Resolve as many StAX unit test fails as possible

Author: rolfl

core/src/java/org/jdom2/input/StAXStreamWriter.java

@@ -460,7 +460,7 @@ public void writeCharacters(final String chars) throws XMLStreamException {
 		if (parent instanceof Element) {
 			if (activetext != null) {
 				activetext.append(chars);
-			} else {
+			} else if (chars.length() > 0) {
 				activetext = factory.text(chars);
 				factory.addContent(parent, activetext);
 			}

test/src/java/org/jdom2/test/cases/output/TestStAXEventOutputter.java

@@ -60,6 +60,14 @@
 
 @SuppressWarnings("javadoc")
 public final class TestStAXEventOutputter extends AbstractTestOutputter {
+	
+	// ******************************************************************************
+	// ******************************************************************************
+	// StAX is really ugly - it breaks SurrogatePair handling with non-UTF8 encoding
+	// As a result, some of these test cases fail in Recent Java versions
+	// - most test*Surrogate*Pair tests.
+	// ******************************************************************************
+	// ******************************************************************************
 
 	private final static XMLOutputFactory soutfactory = XMLOutputFactory.newInstance();
 	private final static XMLInputFactory sinfactory = XMLInputFactory.newInstance();

test/src/java/org/jdom2/test/cases/output/TestStAXReader2Writer.java

@@ -15,6 +15,15 @@
 
 @SuppressWarnings("javadoc")
 public class TestStAXReader2Writer extends AbstractTestRoundTrip {
+	
+	// ******************************************************************************
+	// ******************************************************************************
+	// StAX is really ugly - it has broken namespace and comment handling
+	// As a result, some of these test cases fail
+	// testComplex - because StAX ignores a Comment content
+	// testNamespaces - because StAX Can't handle redeclaring default Namespace to ""
+	// ******************************************************************************
+	// ******************************************************************************
 
 	@Override
 	Document prepare(Document doc) {

test/src/java/org/jdom2/test/cases/output/TestStAXStreamOutputter.java

@@ -55,6 +55,13 @@
 @SuppressWarnings("javadoc")
 public final class TestStAXStreamOutputter extends AbstractTestOutputter {
 
+	// ******************************************************************************
+	// ******************************************************************************
+	// StAX is really ugly - it breaks SurrogatePair handling with non-UTF8 encoding
+	// As a result, some of these test cases fail in Recent Java versions
+	// - most test*Surrogate*Pair tests.
+	// ******************************************************************************
+	// ******************************************************************************
 
 	private static final XMLOutputFactory soutfactory = XMLOutputFactory.newInstance();
 	private static final XMLInputFactory sinfactory = XMLInputFactory.newInstance();