xstrm.read();

[jacek]

then I need put the content of strm between tag PLAIN. How this?

If xstrm contains text everything is OK --- < & > were just converted to entities, but if xstrm contains text and XML tags, then you can't use a text node to add it to the document.

Consider this fragment of XML document:

...
xxx
<tag>yyy</tag>
zzz
...

Here you have 4 nodes. Three text nodes ("xxx", "yyy" and "zzz") and element node "tag". You can't use a single node instead of 4 nodes.

Why do you need to read data from that file? Maybe you could create a DOM document and then just write it to a file?