    001// Copyright 2006, 2008, 2011 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
    017import org.apache.tapestry5.services.FormSupport;
    018
    019/**
    020 * Translates between client-side and server-side values. Client-side values are always strings.
    021 *
    022 * @param <T> the type being translated
    023 * @see org.apache.tapestry5.services.TranslatorSource
    024 * @see org.apache.tapestry5.FieldValidationSupport
    025 * @see org.apache.tapestry5.FieldTranslator
    026 */
    027public interface Translator<T>
    028{
    029    /**
    030     * Returns a unique name for the translator. This is used to identify the translator by name, but is also used when
    031     * locating override messages for the translator.
    032     *
    033     * @return unique name for the translator
    034     */
    035    String getName();
    036
    037    /**
    038     * Converts a server-side value to a client-side string. This allows for formatting of the value in a way
    039     * appropriate to the end user. The output client value should be parsable by
    040     * {@link #parseClient(Field, String, String)}.
    041     *
    042     * @param value
    043     *            the server side value (which will not be null)
    044     * @return client-side value to present to the user
    045     */
    046    String toClient(T value);
    047
    048    /**
    049     * Returns the type of the server-side value.
    050     *
    051     * @return a type
    052     */
    053    Class<T> getType();
    054
    055    /**
    056     * Returns the message key, within the application's global message catalog, normally used by this validator. This
    057     * is used to provide the formatted message to {@link #parseClient(Field, String, String)} or
    058     * {@link #render(Field, String, MarkupWriter, org.apache.tapestry5.services.FormSupport)}.
    059     *
    060     * @return a message key
    061     */
    062    String getMessageKey();
    063
    064    /**
    065     * Converts a submitted request value into an appropriate server side value.
    066     *
    067     * @param field
    068     *            for which a value is being parsed
    069     * @param clientValue
    070     *            to convert to a server value; this will not be null, but may be blank
    071     * @param message
    072     *            formatted validation message, either from validation messages, or from an override
    073     * @return equivalent server-side value (possibly null)
    074     * @throws ValidationException
    075     *             if the value can not be parsed
    076     */
    077    T parseClient(Field field, String clientValue, String message) throws ValidationException;
    078
    079    /**
    080     * Hook used by components to allow the validator to contribute additional attributes or (more often) client-side
    081     * JavaScript (via the
    082     * {@link org.apache.tapestry5.services.FormSupport#addValidation(Field, String, String, Object)}).
    083     *
    084     * @param field
    085     *            the field which is currently being rendered
    086     * @param message
    087     *            formatted validation message, either from validation messages, or from an override
    088     * @param writer
    089     *            markup writer, allowing additional attributes to be written into the active element
    090     * @param formSupport
    091     *            used to add JavaScript
    092     */
    093    void render(Field field, String message, MarkupWriter writer, FormSupport formSupport);
    094}