now new entity is created in XML as well, not only as in-memory object

src/exception/DuplicateEntryException.java

@@ -0,0 +1,13 @@
+package exception;
+
+public class DuplicateEntryException extends EntityListIntegrityException {
+
+	public DuplicateEntryException() {
+		super();
+	}
+	
+	public DuplicateEntryException(String message) {
+		super(message);
+	}
+	
+}

src/exception/EntityListIntegrityException.java

@@ -0,0 +1,12 @@
+package exception;
+
+public class EntityListIntegrityException extends Exception {
+
+	public EntityListIntegrityException() {
+		super();
+	}
+
+	public EntityListIntegrityException(String message) {
+		super(message);
+	}
+}