Struts Regular Expression Validator Example

The Struts validation framework provides a built-in validator that is able to validate a field against a particular regular expression: the regular expression validator. That would be useful in cases we want to make sure the value entered by the user conforms to a specific pattern, e.g. phone number or zip code. We can use this validator in either of the following forms:

• XML: using type=”regex” attribute in <validator> or <field-validator> elements.
• Annotation: using @RegexFieldValidator annotation type to annotate getter/setter method of the field or action method (plain-validator).

1. Struts Regular Expression Validator XML

Usage:

• Field-validator syntax:

  <field name="fieldName">
  	<field-validator type="regex">
  		<param name="regex">regular expression</param>
  		<message>validation error message</message>		
  	</field-validator>
  </field>

   

• Plain-validator syntax:

  <validator type="regex">
  	<param name="fieldName">myField</param>
  	<param name="regex">regular expression</param>
  	<message>validation error message</message>
  </validator>

Parameters:

Struts Regular Expression Validator XML Examples:

In the following examples, we use the regular expression validator to validate a phone number field which can accepts only these characters: numbers (0-9), +, -, and *. Hence the following regular expression:

^\\+?[0-9\\-]+\\*?$

• Field-validator example:

  <field name="phoneNumber">
  	<field-validator type="regex">
  	    <param name="regex"><![CDATA[^\+?[0-9\-]+\*?$]]></param>
  	    <message>Please enter a valid phone number</message>
  	</field-validator>
  </field>

• Plain-validator example:

  <validator type="regex">
  	<param name="fieldName">phoneNumber</param>
  	<param name="regex"><![CDATA[^\+?[0-9\-]+\*?$]]></param>
  	<message>Please enter a valid phone number</message>
  </validator>

2. Struts @RegexFieldValidator Annotation

Usage: Put the @RegexFieldValidator annotation before the field’s setter/getter method or action method (in case of using plain-validator) in the following form:

@ReqexFieldValidator(param1 = "param 1 value", param2 = "param 2 value", ...)

Parameters:

Struts @RegexFieldValidator Annotation Examples:

• Basic field-validator (annotating setter method):

  @RegexFieldValidator(
  	regex = "^\\+?[0-9\\-]+\\*?$",
  	message = "Please enter a valid phone number"
  )
  public void setPhoneNumber(String phoneNumber) {
  	this.phoneNumber = phoneNumber;
  }

• Specifying i18n key for the message:

  @RegexFieldValidator(
  	regex = "^\\+?[0-9\\-]+\\*?$",
  	key = "form.validation.phoneNumber",
  	message = "This is the default message if the i18k key not found"
  )
  public void setPhoneNumber(String phoneNumber) {
  	this.phoneNumber = phoneNumber;
  }

• Plain-validator (annotating the action method):

  @RegexFieldValidator(
  	type = ValidatorType.SIMPLE,
  	fieldName = "phoneNumber",			
  	regex = "^\\+?[0-9\\-]+\\*?$",
  	message = "Please enter a valid phone number"
  )
  public String execute() {
  	return SUCCESS;
  }

Related Struts Form Validation Tutorials:

• Struts Form Handling Tutorial
• Struts Form Validation Tutorial
• Struts Date Range Field Validator Example
• Struts Integer Range Field Validator Example
• Struts String Length Field Validator Example
• Struts Required Field Validator Example
• Struts Expression Validator Example
• Struts URL Validator Example

Other Struts Tutorials:

• Introduction to Struts 2 framework
• Struts beginner tutorial (Eclipse + Tomcat + XML)
• Struts Beginner Tutorial with Annotations
• Struts beginner tutorial with Convention Plugin (zero-configuration)
• How to handle exceptions in Struts
• Send e-mail with attachments in Struts
• Struts File Upload Tutorial
• Struts - Spring - Hibernate Integration Tutorial

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.