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Bean validation involves validating user input using Tapestry's built-in support for the JSR 303 Bean Validation API.

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Tapestry has always provided a powerful non-JSR 303 validation mechanism (see Forms and Bean Validation). Among other things this mechanism allows you to annotate your domain model classes with the @Validate annotation. However, this annotation is problematic if your domain model is used in non-Tapestry applications as well as in Tapestry applications. Your non-Tapestry application becomes dependent on tapestry5-annotations module. To make your domain model independent from Tapestry you can use the JSR 303: Bean Validation instead. This library provides integration between Tapestry and JSR-303.

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The BeanValidatorSource service is responsible for bootstrapping the Validator. You can contribute a BeanValidatorConfigurer to the configuration of this service in order to participate on the configuration of Validator.

Code Block

language	java

@Contribute(BeanValidatorSource.class)
public static void provideBeanValidatorConfigurer(OrderedConfiguration<BeanValidatorConfigurer> configuration)
{
   configuration.add("MyConfigurer", new BeanValidatorConfigurer()
   {
      public void configure(javax.validation.Configuration<?> configuration)
      {
         configuration.ignoreXmlConfiguration();
      }
   });
}

Validation groups

In JSR-303 validation groups are used to define a subset of the constraints validated at a given time. If no validation group is specified the Default group is taken. By default, Tapestry passes only this group to Validator. You can tell Tapestry to pass more groups by contributing group classes into the configuration of the BeanValidatorSource service.

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Once you included this library and its dependencies into your web app, you may use the JSR-303 annotations to validate the user's input.

Code Block

language	java

public class Login
{
   @NotNull
   @Size(max=10)
   @Pattern(regexp = "[a-zA-Z]*")
   @Property @Persist
   private String userName;

   @NotNull
   @Size(min=5, max=30)
   @Property @Persist
   private String password;

   void onSuccess()
   {
      // Login the user here
   }
}

You can even mix JSR-303 annotations and Tapestry's @Validate annotation.

Code Block

language	java

public class Login
{
   @NotNull
   @Validate("maxlength=10")
   @Pattern(regexp = "[a-zA-Z]*")
   @Property @Persist
   private String userName;

   @NotNull
   @Validate("minlength=5,maxlength=30")
   @Property @Persist
   private String password;

   void onSuccess()
   {
      // Login the user here
   }
}

Next you have to pass the object to validate into the Form's validate parameter. In the following example the Form's fields are bound to the properties of the Login page. That's why we pass this, thus the page instance, to the validate parameter.

Code Block

language	xml

<html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_1_0.xsd">
   <body>
      <t:form validate="this">

         <t:errors/>

         <p>
            <t:textfield t:id="userName"/>
         </p>

         <p>
            <t:textfield t:id="password"/>
         </p>

         <p>
            <input type="submit" value="Login"/>
         </p>
      <t:form>
   </body>
</html>

Since the validate parameter defaults to the container of the Form component, we could also remove validate="this" in the example above.

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If you use the BeanEditForm component it's even easier to validate your beans. The only thing you have to do is to annotate your beans with JSR-303 annotations. If you are migrating from Tapestry's built-in validation mechanism to JSR-303 Bean Validation, you don't have to change your template at all.

Code Block

language	java

public class User
{
   @NotNull
   private String userName;

   @NotNull
   @Validate("minlength=10")
   private String password;

   ...
}

Client-side Validation

Unfortunately JSR-303 doesn’t cover client-side validation, so web frameworks supporting this JSR need to come up with proprietary client-side solutions. Tapestry provides client-side validation for the following JSR-303 constraints:

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Now let's see how to provide own client-side validation for JSR-303 constraints. Imagine you created the following constraint definition. The server-side implementation of the constraint is implemented by RangeValidator. I suppose you are familiar with JSR-303, so I don’t explain how to implement RangeValidator.

Code Block

language	java

@Documented
@Constraint(validatedBy = RangeValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface Range {
   long max() default Long.MAX_VALUE;

   long min() default Long.MIN_VALUE;

   String message() default "{com.acme.constraint.Range.message}";

   Class[] groups() default {};

   Class[] payload() default {};
}

To provide client-side validation of a constraint you have to add a JavaScript function to the built-in Tapestry.Validator JavaScript-object. The function should contain exactly three parameters:

Field being validated
Validation message
JSON object with values from the constraint annotation

Here is an example:

Code Block

language	js

Tapestry.Validator.range = function(field, message, spec) {
   field.addValidator(function(value) {
      if (value < spec.min || value > spec.max) {
         throw message;
      }
   });
};

Now you have to tell Tapestry to call the function Tapestry.Validator.range when client-side validation of @Range should be executed. This is accomplished by a contribution to the ClientConstraintDescriptorSource service. The configuration of this service is a collection of ClientConstraintDescriptor. Each ClientConstraintDescriptor represents a client-side validation constraint. The constructor of ClientConstraintDescriptor has three parameters:

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The last step is to make the contribution, which links the @Range annotation with the JavaScript function range. The attributes max and min and their values are passed to the function.

Code Block

language	java

@Contribute(ClientConstraintDescriptorSource.class)
public static void provideClientConstraintDescriptors(Configuration<ClientConstraintDescriptor> config) {

   config.add(new ClientConstraintDescriptor(Range.class, "range", "min", "max"));
}

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Validation groups

Client-side Validation