Stronger Tridion field validation using Regular Expressions and XSD

Validation of content in SDL Tridion can be accomplished using the UI, but some input just can’t be validated with the default options in the Tridion UI. This article explains how you can improve content validation using Regular Expressions!

The SDL Tridion CMS stores content in XML. These XML’s are structured using XML Schema’s (XSD) which can be constructed using the Tridion UI. The Tridion UI allows developers to create structured content blocks (or components) including;

• Literal content
• Rich text
• Date/Time
• Complex type (e.g. embeddable schema)

Example of a Tridion Schema

The default input validation, however, is limited to default values and required fields. Using the power of regular expressions we can force our disobidiant users to enter text according to some constraints!

I’ll explain a regular expression validation using the example of a time only field. To start, switch to “Source” tab to view the underlying XSD Tridion generates for us. A typical XSD generated by Tridion is shown below;

<xsd:schema targetNamespace="uuid:1FBE4459-87D3-465A-B98E-E7A9F77D7FF9" ...>
 <xsd:annotation>
  <xsd:appinfo>
   <tcm:Labels>
    <tcm:Label ElementName="time" Metadata="false">time</tcm:Label>
   </tcm:Labels>
  </xsd:appinfo>
 </xsd:annotation>
 <xsd:import namespace="http://www.tridion.com/ContentManager/5.0/Instance"/>
 <xsd:element name="Content">
  <xsd:complexType>
   <xsd:sequence>
    <xsd:element name="time" minOccurs="0" maxOccurs="1" type="xsd:normalizedString"/>
   </xsd:sequence>
  </xsd:complexType>
 </xsd:element>
</xsd:schema>

This example schema contains only one field name “time” which is a XSD normalizedString. To add the Regular expression check modify the red line schema as follows:

<xsd:element name="To" minOccurs="1" maxOccurs="1">
 <xsd:simpleType>
  <xsd:restriction base="xsd:normalizedString">
   <xsd:pattern value="\d{2}:\d{2}"/>
  </xsd:restriction>
 </xsd:simpleType>
</xsd:element>

Note that the type attribute is removed from the element tag.

For those who have not master the Vulcan Mind Melting technique of writing regular expression; the regular expression \d{2}:\d{2} means input should contain two digits (\d{2}) followed by a colon (:) which is followed by another two digits (\d{2}). More info about regular expression can be found at regular-expressions.info.

Now when a user enters an invalid value according to your regular expression, the user is presented by an error message:

Tridion Regular Expression Error

Which is hardly any use to your users; but hey your just a developer :). But, seriously: use with care, your users will hate you for it!

Tags: SDL Tridion

This entry was posted on Wednesday, March 11th, 2009 at 11:04 and is filed under tridion. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.