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
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();
}
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;
}
}
}
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
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");
}
}
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();
}
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
