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Working with Expressions, Variables and xsl:for-each in XSLT
This is the fourth article in a series focusing on developing XSLT-oriented applications using ASP.NET 2.0. Even though the series is based on ASP.NET 2.0, I use it only as a transformation engine. The entire focus is on working with XSLT. You can use any transformation engine according to your requirements (such as Java or others).
In this article, I will focus on working with expressions, defining, initializing and using variables and finally the “xsl:for-each” construct available in XSLT. The entire setup and sample XML for this article is the same as that of the first two articles in this series. If you come across any problems, I strongly suggest that you go through my first and second articles in this series.
The entire solution (source code) for this article is available as a free download (in the form of a zip). All the applications in this series have been developed using Microsoft Visual Studio 2005 Professional Edition on Microsoft Windows Server 2003 Standard Edition together with Microsoft SQL Server 2005 Developer Edition as the database. You can even directly copy and paste the code given in this article and save it with the extensions XML or XSL to work with your own XSL parsers/engines.
I didn’t really test any of the code in any of the other tools/IDEs/servers/editions/versions. If you have any problems, please feel free to post in the discussion area.
Working with simple expressions in XSLT
Let us start with a business need such that I would like to have all the employee details listed with:
salary (which is listed by the monthly rate)
annual salary (salary multiplied by 12)
I would like to implement the above business need using an “expression” within “xsl:value-of.” The following is the entire code for the same:
<?xmlversion="1.0"encoding="utf-8"?>
<xsl:stylesheetversion="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:templatematch="/">
<tableborder="1">
<xsl:apply-templatesselect="SQLData/Rows" />
</table>
</xsl:template>
<xsl:templatematch="SQLData/Rows">
<tr>
<td>
<xsl:value-ofselect="Empno"/>
</td>
<td>
<xsl:value-ofselect="Ename"/>
</td>
<xsl:apply-templatesselect="Sal" />
<td>
<xsl:value-ofselect="Deptno"/>
</td>
</tr>
</xsl:template>
<xsl:templatematch="Sal">
<td>
<xsl:value-ofselect="text()"/>
</td>
<td>
<xsl:value-ofselect="text() * 12"/>
</td>
</xsl:template>
</xsl:stylesheet>
When the above code gets executed, you are likely to get the following transformation:
<tableborder="1">
<tr>
<td>1001</td>
<td>Jag</td>
<td>4400</td>
<td>52800</td>
<td>10</td>
</tr>
<tr>
<td>1002</td>
<td>Chat</td>
<td>2800</td>
<td>33600</td>
<td>20</td>
</tr>
.
.
.
</table>
The most important statement within the above code is the following:
<xsl:value-ofselect="text() * 12"/>
The above statement simply gets the text (or content) associated with the current context and multiplies it by 12 (which gives us the annual salary).
In the previous section, we were able to display all the employee details along with their salaries and annual salaries. We calculated annual salaries using expressions within “xsl:value-of.”
Now, we shall achieve the same using variables in XSLT. The following is the entire code rewritten for this purpose:
<?xmlversion="1.0"encoding="utf-8"?>
<xsl:stylesheetversion="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:templatematch="/">
<tableborder="1">
<xsl:apply-templatesselect="SQLData/Rows" />
</table>
</xsl:template>
<xsl:templatematch="SQLData/Rows">
<tr>
<td>
<xsl:value-ofselect="Empno"/>
</td>
<td>
<xsl:value-ofselect="Ename"/>
</td>
<xsl:apply-templatesselect="Sal" />
<td>
<xsl:value-ofselect="Deptno"/>
</td>
</tr>
</xsl:template>
<xsl:templatematch="Sal">
<td>
<xsl:value-ofselect="text()"/>
</td>
<xsl:variablename="AnnSal"select="text()"/>
<td>
<xsl:value-ofselect="$AnnSal * 12"/>
</td>
</xsl:template>
</xsl:stylesheet>
The output of the above code would be the same as that of the previous section.
Coming to the explanation of the above code, every variable in XSLT must be declared using the “xsl:variable.” The value can be directly assigned using the “select” attribute or in the form of content.
To use variables at other parts of the same XSLT, just specify the name of the variable and precede it with the symbol “$”.
The most important construct from the above XSLT is the following:
<xsl:for-eachselect="SQLData/Rows">
.
.
</xsl:for-each>
The above construct automatically iterates for every presence of “SQLData/Rows.” The execution of that construct gets completed only if no more “SQLData/Rows” are available for processing. We can even nest “xsl:for-each” constructs according to our requirements.
Let us consider a business need which requires the display of all employee details along with employee salaries and grades. The grade of the employee is based on the salary. If the salary is above 3000, the employee belongs to the "high" grade; otherwise, he or she belongs to the "low" grade.
I would like to satisfy the above business need by using “for,” “choose” and a separate “template.” The following is the code to accomplish this task:
When we generate tables from the existing XML data, there may be a need to generate serial numbers in the first column of every row fetched by “xsl:for-each.”
The following is a simple solution to deal with this issue:
Let us consider a business need which requires the display of all employee details along with highlighting the salary in red, if the salary is more than 3000. I would like to fulfill this business need by using “for” and “choose.”
From the above code, you can observe that I used “xsl:choose,” “xsl:when” and “xsl:otherwise” within “xsl:for-each.”
I hope you enjoyed the article and any comments, suggestions, feedback, bugs, errors, enhancements etc. are highly appreciated at http://jagchat.spaces.live.com
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