Oracle XML classgenerator /Servlet problem

Question

Hi,
I'm developing a servlet that accepts an HTTP request, contacts a database, processes the request and return an XML document back to the browser. The XML document returned is dependent on which selection a user makes.
The problem is that on first request, say user selects "choice one", the correct XML document is returned. However, when the browser's back button is used to go back and make the same choice as previous(ie "choice one"), Explorer 4.5 displays an empty page while netscape 4.5 return a document contains no data error.
I used oracle xmlclassgenerator to generate the classes that create the XML document to be returned. The problem certainly lies in the method of my servlet that uses these classes to generate the XML document because when I replace the whole method with println statement every thing works fine(but of course without the XML document).
The content of the method is as follows.
ACCOUNT acc = new ACCOUNT(id);
//Create a child and add child to root node
NUM_OF_RESIDENTS nr = new NUM_OF_RESIDENTS(num);
acc.addNode(nr);
//Create another child and add to root node
FIXED_COST fc = new FIXED_COST();
ELECTRICITY el = new ELECTRICITY(elec);
GAS g = new GAS(gas);
WASH_MACHINE wm = new WASH_MACHINE(wash);
WATER wat = new WATER(water);
OTHER oth = new OTHER(other);
fc.addNode(el);
fc.addNode(g);
fc.addNode(wm);
fc.addNode(wat);
fc.addNode(oth);
//finally add to root node
acc.addNode(fc);
//Create another child
TELEPHONE tl = new TELEPHONE();
SUBSCRIPTION sub = new SUBSCRIPTION(tel);
COST_PER_TICK cpt = new COST_PER_TICK(tick);
tl.addNode(sub);
tl.addNode(cpt);
acc.addNode(tl);
//Create another child
// PREVIOUS_ACCOUNT pacc = new PREVIOUS_ACCOUNT();
for(int i=0; i<previous_details.size(); i++){
//Create another child
PREVIOUS_ACCOUNT pacc = new PREVIOUS_ACCOUNT();
PreviousDetails pd = (PreviousDetails)previous_details.elementAt(i);
String name = pd.getName();
String credit = pd.getCredit();
String debit = pd.getDebit();
NAME n = new NAME(name);
LAST_CREDIT lc = new LAST_CREDIT(credit);
LAST_DEBIT ld = new LAST_DEBIT(debit);
pacc.addNode(n);
pacc.addNode(lc);
pacc.addNode(ld);
acc.addNode(pacc);
for(int i=0; i<acc_dates.size(); i++){
String str = (String)acc_dates.elementAt(i);
ACCOUNT_DATE ad = new ACCOUNT_DATE(str);
acc.addNode(ad);
acc.validateContent();
ByteArrayOutputStream out1 = new ByteArrayOutputStream(1024);
acc.print(out1);
res.setContentType("text/plain");
ServletOutputStream os = res.getOutputStream();
PrintWriter out = new PrintWriter(os);
out.println(out1.toString());
out.close();
catch(Exception e){}
Am I doing somthing wrong here?
Thanks.
null

Answer 1

Hi,
I had a very similar problem, which turned out to be the way that I was referencing one schema from another. Originally I had something like the following in my main XSD:
<xs:import namespace="http://www.govtalk.gov.uk/people/bs7666" schemaLocation="bs7666-v2-0.xsd"/>When I tried to register the schema using the schemaURL of 'http://www.govtalk.gov.uk/people/bs7666/bs7666-v2-0.xsd' I got ORA-31000: Resource 'bs7666-v2-0.xsd' is not an XDB schema document. I then tried to registering the schema using just it's name ie schemaURL => 'bs7666-v2-0.xsd' and this worked!
With further investigation I found that if I change the schemaLocation in the import to a full URL I could then register the schema using that same URL:
Reference from my main schema
<xs:import namespace="http://www.govtalk.gov.uk/people/bs7666"
      schemaLocation="http://www.govtalk.gov.uk/people/bs7666/bs7666-v2-0.xsd"/>
BEGIN
   DBMS_XMLSCHEMA.registerSchema
     ( SCHEMAURL => 'http://www.govtalk.gov.uk/people/bs7666/bs7666-v2-0.xsd'
     , SCHEMADOC => bfilename('XMLDIR','bs7666-v2-0.xsd')
     , LOCAL => FALSE
END;Maybe someone could shed some light on the best practice for registering schemas? I understand that schemaURL is really just a reference for the schema and not actually used to locate the schema but is it better to use full URLs?
Regards,
Tom