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Working with Both xsl:if and xsl:choose in XSLT
This is the third 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 will be 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 the "xsl:choose" and "xsl:if" constructs 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 you to 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 with the XML or XSL extensions and work with your own XSL parsers/engines.
I didn't really test any of the code in any of the tools/IDEs/servers/editions/versions. If you have any problems, please feel free to post in the discussion area.
Working with "xsl:if" in XSLT
I already introduced "xsl:choose" in my previous article. Now, I will start discussing "xsl:if."
Let us start with a business need. Say that I would like to have all the employee details listed with:
salary in red, if earnings are more than 4000
salary in blue, if earnings are more than 3000 and less than 4000
I would like to implement the above business need using the "xsl:if" construct in XSLT. 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">
<xsl:iftest="text() > '4000'">
<tdstyle="color: red">
<xsl:value-ofselect="."/>
</td>
</xsl:if>
<xsl:iftest="text() > '3000' and text() < '4000'">
<tdstyle="color: blue">
<xsl:value-ofselect="."/>
</td>
</xsl:if>
<xsl:iftest="text() > '0' and text() < '3000'">
<td>
<xsl:value-ofselect="."/>
</td>
</xsl:if>
</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>
<tdstyle="color: red">4400</td>
<td>10</td>
</tr>
<tr>
<td>1002</td>
<td>Chat</td>
<td>2800</td>
<td>20</td>
</tr>
<tr>
<td>1003</td>
<td>Winner</td>
<tdstyle="color: blue">3700</td>
<td>10</td>
</tr>
<tr>
<td>1004</td>
<td>Dhan</td>
<tdstyle="color: red">5000</td>
<td>20</td>
</tr>
</table>
The most important problem with "xsl:if" is that it doesn't have (at the time of this writing) any "else" structure. If you need an "else" structure, you may have to use "xsl:choose" as explained in my previous article.
In the previous section, I already introduced "xsl:if." And now, I want to nest "xsl:if" within another and make things a bit complicated. To do that, we may have to modify our business need.
Let us modify our business need in such a way that I would like to have all the employee details listed with:
salary in red, if earnings are more than 4000
salary in blue, if earnings are more than 3000 and less than 4000
salary must not be shown for the employees working in department 10
The entire XSLT code for the above business need is as follows:
That tests whether the next sibling node named "Deptno" does or does not equal 10. If you are new to this, I suggest you to refer my second article in this series.
As you are familiar with both "xsl:if" and "xsl:choose" by now, let us nest them together. If you are new to "xsl:choose," I suggest you go through my second article in this series.
Let us modify our business need in such a way that I would like to have all the employee details listed with:
salary in red, if earnings are more than 2500 and less than 4000
salary must not be shown for the employees working in department 10
The entire XSLT code for the above business need is as follows:
Up until now, we have seen several types of combinations using "xsl:if" and "xsl:choose." Now, we shall embed "xsl:choose" within another "xsl:choose."
In this case, I simply want to work with the same business need given in the previous section. The entire modified XSLT code for the same business need is as follows:
<?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">
<xsl:choose>
<xsl:whentest="text() > '2500' and text() < '4000'">
In all of the previous examples, we worked with several conditions based on the data. But "xsl:if" is not meant only for conditions. It can also be used to test whether or not there exist any nodes/sub-nodes/leaves etc. under the current node.
For example, the following displays a message if the current "context" has any child elements named "dept no."
<xsl:if test="Deptno">
Got at least one Deptno as child element.
</xsl:if>
And not only that, you can also count the number of child elements using the following code fragment:
<xsl:if test="count(Deptno) = 1">
Got only one Deptno as child element
</xsl:if>
Similarly, if you wanted to work with attribute values rather than text, you can provide attribute names preceded with "@". The following code shows an example:
<xsl:if test="@Sal < '2000')">
Salary is less than 2000 is "1667".
</xsl:if>
In all the above cases, I simply mentioned "xsl:if." The same points apply to "xsl:choose."
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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