Validation

WebWork relies on XWork's validation framework to enable the application of input validation rules to your Actions before they are executed. This section only provides the bare minimum to get you started and focuses on WebWork's extension of the XWork validators to support client-side validation.

Please consult XWork's validation framework documentation for complete details.

Reference pages

1. Simple validators
2. Visitor validation
3. Client-Side Validation
4. Validation Examples

Registering Validators

Validation rules are handled by validators, which must be registered with the ValidatorFactory. The simplest way to do so is to add a file name validators.xml in the root of the classpath (/WEB-INF/classes) that declares all the validators you intend to use. The syntax of the file is as follows:

<validators>
    <validator name="required" 
        class="com.opensymphony.webwork.validators.JavaScriptRequiredFieldValidator"/>
    <validator name="requiredstring"
        class="com.opensymphony.webwork.validators.JavaScriptRequiredStringValidator"/>
    <validator name="stringlength"
        class="com.opensymphony.xwork.validator.validators.StringLengthFieldValidator"/>
    <validator name="int"
        class="com.opensymphony.webwork.validators.JavaScriptIntRangeFieldValidator"/>
    <validator name="date"
        class="com.opensymphony.webwork.validators.JavaScriptDateRangeFieldValidator"/>
    <validator name="expression"
        class="com.opensymphony.xwork.validator.validators.ExpressionValidator"/>
    <validator name="fieldexpression"
        class="com.opensymphony.xwork.validator.validators.FieldExpressionValidator"/>
    <validator name="email"
        class="com.opensymphony.webwork.validators.JavaScriptEmailValidator"/>
    <validator name="url"
        class="com.opensymphony.webwork.validators.JavaScriptURLValidator"/>
    <validator name="visitor"
        class="com.opensymphony.xwork.validator.validators.VisitorFieldValidator"/>
    <validator name="conversion"
        class="com.opensymphony.xwork.validator.validators.ConversionErrorFieldValidator"/>
    <validator name="regex" 
        class="com.opensymphony.xwork.validator.validators.RegexFieldValidator"/>
</validators>

This list declares all the validators that comes with WebWork.

Turning on Validation

All that is required to enable validation for an Action is to put the ValidationInterceptor in the interceptor refs of the action (see xwork.xml) like so:

<interceptor name="validator" class="com.opensymphony.xwork.validator.ValidationInterceptor"/>

Note: The default validationWorkflowStack already includes this.

Validator Scopes

Field validators, as the name indicate, act on single fields accessible through an action. A validator, in contrast, is more generic and can do validations in the full action context, involving more than one field (or even no field at all) in validation rule.
Most validations can be defined on per field basis. This should be preferred over non-field validation whereever possible, as field validator messages are bound to the related field and will be presented next to the corresponding input element in the respecting view. Non-field validators only add action level messages.
Non-field validators are mostly domain specific and therefore often custom implementations. The most important standard non-field validator provided by XWork/WebWork is ExpressionValidator.

Defining Validation Rules

Validation rules can be specified:

1. Per Action class: in a file named ActionName-validation.xml
2. Per Action alias: in a file named ActionName-alias-validation.xml
3. Inheritance hierarchy and interfaces implemented by Action class: WebWork searches up the inheritance tree of the action to find default validations for parent classes of the Action and interfaces implemented

Here is an example for SimpleAction-validation.xml:

<!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0//EN"
        "http://www.opensymphony.com/xwork/xwork-validator-1.0.dtd">
<validators>
    <field name="bar">
        <field-validator type="required">
            <message>You must enter a value for bar.</message>
        </field-validator>
        <field-validator type="int">
            <param name="min">6</param>
            <param name="max">10</param>
            <message>bar must be between ${min} and ${max}, current value is ${bar}.</message>
        </field-validator>
    </field>
    <field name="bar2">
        <field-validator type="regex">
            <param name="regex">[0-9],[0-9]</param>
            <message>The value of bar2 must be in the format "x, y", where x and y are between 0 and 9</message>
        </field-validator>
    </field>
    <field name="date">
        <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>
    <field name="foo">
        <field-validator type="int">
            <param name="min">0</param>
            <param name="max">100</param>
            <message key="foo.range">Could not find foo.range!</message>
        </field-validator>
    </field>
    <validator type="expression">
        <param name="expression">foo > bar</param>
        <message>Foo must be greater than Bar. Foo = ${foo}, Bar = ${bar}.</message>
    </validator>
</validators>

Here we can see the configuration of validators for the SimpleAction class. Validators (and field-validators) must have a type attribute, which refers to a name of an Validator registered with the ValidatorFactory as above. Validator elements may also have <param> elements with name and value attributes to set arbitrary parameters into the Validator instance. See below for discussion of the message element.

Each Validator or Field-Validator element must define one message element inside the validator element body. The message element has 1 attributes, key which is not required. The body of the message tag is taken as the default message which should be added to the Action if the validator fails.

Key gives a message key to look up in the Action's ResourceBundles using getText() from LocaleAware if the Action implements that interface (as ActionSupport does). This provides for Localized messages based on the Locale of the user making the request (or whatever Locale you've set into the LocaleAware Action).

After either retrieving the message from the ResourceBundle using the Key value, or using the Default message, the current Validator is pushed onto the ValueStack, then the message is parsed for ${...} sections which are replaced with the evaluated value of the string between the ${ and }. This allows you to parameterize your messages with values from the Validator, the Action, or both. Here is an example of a parameterized message:

bar must be between ${min} and ${max}, current value is ${bar}.

This will pull the min and max parameters from the IntRangeFieldValidator and the value of bar from the Action.