Serialize DOM between two ejb's performance

Question

Hi,
I am working with XML in a ejb container and I used JDOM Document (org.jdom.Document) to send the xml document between two ejb's, I picked JDOM because the Document implements the Serilizable interface. Then I did some performance tests on sending JDOM between two ejb's. I also did tests on sending a String rep. of the XML between the same ejb's. The result supprised me very much.
Here is the testing code:
// init
dom.loadFromPath("C:\\booklist.xml");
String xml = dom.getXML();
org.jdom.Document doc = db.build(dom.queryDocument());
// ... ejb lookup etc...
// ejb test
long start2 = System.currentTimeMillis();
for ( int i = 0 ; i < 1000; i ++ )
test.jdomTest(doc); // jdom doccument
long end2 = System.currentTimeMillis();
// string test...
long start1 = System.currentTimeMillis();
for ( int i = 0 ; i < 1000; i ++ )
test.stringTest(xml); // String
long end1 = System.currentTimeMillis();
and the results:
JDOM: 41703 msek
String: 313 msek
Send String and load him into a DOM in the receiving ejb: 5266 msek.
I have always thought that working with xml on a string format would be to much overhead.
Could somebody clearify this for me? Does this test results make any sense?
- thanks, Lubbi Tik

Answer 1

The serialisation process works at the object level, so to serialise an object you must first serialise every attribute of that object. The specification for serialisation states that every object which wants to be serialisable must have attributes which are primative types (eg int, long etc etc) or attributes which are objects which are serialisable. So to serialise a JDOM you must serialise each of the child nodes in the document, it would be a lot of object manipulation in this example. To serialise a String however, is much easier as it is a much less complex type.
Cheers,
Peter.