These are the standard validators that come with XWork:

All the example XML validation rule snippets below have been put together into one big example here.


RequiredFieldValidator

This validator checks that a field is non-null.

Example:

<validators>
    <field name="user">
        <field-validator type="required">
            <message>You must enter a value for user.</message>
        </field-validator>
    </field>
</validators>


RequiredStringValidator

This validator checks that a String field is not empty (i.e. non-null with a length > 0).

Parameter Required Default Notes
trim no true Boolean property. Determines whether the String is trimmed before performing the length check.

Example:

<validators>
    <field name="userName">
        <field-validator type="requiredstring">
            <message>You must enter an username.</message>
        </field-validator>
    </field>
</validators>


StringLengthFieldValidator

This validator checks that a String field is of the right length. It assumes that the field is a String.

Parameter Required Default Notes
trim no true Boolean property. Determines whether the String is trimmed before performing the length check.
minLength no   Integer property. The minimum length the String must be.
maxLength no   Integer property. The maximum length the String can be.

If neither minLength nor maxLength is set, nothing will be done.

Example:

<validators>
    <field name="userName">
        <field-validator type="stringlength">
            <param name="minLength">3</param>
            <param name="maxLength">10</param>
            <message>Username must be between ${minLength} and ${maxLength} characters long.</message>
        </field-validator>
    </field>
</validators>


StringRegexValidator

This validator checks that a String field matches a configure Regular Expression, if it is not an empty String.

Parameter Required Default Notes
regex yes "." String property. The Regular Expression for which to check a match.
caseSensitive no true Whether the matching of alpha characters in the expression should be done case-sensitively.

Example:

<validators>
    <field name="coords">
        <field-validator type="regex">
            <param name="regex">[0-9],[0-9]</param>
            <message>The value of coords must be in the format "x, y", where x and y are between 0 and 9</message>
        </field-validator>
    </field>
</validators>


EmailValidator

This validator checks that a field is a valid e-mail address if it contains a non-empty String.

Example:

<validators>
    <field name="email">
        <field-validator type="email">
            <message>You must enter a valid email address.</message>
        </field-validator>
    </field>
</validators>


URLValidator

This validator checks that a field is a valid URL.

Example:

<validators>
     <field name="homepage">
        <field-validator type="url">
            <message>You must enter a valid URL.</message>            
        </field-validator>
    </field>
</validators>


IntRangeFieldValidator

This validator checks that a numeric field has a value within a specified range.

Parameter Required Default Notes
min no   Integer property. The minimum the number must be.
max no   Integer property. The maximum number can be.

If neither min nor max is set, nothing will be done.

Example:

<validators>
    <field name="age">
        <field-validator type="int">
            <param name="min">0</param>
            <param name="max">100</param>
            <message>Not a valid age!</message>
        </field-validator>
    </field>
</validators>


DateRangeFieldValidator

This validator checks that a date field has a value within a specified range.

Parameter Required Default Notes
min no   Date property. The minimum the date must be.
max no   Date property. The maximum date can be.

If neither min nor max is set, nothing will be done.

Example:

<validators>
    <field name="startDate">
        <field-validator type="date">
            <param name="min">12/22/2002</param>
            <param name="max">12/25/2002</param>
            <message>The date must be between 12-22-2002 and 12-25-2002.</message>
        </field-validator>
    </field>
</validators>


ConversionErrorFieldValidator

This validator checks if there are any conversion errors for a field and applies them if they exist. See Type Conversion Error Handling for details.

Example:

<validators>
    <field name="startDate">
        <field-validator type="conversion">
            <message>Could not convert input to a valid date.</message>
        </field-validator>
    </field>
</validators>


ExpressionValidator

This validator uses an OGNL expression to perform its validation. The error message will be added to the action if the expression returns false when it is evaluated against the value stack.

Parameter Required Default Notes
expression yes   An OGNL expression that returns a boolean value.

Example:

<validator type="expression">
    <param name="expression">foo > bar</param>
    <message default="Foo must be greater than Bar. Foo = ${foo}, Bar = ${bar}."/>
</validator>


FieldExpressionValidator

This validator uses an OGNL expression to perform its validation. The error message will be added to the field if the expression returns false when it is evaluated against the value stack.

Parameter Required Default Notes
expression yes   An OGNL expression that returns a boolean value.

Example:

<validators>
     <field name="homepage">
        <field-validator type="fieldexpression">
            <param name="expression">homepage.indexOf('opensymphony.com') == -1</param>
            <message>Please provide an OpenSymphony website</message>
        </field-validator>
    </field>
</validators>


VisitorFieldValidator

The validator allows you to forward validation to object properties of your action using the objects own validation files. This allows you to use the ModelDriven development pattern and manage your validations for your models in one place, where they belong, next to your model classes. The VisitorFieldValidator can handle either simple Object properties, Collections of Objects, or Arrays.

The error message for the VisitorFieldValidator will be appended in front of validation messages added by the validations for the Object message.

Parameter Required Default Notes
context no action alias Determines the context to use for validating the Object property. If not defined, the context of the Action validation is propogated to the Object property validation. In the case of Action validation, this context is the Action alias.
appendPrefix no true Determines whether the field name of this field validator should be prepended to the field name of the visited field to determine the full field name when an error occurs. For example, suppose that the bean being validated has a "name" property. If appendPrefix is true, then the field error will be stored under the field "bean.name". If appendPrefix is false, then the field error will be stored under the field "name".
If you are using the VisitorFieldValidator to validate the model from a ModelDriven Action, you should set appendPrefix to false unless you are using "model.name" to reference the properties on your model.

Example:

<validators>
    <field name="user">
        <field-validator type="visitor">
            <param name="context">anotherContext</param>
            <message>user: </message>
        </field-validator>
    </field>
</validators>

Here we see the context being overridden in the validator mapping, so the action alias context will not be propogated.

ModelDriven example:

<validators>
    <field name="model">
        <field-validator type="visitor">
            <param name="appendPrefix">false</param>
            <message />
        </field-validator>
    </field>
</validators>

This will use the model's validation rules and any errors messages will be applied directly (nothing is prefixed because of the empty message).