Intro

The Intro page provides an overview and describes the motivation for the features described below. This page explains the most important APIs and mechanisms of the property validation module provided by ExtVal. Please note that this page doesn't show all possibilities. If you have any question, please contact the community!

Dependencies

The page ExtVal Modules provides an overview about ExtVal modules and how to add them to your project.

For using the features described in this page, you have to add the core and the property validation module for the JSF version you are using.

Hello-World example

Setup

Required steps for using ExtVal:

• Download the required ExtVal jar-files or checkout the Source Code and build it. (details)
• Add these jar-files to your classpath (manually or via maven)
• Use the annotations (details)

That's it!

The sample page

The sample bean

The result

Available annotations

Simple validation

JPA based validation

JPA annotations are used automatically for UI validation as soon as you:

• Add myfaces-extval-core-.jar and myfaces-extval-property-validation-.jar to the classpath
• Use JPA annotations within the model (e.g.: @Column(nullable = false) -> the field is required)

That's it!

(A simple demo is available here: demo_000)

Cross-Validation

Existing/3rd party constraints

ExtVal has no special requirements for annotations. It's the responsibility of the validation strategy to know how to validate the annotation.
So you can use annotations within any layer without introducing an ExtVal dependency below the view layer.
If you would like to validate 3rd party annotations you can provide a mapping. With the same mechanism you can replace existing (ExtVal) validation strategies. Find detailed information below.

Custom annotations

ExtVal provides the possibility to validate annotations with so called validation strategies.

The simplest case is to create a custom annotation and to use a name convention for the validator (= validation strategy).
The validation strategy has to implement the ValidationStrategy interface. Or you can extend a class which implements this interface in-/directly. (A simple demo is available here: demo_002, demo_006)

//my.custom.package.CustomConstraint

@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface CustomConstraint
{
}

//my.custom.package.CustomConstraintValidationStrategy
public class CustomConstraintValidationStrategy implements ValidationStrategy
{
    void validate(FacesContext facesContext, UIComponent uiComponent,
                  MetaDataEntry metaDataEntry, Object convertedObject)
    {
        //custom validation logic
    }
}

That's just the simplest case. You can also use one of the other available name conventions or you can provide a custom convention or a custom name mapper or ...

Provide/replace validation strategy mappings

If you don't like to use the name mapping concept, you can provide static mappings between annotations and validation strategies.
Use the convention for a mapping file ( org.apache.myfaces.extensions.validator.custom.strategy_mappings.properties ) (it's customizable)

or use the ExtVal Java API:

Register a resource-bundle file which contains an annotation/validation strategy mapping:

StaticConfiguration<String, String> staticConfig = new StaticResourceBundleConfiguration();
staticConfig.setSourceOfMapping("[custom package + name of the properties file.]");
ExtValContext.getContext().addStaticConfiguration(StaticConfigurationNames.META_DATA_TO_VALIDATION_STRATEGY_CONFIG, staticConfig);

It's also used internally to provide the JPA based validation support. So you can find an example at the PropertyValidationModuleStartupListener.
A similar approach is used internally by the annotation based config extension

This approach is more typesafe - a simple example:

StaticInMemoryConfiguration staticConfig = new StaticInMemoryConfiguration();
staticConfig.addMapping(CustomConstraint.class.getName(), CustomValidator.class.getName());
ExtValContext.getContext().addStaticConfiguration(StaticConfigurationNames.META_DATA_TO_VALIDATION_STRATEGY_CONFIG, staticConfig);

I18N support

see Internationalization

Spring support

It's possible to provide a validation strategy as Spring bean.

Use-cases:

• Inject a Spring bean into the validation strategy
• AOP exception handling
• ...

<!-- The name of annotation: @CustomRequired -->

<!-- Part of the Spring configuration: -->

<bean id="customRequiredValidationStrategy" class="..." lazy-init="true">
    <property name="messageResolver" ref="customMsgResolver"/>
    <property name="requiredValidationService" ref="demoRequiredValidationService"/>
</bean>

<bean id="customMsgResolver" 
      class="org.apache.myfaces.extensions.validator.core.validation.message.resolver.DefaultValidationErrorMessageResolver"
      lazy-init="true">

    <!-- With JSF 1.2 you can use the var name of resource-bundle see faces-config.xml -->
    <property name="messageBundleVarName" value="messages"/>
</bean>

<bean id="demoRequiredValidationService" class="..."/>

The bean name follows the available name conventions.
(Also custom name conventions are supported.)

A simple demo is available here: demo_106

Furthermore, it's possible to provide a Meta-Data Transformer as Spring bean.