Raible Designs

Struts Validator: Validating Two Fields Match

In the Struts Validator Guide, there is a section on how to create a pluggable validator that matches two fields. I've been using this server-side validator (as shown in the example) to do password/confirm password validation. This has worked great for me, but I've always wanted the Validator to have the client-side JavaScript method for it too. I wrote my own that just compared the two fields, but it's not the same as having one rendered for you (from validator-rules.xml). So yesterday, I did some tinkering and figured out how to add the JavaScript method to validator-rules.xml. So here's how to configure the whole thing (most of this is contained in the Validator Guide, save the JavaScript).

How To Add a TwoFields Validator

Step 1: Create a class with a validateTwoFields method. In my code, my class is ValidationUtil and has the following method:

public static boolean validateTwoFields(Object bean, ValidatorAction va,
                                        Field field, ActionErrors errors,
                                        HttpServletRequest request) {
    String value =
        ValidatorUtil.getValueAsString(bean, field.getProperty());
    String sProperty2 = field.getVarValue("secondProperty");
    String value2 = ValidatorUtil.getValueAsString(bean, sProperty2);

    if (!GenericValidator.isBlankOrNull(value)) {
        try {
            if (!value.equals(value2)) {
                errors.add(field.getKey(),
                           Resources.getActionError(request, va, field));

                return false;
            }
        } catch (Exception e) {
            errors.add(field.getKey(),
                       Resources.getActionError(request, va, field));

            return false;
        }
    }

    return true;
}

Step 2: Edit validator-rules.xml to contain the "twofields" rule.

<validator name="twofields" 
    classname="org.appfuse.webapp.util.ValidationUtil" method="validateTwoFields" 
    methodParams="java.lang.Object,
                  org.apache.commons.validator.ValidatorAction,
                  org.apache.commons.validator.Field,
                  org.apache.struts.action.ActionErrors,
                  javax.servlet.http.HttpServletRequest" 
   depends="required" msg="errors.twofields">
    <javascript><![CDATA[
        function validateTwoFields(form) {
            var bValid = true;
            var focusField = null;
            var i = 0;
            var fields = new Array();
            oTwoFields = new twofields();
            for (x in oTwoFields) {
                var field = form[oTwoFields[x][0]];
                var secondField = form[oTwoFields[x][2]("secondProperty")];
            
                if (field.type == 'text' ||
                    field.type == 'textarea' ||
                    field.type == 'select-one' ||
                    field.type == 'radio' ||
                    field.type == 'password') {
            
                    var value;
                    var secondValue;
                    // get field's value
                    if (field.type == "select-one") {
                        var si = field.selectedIndex;
                        value = field.options[si].value;
                        secondValue = secondField.options[si].value;
                    } else {
                        value = field.value;
                        secondValue = secondField.value;
                    }
                
                    if (value != secondValue) {
                    
                        if (i == 0) {
                            focusField = field;
                        }
                        fields[i++] = oTwoFields[x][1];
                        bValid = false;
                    }
                }
            }
            
            if (fields.length > 0) {
                focusField.focus();
                alert(fields.join('\n'));
            }
            
            return bValid;
        }]]></javascript>
</validator>

Step 3: Configure validation for your form in validation.xml:

<field property="password"
     depends="required,twofields">
  <msg
    name="required"
    key="errors.required"/>
  <msg
    name="twofields"
    key="errors.twofields"/>

  <arg0 key="userForm.password"/>
  <arg1
    key="userForm.confirmPassword"
  />
  <var>
    <var-name>secondProperty</var-name>
    <var-value>confirmPassword</var-value>
  </var>
</field>

Where errors.twofields=The '{0}' field has to have the same value as the '{1}' field. An alternative to Step 3 is to use XDoclet to generate your validation.xml. This requires (1) configuring XDoclet (of course) and (2) adding some @struts tags to your form on the setPassword method.

/**
 * Returns the password.
 * @return String
 *
 * @struts.validator type="required" msgkey="errors.required"
 * @struts.validator type="twofields" msgkey="errors.twofields"
 * @struts.validator-args arg1resource="userForm.password"
 * @struts.validator-args arg1resource="userForm.confirmPassword"
 * @struts.validator-var name="secondProperty" value="confirmPassword"
 */
public String setPassword() {
	return password;
}

I've sent this as a proposal to the struts-dev mailing list yesterday, but haven't heard anything yet. Enjoy!

Update: You'll need to update ValidationUtil.java and validator-rules-custom.xml for Struts 1.2. Full files: ValidationUtil.java and validation-rules-custom.xml.