Minor,  calling the setWriter() method to set the writer,
rather than explicitly setting the field:
  m_writer=writer;

Its just the wright thing to do.
diff --git a/src/org/apache/xml/serializer/ToXMLStream.java b/src/org/apache/xml/serializer/ToXMLStream.java
index 8086901..dcb895d 100644
--- a/src/org/apache/xml/serializer/ToXMLStream.java
+++ b/src/org/apache/xml/serializer/ToXMLStream.java
@@ -77,7 +77,7 @@
     public void CopyFrom(ToXMLStream xmlListener)
     {
 
-        m_writer = xmlListener.m_writer;
+        setWriter(xmlListener.m_writer);
 
 
         // m_outputStream = xmlListener.m_outputStream;