How to Iterate Over Unknown Columns in XSLT

Question

Hi ....

The Title pretty much says it all. I have an XML document that I am processing with XSLT .... but I don't know how many columns (fields) that are in the XML document (therefore, obviously, I don't know their names). How can I determine the number of "unknown" fields there are? Also, how can I read the attributes, if any, for the unknown fields?

Example data ....

<Dataset>
   <Row>
       <UnknownCol1 Msg="HowDoIGetThisMsgAttribute?"/>
       <UnknownCol2 />
       <UnknownCol3 />
   </Row>
</Dataset>

Answer 1

There's easy ways around this problem.

For the example you provided you could use the following XPath:

select='/Dataset/Row/*/@Msg'

If you wanted a more specific example of this, you may want to make your question clearer on exactly what you'd like to do with the data and the unknown columns. Are you copying it exactly? What specifically do you want to transform it into? Do you have any keys you'd like to match?

That kind of thing.

Answer 2

How can I determine the number of "unknown" fields there are?

This XPath expression:

count(/*/*/*)

evalutes to the count of the elements, that a re children of the elements that are children of the top node of the XML document -- exactly what is wanted in this case.

If the "Row" element can have children whose name does not start with "UnknownCol",

then this XPath expression provides the count of elements, whose name starts with "UnknownCol", and that are children of elements that are children of the top element:

count(/*/*/*[starts-with(name(), "UnknownCol")])

In case the top element may have other children than "Row", then an XPath expression giving the required count is:

count(/*/Row/*[starts-with(name(), "UnknownCol")])

Also, how can I read the attributes, if any, for the unknown fields?

By knowing XPath :)

/*/Row/*[starts-with(name(), "UnknownCol")]/@*

selects all the attributes of all "UnknownCol"{String} elements

This XPath expression gives us the number of these attributes:

  count(/*/Row/*[starts-with(name(), "UnknownCol")]/@*)

This Xpath expression gives us the name of the k-th such attribute ($ind must be set to the number k):

name( (/*/Row/*[starts-with(name(), "UnknownCol")]/@*)[$ind] )

And finally, this XPath expression produces the value of the k-th such attribute:

string( (/*/Row/*[starts-with(name(), "UnknownCol")]/@*)[$ind] )

Edit: The OP commented that he completely doesn't lnow the names of the children element.

The fix is easy: simply remove the predicate from all expressions:

count(/*/*/*)

count(/*/Row/*)


/*/Row/*/@*


count(/*/Row/*/@*)

name( (/*/Row/*/@*)[$ind] )

string( (/*/Row/*/@*)[$ind] )

Answer 3

Here is a small sample of XSLT 1.0 code that transforms your input into a HTML table.

<xsl:template match="Dataset">
  <table>
    <thead>
      <tr>
        <xsl:apply-templates select="Row[1]/*" mode="th" />
      </tr>
    </thead>
    <tbody>
      <xsl:apply-templates select="Row" />
    </tbody>
  </table>
</xsl:template>

<xsl:template match="Row">
  <tr>
    <xsl:apply-templates select="*" mode="td" />
  </tr>
</xsl:template>

<xsl:template match="Row/*" mode="th">
  <th>
    <xsl:value-of select="local-name()" />
  </th>
</xsl:template>

<xsl:template match="Row/*" mode="td">
  <td>
    <xsl:value-of select="@Msg" />
  </td>
</xsl:template>

When applied to this sample input:

<Dataset>
  <Row>
    <UnknownCol1 Msg="Data_1_1" />
    <UnknownCol2 Msg="Data_1_2" />
    <UnknownCol3 Msg="Data_1_3" />
  </Row>
  <Row>
    <UnknownCol1 />
    <UnknownCol2 Msg="Data_2_2" />
    <UnknownCol3 Msg="" />
  </Row>
</Dataset>

this output is returned:

<table>
  <thead>
    <tr>
      <th>UnknownCol1</th>
      <th>UnknownCol2</th>
      <th>UnknownCol3</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Data_1_1</td>
      <td>Data_1_2</td>
      <td>Data_1_3</td>
    </tr>
    <tr>
      <td></td>
      <td>Data_2_2</td>
      <td></td>
    </tr>
  </tbody>
</table>