The Struts validation framework provides the required string validator in order to check a String field is not null and not empty (“”). It comes with two flavors:

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

 

1. Struts Required String Validator XML

Usage:

• Field-validator syntax:
  

  <field name="fieldName">
  	<field-validator type="requiredstring">
  		<param name="param name">param value</param>
  		<message>validation error message</message>
  	</field-validator>
  </field>

   

• Plain-validator syntax:
  

  <validator type="requiredstring">
  		<param name="param name">param value</param>
  		<message>validation error message</message>
  </validator> 

 

Parameters:

Parameter name	Required	Default value	Description
fieldName			Required if using plain validator syntax
trim	No	true	A boolean value indicates whether to trim the field’s value before validating.
trimExpression	No		An OGNL expression used to trim the field’s value.

 

Struts Required String Validator XML Examples:

• Field-validator example:
  

  <field name="firstName">
  	<field-validator type="requiredstring">
  		<param name="trim">false</param>
  		<message>You must enter your first name</message>
  	</field-validator>
  </field>

   

• Plain-validator example:
  

  <validator type="requiredstring">
  	<param name="fieldName">firstName</param>
  	<param name="trim">false</param>
  	<message>You must enter your first name</message>
  </validator> 

 

2. Struts @RequiredStringValidator Annotation

Usage: Annotate setter method of the String field by:

@RequiredStringValidator(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).
trim	No	true	Whether to trim the field’s value before validating.

 

Struts @RequiredStringValidator Annotation Examples:

• Basic field-validator:
  

  @RequiredStringValidator(message = "Please enter your first name")
  public void setFirstName(String firstName) {
  	this.firstName = firstName;
  }

   

• Specifying i18n key for the message:
  

  @RequiredStringValidator(message = "Default message", key = "form.validation.firstName")
  public void setFirstName(String firstName) {
  	this.firstName = firstName;
  }

   

• Plain-validator (annotating the action method):
  

  @RequiredStringValidator(type = ValidatorType.SIMPLE, fieldName = "firstName",
  	message = "Please enter your first name")
  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 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