Web service that streams a clob to the calling application

Question

I need to produce a web service that streams a clob to a calling application: what I have currently is a web service that contains calls to htp, thinking this would serve as a way for a user to download a clob from the procedure that the web service is based on (see Trouble calling htp in a web service procedure
I can't get that approach to work at all, so rather than repeatedly bang my head against the wall I'll raise the following question: is there a standard approach whereby a clob can be streamed to the application consuming the web service? Note that I have limited myself in that I'm consuming the WS using APEX - APEX would like to store a returned value from a FUNCTION web service in a page item or a collection, but I will need to be returning very large CLOBs at times, so this is not an option.
I'm sure there must be examples of web services being used to return large streams of data returned by stored procedures but I can't seem to find them Could anyone point me in the right direction?

Answer 1

Ok, I've had to change tack. I've now recreated the web service and have handled the large CLOB as a streaming attachment: this performs well when running the test in Enterprise Manager as it returns a big CLOB very quickly. My problem is consuming this big SOAP message. I have tried calling this web service from a PLSQL procedure shown below but I get the following error:
ORA-29541: class XMLDBMASTER.oracle/jpub/runtime/dbws/DbwsProxy could not be resolved
When testing the WS there is obviously a automatically generated stub that will handle the returned SOAP message and it's streaming attachment. How is calling this from a DB procedure different, must I supply a proxy to the procedure manually?
Please, if anyone has any clue could they give me a shout? (Procedure below)
PROCEDURE run_ws (p_resid IN VARCHAR2,p_filename VARCHAR2, p_filter_str IN VARCHAR2)
AS
l_service UTL_DBWS.service;
l_call UTL_DBWS.call;
l_result ANYDATA;
l_wsdl_url VARCHAR2(1024);
l_service_name VARCHAR2(200);
l_operation_name VARCHAR2(200);
l_input_params UTL_DBWS.anydata_list;
v_mime VARCHAR2 (48) := NULL;
v_length NUMBER;
v_clob CLOB;
v_file_name VARCHAR2 (2000);
v_buf VARCHAR2 (32000);
v_amt NUMBER := 4000;
v_pos NUMBER := 1;
BEGIN
l_wsdl_url := 'http://ltp003357.sepanet.sepa.org.uk:8888/getXMLclob/getXMLclob';
l_service_name := 'getXMLclob';
l_operation_name := 'getClob';
l_service := UTL_DBWS.create_service (
wsdl_document_location => URIFACTORY.getURI(l_wsdl_url),
service_name => l_service_name);
l_call := UTL_DBWS.create_call (
service_handle => l_service,
port_name => NULL,
operation_name => l_operation_name);
l_input_params(1) := ANYDATA.ConvertVarchar2(p_resid);
l_input_params(2) := ANYDATA.ConvertVarchar2(p_filename);
l_input_params(3) := ANYDATA.ConvertVarchar2(p_filter_str);
l_result := UTL_DBWS.invoke (
call_handle => l_call,
input_params => l_input_params);
UTL_DBWS.release_call (call_handle => l_call);
UTL_DBWS.release_service (service_handle => l_service);
v_clob:=ANYDATA.AccessClob(l_result);
OWA_UTIL.mime_header ('text/xml', FALSE);
HTP.p ('Content-length: ' || v_length);
HTP.p ('Content-Disposition: attachment; filename="' || NVL('user_test','user_query.xml') || '"');
OWA_UTIL.http_header_close;
BEGIN
v_pos := 1;
LOOP
DBMS_LOB.READ (v_clob
, v_amt
, v_pos
, v_buf
v_pos := v_pos + v_amt;
HTP.prn (v_buf);
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
NULL;
END;
END run_ws;