Question
Answer and Explanation
Checking for blank values in XSLT can be achieved using a few different techniques, depending on what you consider "blank". In XSLT, a blank value usually refers to an empty string, a string containing only whitespace, or a missing node.
Here are several methods you can use:
1. Checking for Empty Strings using the `string()` function:
- The `string()` function returns the string value of a node. You can check if this string is empty by comparing it to an empty string.
Example:
<xsl:if test="string(someNode) = ''">
<!-- The node 'someNode' is either missing or has an empty string value. -->
</xsl:if>
2. Checking for Missing Nodes using a direct test:
- You can directly test if a node exists. If a node is missing, it will evaluate to false in an XSLT test.
Example:
<xsl:if test="not(someNode)">
<!-- The node 'someNode' is missing or has an empty value -->
</xsl:if>
3. Checking for Whitespace-only Strings using `normalize-space()` Function:
- To handle strings that contain only spaces, tabs, and line breaks, you can use `normalize-space()`. This function removes leading and trailing whitespace and reduces internal sequences of whitespace to a single space character. If the result is an empty string, the original string was either empty or contained only whitespace.
Example:
<xsl:if test="normalize-space(someNode) = ''">
<!-- The node 'someNode' has an empty value or only contains whitespace. -->
</xsl:if>
4. Combining Checks for Robust Blank Value Detection:
- You can combine these checks using the `or` operator to test for all possible forms of blank values:
Example:
<xsl:if test="not(someNode) or string(someNode) = '' or normalize-space(someNode) = ''">
<!-- The node 'someNode' is missing, empty or has only whitespace-->
</xsl:if>
Remember to adjust the specific test based on what you consider as "blank" in your data set. Use the `not()` function, the `string()` function with comparison, or the `normalize-space()` function according to what works best for your particular scenario in XSLT.