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).

 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:

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:

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