| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package org.apache.tapestry5; |
| |
| import org.apache.tapestry5.ioc.MessageFormatter; |
| import org.apache.tapestry5.services.FormSupport; |
| |
| /** |
| * Used by a {@link Field} to enforce a <strong>constraint</strong> related to a form submission. Validators themselves |
| * are stateless singletons. |
| * |
| * Validators are usually encapsulated inside a {@link FieldValidator}. |
| * |
| * @see FieldValidationSupport |
| * @see org.apache.tapestry5.services.FieldValidatorDefaultSource |
| */ |
| public interface Validator<C, T> |
| { |
| /** |
| * Returns the type of constraint value used with this validator. Constraint values are used to parameterize a |
| * validator, for example a "maxLength" validator will have a constraint value of type int (the maximum length |
| * allowed). For constraints that do not have a constraint value, this method returns null. |
| */ |
| Class<C> getConstraintType(); |
| |
| /** |
| * Returns the value type associated with this validator. {@link #validate(Field, Object, MessageFormatter, Object)} |
| * will only be invoked when the value is assignable to the validator's value type. |
| */ |
| Class<T> getValueType(); |
| |
| /** |
| * Returns the message key, within the validation messages, normally used by this validator. This is used to provide |
| * the {@link MessageFormatter} passed to {@link #validate(Field, Object, MessageFormatter, Object)} (unless |
| * overridden). |
| * |
| * @return a message key |
| */ |
| String getMessageKey(); |
| |
| /** |
| * Invoked after the client-submitted value has been {@link org.apache.tapestry5.Translator translated} to check |
| * that the value conforms to expectations (often, in terms of minimum or maximum value). If and only if the value |
| * is approved by all Validators is the value applied by the field. |
| * |
| * @param field the field for which a client submitted value is being validated |
| * @param constraintValue the value used to constrain |
| * @param formatter Validation messages, in the appropriate locale |
| * @param value the translated value supplied by the user |
| * @throws ValidationException if the value violates the constraint |
| */ |
| void validate(Field field, C constraintValue, MessageFormatter formatter, T value) throws ValidationException; |
| |
| /** |
| * Returns true if the validator should be invoked for null or blank (empty string) values. This is generally false, |
| * but is true for validators that enforce that a non-blank value is required. This is the basis of the {@link |
| * org.apache.tapestry5.Field#isRequired()} property. |
| */ |
| boolean isRequired(); |
| |
| /** |
| * Hook used by components to allow the validator to contribute additional attributes or (more often) client-side |
| * JavaScript (via the {@link FormSupport#addValidation(Field, String, String, Object)}). |
| * |
| * @param field the field which is currently being rendered |
| * @param constraintValue the value used to constrain input |
| * @param formatter validation message, in the appropriate locale |
| * @param writer markup writer, allowing additional attributes to be written into the active element |
| * @param formSupport used to add JavaScript |
| */ |
| void render(Field field, C constraintValue, MessageFormatter formatter, MarkupWriter writer, |
| FormSupport formSupport); |
| } |