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JSR 356: Java API for WebSocket
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/*
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 *
 * Copyright (c) 2012-2013 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * http://glassfish.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
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 * file and include the License file at packager/legal/LICENSE.txt.
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 * GPL Classpath Exception:
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 *
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package javax.websocket;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.ByteBuffer;

/**
 * The Decoder interface holds member interfaces that define how a developer can provide
 * the web socket container a way web socket messages into developer defined custom objects.
 * The websocket implementation creates a new instance of the decoder per endpoint instance per connection.
 *
 * @author dannycoward
 * @since DRAFT 002
 */
public interface Decoder {

    /**
     * This interface defines how a custom object (of type T) is decoded from a web socket message in
     * the form of a byte buffer.
     */
    interface Binary extends Decoder {

        /**
         * Decode the given bytes into an object of type T.
         *
         * @param bytes the bytes to be decoded.
         * @return the decoded object.
         */
        T decode(ByteBuffer bytes) throws DecodeException;

        /**
         * Answer whether the given bytes can be decoded into an object of type T.
         *
         * @param bytes the bytes to be decoded.
         * @return whether or not the bytes can be decoded by this decoder.
         */
        boolean willDecode(ByteBuffer bytes);
    }

    /**
     * This interface defines how a custom object is decoded from a web socket message in
     * the form of a binary stream.
     */
    interface BinaryStream extends Decoder {

        /**
         * Decode the given bytes read from the input stream into an object of type T.
         *
         * @param is the input stream carrying the bytes.
         * @return the decoded object.
         */
        T decode(InputStream is) throws DecodeException, IOException;
    }

    /**
     * This interface defines how a custom object is decoded from a web socket message in
     * the form of a string.
     */
    interface Text extends Decoder {
        /**
         * Decode the given String into an object of type T.
         *
         * @param s string to be decoded.
         * @return the decoded message as an object of type T
         */
        T decode(String s) throws DecodeException;

        /**
         * Answer whether the given String can be decoded into an object of type T.
         *
         * @param s the string being tested for decodability.
         * @return whether this decoder can decoded the supplied string.
         */
        boolean willDecode(String s);
    }

    /**
     * This interface defines how a custom object of type T is decoded from a web socket message in
     * the form of a character stream.
     */
    interface TextStream extends Decoder {
        /**
         * Reads the websocket message from the implementation provided
         * Reader and decodes it into an instance of the supplied object type.
         *
         * @param reader the reader from which to read the web socket message.
         * @return the instance of the object that is the decoded web socket message.
         */
        T decode(Reader reader) throws DecodeException, IOException;
    }
}