Struts Conversion Validator Example

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:

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

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.