import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.StringReader;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;


// 格式化
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
Document document = documentBuilder.parse(new InputSource(new StringReader(xml)));
ByteArrayOutputStream out = new ByteArrayOutputStream();
pretty(document, out, 4);
String finalString = new String(out.toByteArray());

/**
* XML格式化.
* 
* @param document
*            输入Doc
* @param outputStream
*            输出流
* @param indent
*            缩进几个字符
* @throws Exception
*/
private static void pretty(Document document, OutputStream outputStream, int indent) throws Exception {
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
    if (indent > 0) {
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", Integer.toString(indent));
    }
    Result result = new StreamResult(outputStream);
    Source source = new DOMSource(document);
    transformer.transform(source, result);
}