The conversion validator is a Struts field validator that checks if a type conversion error occurs for a field. For example, if the user inputs the value “one” for an integer field, a conversion error will occur, and an error message will be displayed next to the field. This validator can be used in either of the following forms:

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

 

1. Struts Conversion Validator XML

 Usage:

• • Field-validator syntax:
    

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

     

  • Plain-validator syntax:
    

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

 

Parameters:

Parameter name	Description
fieldName	Name of the field to validate. Required if using plain validator syntax.

Struts Conversion Validator XML Examples:

• • Field-validator example:
    

    <field name="myAge">
    	<field-validator type="conversion">
    		<message>Please enter a number for your age!</message>
    	</field-validator>
    </field>

     

  • Plain-validator example:
    

    <validator type="conversion">
    	<param name="fieldName">myAge</param>
    	<message>Age must be a number!</message>
    </validator>

     

  • If you want to re-populate the user-entered value when the conversion error occurs, use the parameter repopulateFieldas follows:
    

    <field name="myAge">
    	<field-validator type="conversion">
    		<param name="repopulateField">true</param>
    		<message>Please enter a number for your age!</message>
    	</field-validator>
    </field> 

 

2. Struts @ConversionErrorFieldValidator Annotation

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

@ConversionErrorFieldValidator (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 @ConversionErrorFieldValidator Annotation Examples:

• • Basic field-validator (annotating field’s getter method):
    

    @ConversionErrorFieldValidator(
    	message = "Age must be a number (integer wanted!)"
    )
    public int getMyAge() {
    	return myAge;
    }

     

  • Specifying i18n key for the message (annotating field’s setter method):
    

    @ConversionErrorFieldValidator(
    	key = "form.validation.age",
    	message = "Age must be a number (integer wanted!)"	// default message
    )
    public void setMyAge(int myAge) {
    	this.myAge = myAge;
    }

     

  • Plain-validator (annotating the action method):
    

    @ConversionErrorFieldValidator(
    	type = ValidatorType.SIMPLE,
    	fieldName = "myAge",
    	message = "Age must be a number (integer wanted!)"
    ) 

 

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
• 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