Jakarta Struts Cookbook

8.3. Validating Dependent Fields in Struts 1.1

Problem

You are using Struts 1.1 and you want to validate a field based on the value of another related field.

Solution

Use the requiredif validator. The field element, in this snippet from a validation.xml file, indicates that the zipCode field is required if the city or state field is null:

<!-- zipCode is required if city is null or state is null -->
<field property="zipCode" depends="requiredif">
    <arg key="prompt.zipCode"/>
    <var>
        <var-name>field[0]</var-name>
        <var-value>city</var-value>
    </var>
    <var>
        <var-name>fieldTest[0]</var-name>
        <var-value>NULL</var-value>
    </var>
    <var>
        <var-name>field[1]</var-name>
        <var-value>state</var-value>
    </var>
    <var>
        <var-name>fieldTest[1]</var-name>
        <var-value>NULL</var-value>
    </var>
    <var>
        <var-name>fieldJoin</var-name>
        <var-value>OR</var-value>
    </var>
</field>

Discussion

The Struts Validator has always worked well for single-field validations. Cross-field validation, that is validating two or more dependent fields, wasn't supported by the Validator until Struts 1.1. The requiredif validation rule was introduced at that time to address the problem. Interestingly enough, the requiredif rule lifespan will be short. It is being deprecated in Struts 1.2 and is being replaced by the validwhen rule, discussed in Recipe 8.4.

The validation shown in the Solution would be used on a form where you were retrieving a user's address. If users specify a zip code, then they can omit the city and state; these values would ...