The URL validator in Struts can be used to check whether value of a String field is a valid URL or not. It can be used in either of the following forms:

• XML: using type=”url” attribute in <validator> or <field-validator> elements.
• Annotation: using @UrlValidator annotation type to annotate setter method of the field or action method.

NOTES: This validator does not treat empty value as invalid URL, thus it’s recommended to use this validator in conjunction with the required string validator if the field is also mandatory.

 

1. Struts URL Validator XML

Usage:

• Field-validator syntax:
  

  <field name="fieldName">
  	<field-validator type="url">
  		<message>validation error message</message>
  	</field-validator>
  </field>

   

• Plain-validator syntax:
  

  <validator type="url">
  		<param name="fieldName">myHomePage</param>
  		<message>validation error message</message>
  </validator>

   

Parameters:

Struts URL Validator XML Examples:

• Field-validator example:
  

  <field name="myHomePage">
  	<field-validator type="url">
  		<message>You must enter a valid URL</message>
  	</field-validator>
  </field>

   

• Plain-validator example:
  

  <validator type="url">
  	<param name="fieldName">myHomePage</param>
  	<message>Please specify a valid URL.</message>
  </validator> 

 

2. Struts @UrlValidator Annotation

Usage: Using the following annotation type before the setter method or action method (in case of using plain-validator):

@UrlValidator(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).

 

Struts @UrlValidator Annotation Examples:

• Basic field-validator:
  

  @UrlValidator(message = "Please enter a valid URL for your home page.")
  public void setMyHomePage(String myHomePage) {
  	this.myHomePage = myHomePage;
  }

   

• Specifying i18n key for the message:
  

  @UrlValidator(message = "Default message", key = "form.validation.homePage")
  public void setMyHomePage(String myHomePage) {
  	this.myHomePage = myHomePage;
  }

   

• Plain-validator (annotating the action method):
  

  @UrlValidator(type = ValidatorType.SIMPLE,
  	message = "Please enter a valid URL for your home page.",
  	fieldName = "myHomePage")
  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 Field Expression 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