Calling rss feed with plsql - web-services

Question

I'm trying to call a webservice from plsql. I have the following code (which works):
CREATE OR REPLACE PROCEDURE WEBSERVICE AS
v_xml XMLTYPE;
BEGIN
v_xml := XMLTYPE(UTL_HTTP.REQUEST(URL => 'http://dev.markitondemand.com/Api/Quote?symbol=AAPL'));
FOR x IN (SELECT
EXTRACTVALUE(VALUE(p), '/Data/Status/text()') AS title
FROM TABLE(XMLSEQUENCE(EXTRACT(v_xml, '/QuoteApiModel/Data'))) p)
LOOP
DBMS_OUTPUT.PUT_LINE(x.title);
END LOOP;
COMMIT;
END;
But this code does not work:
CREATE OR REPLACE PROCEDURE WEBSERVICE AS
v_xml XMLTYPE;
BEGIN
v_xml := XMLTYPE(UTL_HTTP.REQUEST(URL => 'http://xkcd.com/rss.xml'));
FOR x IN (SELECT
EXTRACTVALUE(VALUE(p), 'item/title/text()') AS title
FROM TABLE(XMLSEQUENCE(EXTRACT(v_xml, '/rss/channel/item'))) p)
LOOP
DBMS_OUTPUT.PUT_LINE(x.title);
END LOOP;
COMMIT;
END;
It gives me the following error:
Connecting to the database oracle.
ORA-31011: XML parsing failed
ORA-19202: Error occurred in XML processing
LPX-00007: unexpected end-of-file encountered
ORA-06512: at "SYS.XMLTYPE", line 310
ORA-06512: at "SYS.WEBSERVICE", line 4
ORA-06512: at line 2
Process exited.
Disconnecting from the database oracle.
The difference I noticed is that the xkcd rss feed has an xml header and the other one doesn't. What should I do to make this work?

Answer 1

You right, error occured because of presence of XML header.
Workaround is to use XMLParse(document ...) to parse XML:
select xmlparse(document UTL_HTTP.REQUEST(URL => 'http://xkcd.com/rss.xml'))
into v_xml
from dual;
Example SQLFiddle with results from xkcd.com.
Notice, that according to documentation HTTP_UTIL.Request function returns only first 2000 bytes of server response, so you can get incomplete XML with such request.
Update
More elegant way to extract values from XML is to use XMLTable() function with XQuery :
FOR x IN (
select title
from
XMLTable(
'for $i in $p/rss/channel/item/title return $i'
passing
XMLParse(document UTL_HTTP.REQUEST(URL => '...')) as "p"
columns
title varchar2(4000) path '//title'
)
)
LOOP
DBMS_OUTPUT.PUT_LINE(x.title);
END LOOP;
SQLFiddle
At least, this method allows you to create more flexible options for different sources of RSS.