Jakarta Struts Cookbook

8.8. Validating Field Equality in Struts 1.2

Problem

You want to validate that two fields on a form have the same value, taking advantage of the new features provided by the Validator in Struts 1.2.

Solution

Use the validwhen rule with a test expression that checks if the validated field is equals the other field. In Example 8-12, the test expression specifies the password2 field (*this*) must equal the password field for the validation to pass.

Example 8-12. Validating field equality with validwhen

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE form-validation PUBLIC
          "-//Apache Software Foundation//DTD Commons Validator Rules 
          Configuration 
          "http://jakarta.apache.org/commons/dtds/validator_1_1_3.dtd">
<form-validation>
    <formset>
        <form name="RegistrationForm">
            <field property="emailAddress"
                    depends="required,email">
                <arg key="prompt.emailAddress"/>
            </field>
            <field property="password"
                    depends="required">
                <arg key="prompt.password"/>
            </field>
            <field property="password2"
                    depends="required,validwhen">                 
                <arg position="0" key="prompt.password2"/>
                <arg position="1" key="prompt.password"/>
                <msg name="validwhen" key="error.password.match"/>
                <var>
                    <var-name>test</var-name>
                    <var-value>(*this* == password)</var-value>
                </var>
            </field>
        </form>
    </formset>
</form-validation>

Discussion

If you compare this Solution with Recipe 8.7, you can see the same business rule is implemented without requiring a custom Validator rule. The validwhen rule used here accepts a test expression, which it evaluates. ...