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}