|Apache Struts 2 Documentation > Home > FAQs > Cookbook > How to validate field formats, such as a phone number|
Validating the format of String fields for patterns (such as a phone number) is easy with StringRegexValidator (named "regex" in the default validator configuration).
Simply add the validator the field in question, and supply a regular expression to match it against.
<validators> <field name="phone"> <field-validator type="regex"> <param name="expression">\([\d][\d][\d]\) [\d][\d][\d]-[\d][\d][\d][\d]</param> <message>Phone number must be in the format (XXX) XXX-XXXX</message> </field-validator> </field> </validators>
If your expression tests against alpha characters, you may be interested in the "caseSensitive" parameter of with Validator as well. It defaults to "true".