Added single-tag vs dual-tag distinction to strict parser

src/main/java/net/vhati/modmanager/core/EmptyAwareSAXHandlerFactory.java

@@ -0,0 +1,124 @@
+package net.vhati.modmanager.core;
+
+import org.xml.sax.Attributes;
+import org.xml.sax.Locator;
+import org.xml.sax.SAXException;
+import org.jdom2.Element;
+import org.jdom2.JDOMFactory;
+import org.jdom2.Parent;
+import org.jdom2.Text;
+import org.jdom2.input.sax.SAXHandler;
+import org.jdom2.input.sax.SAXHandlerFactory;
+
+
+/**
+ * A factory that produces SAXHandlers which distinguish tag-pairs from dual tags.
+ *
+ * While this factory is registered with a SAXBuilder, strict parsing
+ * will occur as normal, notifying the SAXHandler of progress. When
+ * the handler hears that a tag ended at a different line/column than
+ * where it started, and no other text was reported along the way, a
+ * zero-length text node will be added as token content.
+ *
+ * Later, when the Element tree is printed, a special
+ * XMLOutputProcessor can reproduce the tag pair pased on the
+ * presence of child Content objects - like the dummy string - rather
+ * than the presence of non-whitespace text after formatting.
+ *
+ * Note: Not all XMLReaders offer a Locator for line/col info. When
+ * that info is not available, this handler will do nothing special.
+ *
+ * @see org.jdom2.input.SAXBuilder#setSAXHandlerFactory(SAXHandlerFactory factory)
+ */
+public class EmptyAwareSAXHandlerFactory implements SAXHandlerFactory {
+
+	@Override
+	public SAXHandler createSAXHandler( JDOMFactory factory ) {
+		return new EmptyAwareSAXHandler( factory );
+	}
+
+
+
+	public static class EmptyAwareSAXHandler extends SAXHandler {
+
+		boolean emptyTag = true;
+		int startTagLine = -1;
+		int startTagColumn = -1;
+
+		public EmptyAwareSAXHandler( JDOMFactory factory ) {
+			super( factory );
+		}
+
+		@Override
+		public void startElement( String namespaceURI, String localName, String qName, Attributes atts ) throws SAXException {
+			emptyTag = true;
+			startTagLine = -1;
+			startTagColumn = -1;
+
+			Locator loc = getDocumentLocator();
+			if ( loc != null ) {
+				startTagLine = loc.getLineNumber();
+				startTagColumn = loc.getColumnNumber();
+			}
+			super.startElement( namespaceURI, localName, qName, atts );
+		}
+
+		@Override
+		public void comment( char[] ch, final int start, final int length ) throws SAXException {
+			emptyTag = false;
+			super.comment( ch, start, length );
+		}
+
+		@Override
+		public void characters( char[] ch, final int start, final int length ) throws SAXException {
+			emptyTag = false;
+			super.characters( ch, start, length );
+		}
+
+		@Override
+		public void ignorableWhitespace( char[] ch, int start, int length) throws SAXException {
+			emptyTag = false;
+			super.characters( ch, start, length );
+		}
+
+		@Override
+		public void processingInstruction( String target, String data ) throws SAXException {
+			super.processingInstruction( target, data );
+		}
+
+		@Override
+		public void startCDATA() {
+			emptyTag = false;
+			super.startCDATA();
+		}
+
+		@Override
+		public void endElement( String namespaceURI, String localName, String qName ) throws SAXException {
+			Element closedElement = getCurrentElement();
+			boolean twoPartTag = false;
+
+			Locator loc = getDocumentLocator();
+			if ( loc != null ) {
+				int endTagLine = loc.getLineNumber();
+				int endTagColumn = loc.getColumnNumber();
+
+				if ( startTagLine != -1 && endTagLine != -1 && startTagLine != endTagLine) {
+					twoPartTag = true;
+				}
+				else if ( startTagColumn != -1 && endTagColumn != -1 && startTagColumn != endTagColumn ) {
+					twoPartTag = true;
+				}
+			}
+
+			super.endElement( namespaceURI, localName, qName );
+
+			if ( emptyTag && twoPartTag && closedElement.getContent().isEmpty() ) {
+				// This is a separate closing tag after an empty value.
+				// Add a blank text node.
+
+				final Text text = getFactory().text( "" );
+				getFactory().addContent( closedElement, text );
+			}
+		}
+	}
+}