    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
    015    package org.apache.tapestry5.services;
    016
    017    import java.io.IOException;
    018    import 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     */
    031    public 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    }