不管怎样,我使用Java递归来解析xml页面。此代码是完全自包含的,不依赖于第三方库。也. .它使用递归!
// you call this method passing in the xml text
public static void prettyPrint(String text){
prettyPrint(text, 0);
}
// "index" corresponds to the number of levels of nesting and/or the number of tabs to print before printing the tag
public static void prettyPrint(String xmlText, int index){
boolean foundTagStart = false;
StringBuilder tagChars = new StringBuilder();
String startTag = "";
String endTag = "";
String[] chars = xmlText.split("");
// find the next start tag
for(String ch : chars){
if(ch.equalsIgnoreCase("<")){
tagChars.append(ch);
foundTagStart = true;
} else if(ch.equalsIgnoreCase(">") && foundTagStart){
startTag = tagChars.append(ch).toString();
String tempTag = startTag;
endTag = (tempTag.contains("\"") ? (tempTag.split(" ")[0] + ">") : tempTag).replace("<", "</"); // <startTag attr1=1 attr2=2> => </startTag>
break;
} else if(foundTagStart){
tagChars.append(ch);
}
}
// once start and end tag are calculated, print start tag, then content, then end tag
if(foundTagStart){
int startIndex = xmlText.indexOf(startTag);
int endIndex = xmlText.indexOf(endTag);
// handle if matching tags NOT found
if((startIndex < 0) || (endIndex < 0)){
if(startIndex < 0) {
// no start tag found
return;
} else {
// start tag found, no end tag found (handles single tags aka "<mytag/>" or "<?xml ...>")
printTabs(index);
System.out.println(startTag);
// move on to the next tag
// NOTE: "index" (not index+1) because next tag is on same level as this one
prettyPrint(xmlText.substring(startIndex+startTag.length(), xmlText.length()), index);
return;
}
// handle when matching tags found
} else {
String content = xmlText.substring(startIndex+startTag.length(), endIndex);
boolean isTagContainsTags = content.contains("<"); // content contains tags
printTabs(index);
if(isTagContainsTags){ // ie: <tag1><tag2>stuff</tag2></tag1>
System.out.println(startTag);
prettyPrint(content, index+1); // "index+1" because "content" is nested
printTabs(index);
} else {
System.out.print(startTag); // ie: <tag1>stuff</tag1> or <tag1></tag1>
System.out.print(content);
}
System.out.println(endTag);
int nextIndex = endIndex + endTag.length();
if(xmlText.length() > nextIndex){ // if there are more tags on this level, continue
prettyPrint(xmlText.substring(nextIndex, xmlText.length()), index);
}
}
} else {
System.out.print(xmlText);
}
}
private static void printTabs(int counter){
while(counter-- > 0){
System.out.print("\t");
}
}
I have found that in Java 1.6.0_32 the normal method to pretty print an XML string (using a Transformer with a null or identity xslt) does not behave as I would like if tags are merely separated by whitespace, as opposed to having no separating text. I tried using <xsl:strip-space elements="*"/> in my template to no avail. The simplest solution I found was to strip the space the way I wanted using a SAXSource and XML filter. Since my solution was for logging I also extended this to work with incomplete XML fragments. Note the normal method seems to work fine if you use a DOMSource but I did not want to use this because of the incompleteness and memory overhead.
public static class WhitespaceIgnoreFilter extends XMLFilterImpl
{
@Override
public void ignorableWhitespace(char[] arg0,
int arg1,
int arg2) throws SAXException
{
//Ignore it then...
}
@Override
public void characters( char[] ch,
int start,
int length) throws SAXException
{
if (!new String(ch, start, length).trim().equals(""))
super.characters(ch, start, length);
}
}
public static String prettyXML(String logMsg, boolean allowBadlyFormedFragments) throws SAXException, IOException, TransformerException
{
TransformerFactory transFactory = TransformerFactory.newInstance();
transFactory.setAttribute("indent-number", new Integer(2));
Transformer transformer = transFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
StringWriter out = new StringWriter();
XMLReader masterParser = SAXHelper.getSAXParser(true);
XMLFilter parser = new WhitespaceIgnoreFilter();
parser.setParent(masterParser);
if(allowBadlyFormedFragments)
{
transformer.setErrorListener(new ErrorListener()
{
@Override
public void warning(TransformerException exception) throws TransformerException
{
}
@Override
public void fatalError(TransformerException exception) throws TransformerException
{
}
@Override
public void error(TransformerException exception) throws TransformerException
{
}
});
}
try
{
transformer.transform(new SAXSource(parser, new InputSource(new StringReader(logMsg))), new StreamResult(out));
}
catch (TransformerException e)
{
if(e.getCause() != null && e.getCause() instanceof SAXParseException)
{
if(!allowBadlyFormedFragments || !"XML document structures must start and end within the same entity.".equals(e.getCause().getMessage()))
{
throw e;
}
}
else
{
throw e;
}
}
out.flush();
return out.toString();
}
除了max、codeskrap、David Easley和milosmns给出的答案外,还可以看看我的轻量级、高性能漂亮打印机库:xml-formatter
// construct lightweight, threadsafe, instance
PrettyPrinter prettyPrinter = PrettyPrinterBuilder.newPrettyPrinter().build();
StringBuilder buffer = new StringBuilder();
String xml = ..; // also works with char[] or Reader
if(prettyPrinter.process(xml, buffer)) {
// valid XML, print buffer
} else {
// invalid XML, print xml
}
有时,就像直接从文件运行模拟SOAP服务时,有一个漂亮的打印机也能处理已经打印好的XML是很好的:
PrettyPrinter prettyPrinter = PrettyPrinterBuilder.newPrettyPrinter().ignoreWhitespace().build();
正如一些人评论的那样,漂亮打印只是一种以更适合人类阅读的形式表示XML的方法——严格来说,XML数据中不应该有空格。
该库用于日志记录的漂亮打印,还包括用于过滤(子树移除/匿名化)和漂亮打印CDATA和Text节点中的XML的函数。