The required field validator in Struts can be used to check if field is non-null. It can be used in either of the following forms:

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

One example usage of this validator is to validate a field whose value is pulled from a dropdown list which may contain no items (the items are generated dynamically).

Usage:

• Field-validator syntax:
  

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

   
• Plain-validator syntax:
  

  <validator type="required">
  		<param name="fieldName">myField</param>
  		<message>validation error message</message>
  </validator>

   

Parameters:

Struts Required Field Validator XML Examples:

• Field-validator example:
  

  <field name="myJob">
  	<field-validator type="required">
  		<message>You must specify your job.</message>
  	</field-validator>
  </field>

   
• Plain-validator example:
  

  <validator type="required">
  	<param name="fieldName">myJob</param>
  	<message>Please specify your current job.</message>
  </validator> 

2. Struts @RequiredFieldValidator Annotation

Usage: Put the @RequiredFieldValidatorannotation before the setter method or action method (in case of using plain-validator) in the following form:

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

Parameters:

Struts @RequiredFieldValidator Examples:

• Basic field-validator:
  

  @RequiredFieldValidator(message = "Please specify your current job.")
  public void setMyJob(String myJob) {
  	this.myJob = myJob;
  }

   
• Specifying i18n key for the message:
  

  @RequiredFieldValidator(message = "Default message", key = "form.validation.job")
  public void setMyJob(String myJob) {
  	this.myJob = myJob;
  }

   
• Plain-validator (annotating the action method):
  

  @RequiredFieldValidator(type = ValidatorType.SIMPLE,
  	message = "Please specify your current job.",
  	fieldName = "myJob")
  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 URL 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