如何参考给定的XSD在ORACLE 11g中生成XML？

Question

I am learning to generate XML in Oracle 11g PL/SQL language.

I would like to generate XML depending on the data I get from the db tables, but at same time it should follow the structure and validate the XML with reference to the XSD I am provided with.

I have registered the XSD schema through dbms_xmlschema.registerSchema and generated the XML through dbms_xmlquery.getXml using dynamic script and then validated it by using XMLTYPE.schemaValidate .

But in my process the flow is creating XML first and then validating it with XSD, so due to this I may not be able to get correct structure and need to work on structure while generating XML.

Is there any way I can generate the XML by referencing the XSD I stored so that I don't miss out on structure and the XML only gets created if the result of referencing is valid?

Answer 1

You can't really generate xml based on a schema. The best is probably to generate the xml into an xmltype variable and then validate this against the schema.

You can use the following plsql block (to be run as a script) as a starting point. Alter the query to use xml functions (XMLFOREST, XMLELEMENT, XMLATTRIBUTES) to generate the xmltype variable.

Once you have this inside l_xml you should be able to validate it against your schema. (Then I presume report the error if you need to or continue and process the xml as required)

My sample just pretty prints the xml and puts it in dbms output.

set serveroutput on;
declare
  l_error varchar2(4094);
  --
  l_xml xmltype;
  l_tmp varchar2(4096);  
begin
  dbms_output.put_line('Start');

  --generate variable from query
  select xmlelement("this:root"
      ,xmlattributes(
        'http://www.w3.org/2001/XMLSchema-instance' as "xmlns:xsi",
        'http://ic.ac.uk.relationshipvisualiser.app.data.InputData' as "xmlns:this"
      )
      ,xmlelement("this:subelement"
        ,'subelementValue'
      )
      ,xmlelement("this:subelement2"
        ,'subelementValue2'
      )
    )
  into l_xml
  from dual;  

  --todo Write code to validate l_xml against xsd schema

  --now output xml
  select XMLSERIALIZE(Document l_xml as CLOB INDENT SIZE = 2)
  into l_tmp
  from dual;
  dbms_output.put_line(l_tmp);


  dbms_output.put_line('End');
EXCEPTION WHEN OTHERS THEN
  l_error := NVL(SUBSTR(SQLERRM,0,990),'NULL');
  dbms_output.put_line(l_error || ':-' || NVL(SUBSTR(DBMS_UTILITY.FORMAT_ERROR_BACKTRACE,0,3000),'NULL')); 
end;