U retain doctype when prettifying xml

Author: fvarrui

src/main/java/io/github/fvarrui/javapackager/utils/XMLUtils.java

@@ -11,6 +11,7 @@
 import javax.xml.transform.stream.StreamResult;
 
 import org.w3c.dom.Document;
+import org.w3c.dom.DocumentType;
 import org.w3c.dom.Node;
 import org.w3c.dom.NodeList;
 
@@ -29,13 +30,20 @@ public static final void prettify(File file) throws Exception {
 		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
 		DocumentBuilder builder = factory.newDocumentBuilder();
 		Document document = builder.parse(file);
-
+		
 		trimWhitespace(document);
 
 		Transformer transformer = TransformerFactory.newInstance().newTransformer();
 		transformer.setOutputProperty(OutputKeys.INDENT, "yes");
+		transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
 		transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
-		transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC,"yes");			
+
+        DocumentType doctype = document.getDoctype();
+        if(doctype != null) {
+            transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, doctype.getPublicId());
+            transformer.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, doctype.getSystemId());
+        }		
+		
 		transformer.transform(new DOMSource(document), new StreamResult(file));
 
 	}