In the previous algorithm, parameter values were themselves interpolated which was undesirable and could lead to security issue. I have reworked the algorithm to resolve the custom ResourceBundle in priority, the built-in bundle as a back up and finally regular parameters. Check it out 4.3. Message interpolation 4.3.1. Default message interpolation A conforming implementation includes a default message interpolator. This message interpolator shall use the algorithm defined here to interpolate message descriptors into human-readable messages. Each constraint defines a message descriptor via its message property. Every constraint definition shall define a default message descriptor for that constraint. Messages can be overridden at declaration time in constraints by setting the message property on the constraint. The message descriptor is a string literal and may contain one or more message parameters. Message parameters are string literals enclosed in braces. Example 4.1. Message using parameters Value must be between {min} and {max} 4.3.1.1. Algorithm The default message interpolator uses the following steps: Message parameters are extracted from the message string and used as keys to search the ResourceBundle named ValidationMessages (often materialized as the property file/ValidationMessages.properties and its locale variations) using the defined locale (see below). If a property is found, the message parameter is replaced with the property value in the message string. Step 1 is applied recursively until no replacement is performed (ie. a message parameter value can itself contain a message parameter). Message parameters are extracted from the message string and used as keys to search the Bean Validation provider's built-in ResourceBundle using the defined locale (see below). If a property is found, the message parameter is replaced with the property value in the message string. Contrary to step 1, step 2 is not processed recursively. If step 2 triggers a replacement, then step 1 is applied again. Otherwise step 4 is performed. Message parameters are extracted from the message string. Those matching the name of an attribute of the constraint declaration are replaced by the value of that attribute. The defined locale is as followed: if the locale is passed to the interpolator method interpolate(String, CosntraintDescriptor, Object, Locale), this Locale instance is used. otherwise, the default Locale as provided by Locale.getDefault() is used. The proposed algorithm ensures that custom resource bundle always have priority over built-in resource bundle at all level of the recursive resolution. It also ensures that constraint declarations attributes values are not expanded further. 4.3.2. Custom message interpolation A custom message interpolator may be provided (e.g., to interpolate contextual data, or to adjust the default Locale used). A message interpolator implements the MessageInterpolator interface. /** * Interpolate a given constraint violation message. * * @author Emmanuel Bernard * @author Hardy Ferentschik */ public interface MessageInterpolator { /** * Interpolate the message from the constraint parameters and the actual validated object. * The locale is defaulted according to the <code>MessageInterpolator</code> implementation * See the implementation documentation for more detail. * * @param message The message to interpolate. * @param constraintDescriptor The constraint descriptor. * @param value The object being validated * * @return Interpolated error message. */ String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value); /** * Interpolate the message from the constraint parameters and the actual validated object. * The Locale used is provided as a parameter * * @param message The message to interpolate. * @param constraintDescriptor The constraint descriptor. * @param value The object being validated * @param locale the locale targeted for the message * * @return Interpolated error message. */ String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value, Locale locale); } message is the message descriptor as seen in @ConstraintAnnotation.message or provided to the ConstraintContext methods. constraintDescriptor is the ConstraintDescriptor object representing the metadata of the failing constraint (see Constraint metadata request API). value is the value being validated. MessageInterpolator.interpolate(String, ConstraintDescriptor, Object) is invoked by for each constraint violation report generated. The default Locale is implementation specific. MessageInterpolator.interpolate(String, ConstraintDescriptor, Object, Locale) can be invoked by a wrapping MessageInterpolator to enforce a specific Locale value by bypassing or overriding the default Locale strategy. A message interpolator implementation shall be threadsafe. The message interpolator is provided to the ValidatorFactory at construction time using ValidatorFactoryBuilder.messageInterpolator(MessageInterpolator). This message interpolator is shared by all validators generated by this ValidatorFactory. It is possible to override the MessageInterpolator implementation for a given Validator instance by invokingValidatorFactory .defineValidatorState ().messageInterpolator(messageInterpolator).getValidator(). It is recommended that MessageInterpolator implementations delegate final interpolation to the Bean Validation default MessageInterpolator to ensure standard Bean Validation interpolation rules are followed, The default implementation is accessible through ValidatorFactoryBuilder.getDefaultMessageInterpolator(). 4.3.3. Examples These examples describe message interpolation based on the default message interpolator's built-in messages (see Appendix B, Standard ResourceBundle messages), and the ValidationMessages.propertiesfile shown in table Table 4.2, “message interpolation”. The current locale is assumed English. //ValidationMessages.properties myapp.creditcard.error=credit card number not valid Table 4.2. message interpolation Failing constraint declaration interpolated message @NotNull must not be null @Max(30) must be less than or equal to 30 @Size(min=5, max=15, message="Key must have between {min} and {max} characters") Key must have between 5 and 15 characters @Digits(integer=9, fraction=2) numeric value out of bounds (<9 digits>.<2 digits> expected) @CreditCard(message={myapp.creditcard.error}) credit card number not valid Here is an approach to specify the Locale value to choose on a given Validator. Locale aware MessageInterpolator. See Section 4.4, “Bootstrapping” for more details on the APIs. Example 4.2. Use MessageInterpolator to use a specific Locale value /** * delegates to a MessageInterpolator implementation but enforce a given Locale */ public class LocaleSpecificMessageInterpolator implements MessageInterpolator { private final MessageInterpolator defaultInterpolator; private final Locale defaultLocale; public LocaleSpecificMessageInterpolator(MessageInterpolator interpolator, Locale locale) { this.defaultLocale = locale; this.defaultInterpolator = interpolator; } /** * enforece the locale passed to the interpolator */ public String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value) { return defaultInterpolator.interpolate(message, constraintDescriptor, value, this.defaultLocale); } // no real use, implemented for completeness public String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value, Locale locale) { return defaultInterpolator.interpolate(message, constraintDescriptor, value, locale); } } Locale locale = getMyCurrentLocale(); MessageInterpolator interpolator = new LocaleSpecificMessageInterpolator( validatorFactory.getMessageInterpolator(), locale); Validator validator = validatorFactory.defineValidatorState() .messageInterpolator (interpolator) .getValidator(); Most of the time, however, the relevant Locale will be provided by your application framework transparently. This framework will implement its own version of MessageInterpolator and pass it during theValidatorFactory configuration. The application will not have to set the Locale itself. This example shows how a container framework would implement MessageInterpolator to provide a user specific default locale. Example 4.3. Contextual container possible MessageInterpolator implementation public class ContextualMessageInterpolator { private final MessageInterpolator delegate; public ContextualMessageInterpolator(MessageInterpolator delegate) { this.delegate = delegate; } public String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value) { Locale locale = Container.getManager().getUserLocale(); return this.delegate.interpolate( message, constraintDescriptor, value, locale ); } public String interpolate(String message, ConstraintDescriptor constraintDescriptor, Object value, Locale locale) { return this.delegate.interpolate(message, constraintDescriptor, value, locale); } } //Build the ValidatorFactory ValidatorFactoryBuilder builder = Validation.getBuilder(); ValidatorFactory factory = builder .messageInterpolator( new ContextualMessageInterpolator ( builder.getDefaultMessageInterpolator() ) ) .build(); //The container uses the factory to validate constraints using the specific MessageInterpolator Validator validator = factory.getValidator();