Use USERID from DB and increment it using position() to create new USERID's?

Question

I'm trying to do the following in XSQL:
<?xml version="1.0"?>
<database connection="test" xmlns:xsql="urn:oracle-xsql">
<xsql:include-request-params/>
<xsql:query id-attribute="" tag-case="lower" rowset-element="maxuserid" row-element="idnum">
SELECT MAX(USER_ID) AS "USERID"
FROM LKUP_USER
</xsql:query>
<xsql:insert-request table="LKUP_USER" transform="/dvd/xsl/admin/createusertransform.xsl"/>
</database>and XSL:
<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/">
<ROWSET>
<xsl:choose>
<xsl:when test="/request/parameters[not(row)]">
<xsl:for-each select="/request/parameters">
<xsl:call-template name="generate-rows"/>
</xsl:for-each>
</xsl:when>
<xsl:otherwise>
<xsl:for-each select="/request/parameters/row">
<xsl:call-template name="generate-rows"/>
</xsl:for-each>
</xsl:otherwise>
</xsl:choose>
</ROWSET>
</xsl:template>
<xsl:template name="generate-rows">
<ROW>
<FIRSTNAME><xsl:value-of select="firstname"/></FIRSTNAME>
<LASTNAME><xsl:value-of select="lastname"/></LASTNAME>
<PASSWORD><xsl:value-of select="password"/></PASSWORD>
<EMAIL><xsl:value-of select="user-email"/></EMAIL>
<ACCESSLEVEL><xsl:value-of select="accesslvl"/></ACCESSLEVEL>
<USER_ID><xsl:value-of select="/maxuserid/idnum/userid + position()"/></USER_ID>
</ROW>
</xsl:template>
</xsl:stylesheet>which returns the following:
<?xml version="1.0" ?>
- <!-- <?xml-stylesheet type="text/xsl" href="/dvd/xsl/admin/createeditdeleteuserconfirm.xsl"?>
-->
- <database>
- <request>
- <parameters>
<password>test</password>
<lastname>test</lastname>
<firstname>test</firstname>
<accesslvl>5</accesslvl>
<user-email>test</user-email>
</parameters>
- <session>
<access>1</access>
<emailparam>[email protected]</emailparam>
<adminfirstname>Malik</adminfirstname>
<adminlastname>Graves-Pryor</adminlastname>
</session>
- <cookies>
<JServSessionIdroot>57ta3u4mns</JServSessionIdroot>
</cookies>
</request>
- <maxuserid>
- <idnum>
<userid>17</userid>
</idnum>
</maxuserid>
- <xsql-error action="xsql:insert-request">
<message>'java.sql.SQLException: ORA-01722: invalid number ' encountered during processing ROW element 1. All prior XML row changes were rolled back. in the XML document.</message>
</xsql-error>
</database>You can see what I'm trying to do, but I can't figure out exactly how to implement it. I want to avoid the problem of conflicting USER_ID values in the Oracle DB, so I figured, pull out the max USER_ID before submission and use that when 'row-ifying' the data to create new USER_ID which are incremented based on the position() function.
Help? Is this even possible?
p.s.: I realize that I might not be able to do this because the query is not a "request". Is there another way of accomplishing this task?
p.p.s.: I don't have my XSLT book yet..
Malik Graves-Pryor

Answer 1

My book, Building Oracle XML Applications, has lots of XSLT material and examples :-)
You should use:
<xsql:set-stylesheet-param>
to accomplish this. Remember again that the XML that the <xsql:insert-request> sees is not the XML of your data page, but the POSTED XML. The posted XML document will not have the maxid value in it. So, instead just use a top-level stylesheet parameter in your stylesheet:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<!-- Top level stylesheet parameter -->
<xsl:param name="maxid"/>
<xsl:template match="/">
Rest of template here.
Refer to value of maxid in any XPath expression
in the stylesheet with $maxid
</xsl:stylesheet>then in your XSQL page, you use <xsql:set-stylesheet-param> instead of <xsql:query> like this:
<xsql:set-stylesheet-param name="maxid">
select max(user_id) from lkup_user
</xsl:set-stylesheet-param>However -- and this is not an XSQL issue, but a general database thing -- you need to be careful about concurrency issues using the SELECT MAX() trick. If two requests come in simultaneously, they will both SELECT MAX() and get the same current maximum number, then both try to insert a new user. One will (presumably) violate your primary key constraint.
It's better to use database SEQUENCES instead, so the numbers are guaranteed to be unique. To use a sequence you would just change your SQL statement above to be:
SELECT yoursequencename.NEXTVAL FROM DUAL
instead of the SELECT MAX() query.