我有一个包含XML代码的Java字符串，其中没有换行或缩进。我想将其转换为格式良好的XML字符串。如何做到这一点？
String unformattedXml = "<tag><nested>hello</nested></tag>";
String formattedXml = new [UnknownClass]().format(unformattedXml);
<?xml version="1.0" encoding="UTF-8"?>
<root>
<tag>
<nested>hello</nested>
</tag>
</root>
String leastPrettifiedXml = uglyXml.replaceAll("><", ">\n<");
代码很好，只是因为缺少缩进而导致结果不够清晰。
（对于带有缩进的解决方案，请参见其他答案。）
在想出自己的解决方案之前，我应该先查找这个页面！无论如何，我的解决方案使用Java递归来解析xml页面。这段代码完全自包含，不依赖于第三方库。而且..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");
}
}
试试这个：
try
{
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transformer = null;
transformer = transFactory.newTransformer();
StringWriter buffer = new StringWriter();
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.transform(new DOMSource(element),
new StreamResult(buffer));
String str = buffer.toString();
System.out.println("XML INSIDE IS #########################################"+str);
return element;
}
catch (TransformerConfigurationException e)
{
e.printStackTrace();
}
catch (TransformerException e)
{
e.printStackTrace();
}
我曾试图实现类似的功能，但没有任何外部依赖。该应用程序已经使用DOM仅用于记录XML格式！
这是我的示例片段：
public void formatXML(final String unformattedXML) {
final int length = unformattedXML.length();
final int indentSpace = 3;
final StringBuilder newString = new StringBuilder(length + length / 10);
final char space = ' ';
int i = 0;
int indentCount = 0;
char currentChar = unformattedXML.charAt(i++);
char previousChar = currentChar;
boolean nodeStarted = true;
newString.append(currentChar);
for (; i < length - 1;) {
currentChar = unformattedXML.charAt(i++);
if(((int) currentChar < 33) && !nodeStarted) {
continue;
}
switch (currentChar) {
case '<':
if ('>' == previousChar && '/' != unformattedXML.charAt(i - 1) && '/' != unformattedXML.charAt(i) && '!' != unformattedXML.charAt(i)) {
indentCount++;
}
newString.append(System.lineSeparator());
for (int j = indentCount * indentSpace; j > 0; j--) {
newString.append(space);
}
newString.append(currentChar);
nodeStarted = true;
break;
case '>':
newString.append(currentChar);
nodeStarted = false;
break;
case '/':
if ('<' == previousChar || '>' == unformattedXML.charAt(i)) {
indentCount--;
}
newString.append(currentChar);
break;
default:
newString.append(currentChar);
}
previousChar = currentChar;
}
newString.append(unformattedXML.charAt(length - 1));
System.out.println(newString.toString());
}