    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.services;
    014
    015import java.io.IOException;
    016import java.io.ObjectInputStream;
    017
    018/**
    019 * A service used when a component or service needs to encode some amount of data on the client as a string. The string
    020 * may be a query parameter, hidden form field, or a portion of a URL.  The default implementation converts the object
    021 * output stream into a Base64 string.
    022 *
    023 * Starting in release 5.3.6, the encoded data incorporates an HMAC (hash based message authentication code) signature,
    024 * as a prefix. HMAC requires a secret key, configured using the
    025 * {@link org.apache.tapestry5.SymbolConstants#HMAC_PASSPHRASE} symbol.
    026 *
    027 * @since 5.1.0.1
    028 */
    029public interface ClientDataEncoder
    030{
    031    /**
    032     * Creates a sink for client data.  The sink provides an output stream and ultimately, a string representation of
    033     * the data sent to the stream.
    034     *
    035     * @return a new sink
    036     */
    037    ClientDataSink createSink();
    038
    039    /**
    040     * Decodes data previously obtained from {@link ClientDataSink#getClientData()}.
    041     *
    042     * @param clientData
    043     *         encoded client data
    044     * @return stream of decoded data
    045     * @throws IOException
    046     *         if the client data has been corrupted (verified via the HMAC)
    047     */
    048    ObjectInputStream decodeClientData(String clientData) throws IOException;
    049
    050    /**
    051     * Decodes client data obtained via {@link ClientDataSink#getEncodedClientData()}.
    052     *
    053     * @param clientData
    054     *         URLEncoded client data
    055     * @return stream of objects
    056     * @throws IOException
    057     *         if the client data has been corrupted (verified via the HMAC)
    058     * @since 5.1.0.4
    059     */
    060    ObjectInputStream decodeEncodedClientData(String clientData) throws IOException;
    061}