    001// Copyright 2009, 2012 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.services;
    016
    017import java.io.IOException;
    018import java.io.ObjectInputStream;
    019
    020/**
    021 * A service used when a component or service needs to encode some amount of data on the client as a string. The string
    022 * may be a query parameter, hidden form field, or a portion of a URL.  The default implementation converts the object
    023 * output stream into a Base64 string.
    024 * <p/>
    025 * Starting in release 5.3.6, the encoded data incorporates an HMAC (hash based message authentication code) signature,
    026 * as a prefix. HMAC requires a secret key, configured using the
    027 * {@link org.apache.tapestry5.SymbolConstants#HMAC_PASSPHRASE} symbol.
    028 *
    029 * @since 5.1.0.1
    030 */
    031public interface ClientDataEncoder
    032{
    033    /**
    034     * Creates a sink for client data.  The sink provides an output stream and ultimately, a string representation of
    035     * the data sent to the stream.
    036     *
    037     * @return a new sink
    038     */
    039    ClientDataSink createSink();
    040
    041    /**
    042     * Decodes data previously obtained from {@link ClientDataSink#getClientData()}.
    043     *
    044     * @param clientData
    045     *         encoded client data
    046     * @return stream of decoded data
    047     * @throws IOException
    048     *         if the client data has been corrupted (verified via the HMAC)
    049     */
    050    ObjectInputStream decodeClientData(String clientData) throws IOException;
    051
    052    /**
    053     * Decodes client data obtained via {@link ClientDataSink#getEncodedClientData()}.
    054     *
    055     * @param clientData
    056     *         URLEncoded client data
    057     * @return stream of objects
    058     * @throws IOException
    059     *         if the client data has been corrupted (verified via the HMAC)
    060     * @since 5.1.0.4
    061     */
    062    ObjectInputStream decodeEncodedClientData(String clientData) throws IOException;
    063}