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:

Parameter name	Description
fieldName	Name of the field to validate. Required if using plain validator syntax.
regex	The regular expression which should be enclosed in a CDATA element.
caseSensitive	A boolean value specifies whether the expression should be matched against in a case-sensitive way. Default is true.
trim	A boolean value specifies whether the expression should be trimmed before matching. Default is true.
regexExpression	Defines the regular expression as an OGNL expression. This will be evaluated to String.
caseSensitiveExpression	Defines the caseSensitive parameter as an OGNL expression. This will be evaluated to boolean.
trimExpression	Defines the trim parameter as an OGNL expression. This will be evaluated to boolean.

 

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:

Parameter name	Required	Default value	Description
message	Yes		validation error message.
key	No		i18n key for validation error message.
messageParams	No		Additional parameters to customize the message.
fieldName	No		Specifies field name in case this validator type is plain-validator.
shortCircuit	No	false	Whether this validator is short circuit.
type	No	ValidatorType.FIELD	type of the validator: field-validator (FIELD) or plain-validator (SIMPLE).
regex	Yes		The regular expression.

 

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