    001//  Copyright 2008 The Apache Software Foundation
    002//
    003// Licensed under the Apache License, Version 2.0 (the "License");
    004// you may not use this file except in compliance with the License.
    005// You may obtain a copy of the License at
    006//
    007//     http://www.apache.org/licenses/LICENSE-2.0
    008//
    009// Unless required by applicable law or agreed to in writing, software
    010// distributed under the License is distributed on an "AS IS" BASIS,
    011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012// See the License for the specific language governing permissions and
    013// limitations under the License.
    014
    015package org.apache.tapestry5;
    016
    017/**
    018 * A wrapper around {@link org.apache.tapestry5.Translator} that combines the translator for a specific {@link
    019 * org.apache.tapestry5.Field} and (sometimes) an override of the default validation message (used when an input value
    020 * can't be parsed).
    021 */
    022public interface FieldTranslator<T>
    023{
    024    /**
    025     * Returns the type of the server-side value.
    026     *
    027     * @return a type
    028     */
    029    Class<T> getType();
    030
    031    /**
    032     * Invoked after the client-submitted value has been {@link Translator translated} to check that the value conforms
    033     * to expectations (often, in terms of minimum or maximum value). If and only if the value is approved by all
    034     * Validators is the value applied by the field.
    035     *
    036     * @throws ValidationException if the value violates the constraint
    037     */
    038    T parse(String input) throws ValidationException;
    039
    040    /**
    041     * Converts a server-side value to a client-side string. This allows for formatting of the value in a way
    042     * appropriate to the end user.
    043     *
    044     * @param value the server side value (which will not be null)
    045     * @return client-side value to present to the user
    046     * @see Translator#toClient(Object)
    047     */
    048    String toClient(T value);
    049
    050    /**
    051     * Invokes {@link Translator#render(Field, String, MarkupWriter,org.apache.tapestry5.services.FormSupport)}. This is
    052     * called at a point "inside" the tag, so that additional attributes may be added.  In many cases, the underlying
    053     * {@link org.apache.tapestry5.Validator} may write client-side JavaScript to enforce the constraint as well.
    054     *
    055     * @param writer markup writer to direct output to.
    056     * @see org.apache.tapestry5.MarkupWriter#attributes(Object[])
    057     */
    058    void render(MarkupWriter writer);
    059}