ByteToMessageCodec Class — netty Architecture

Source Code

codec-base/src/main/java/io/netty/handler/codec/ByteToMessageCodec.java lines 34–179

public abstract class ByteToMessageCodec<I> extends ChannelDuplexHandler {

    private final TypeParameterMatcher outboundMsgMatcher;
    private final MessageToByteEncoder<I> encoder;

    private final ByteToMessageDecoder decoder = new ByteToMessageDecoder() {
        @Override
        public void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
            ByteToMessageCodec.this.decode(ctx, in, out);
        }

        @Override
        protected void decodeLast(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
            ByteToMessageCodec.this.decodeLast(ctx, in, out);
        }
    };

    /**
     * see {@link #ByteToMessageCodec(boolean)} with {@code true} as boolean parameter.
     */
    protected ByteToMessageCodec() {
        this(true);
    }

    /**
     * see {@link #ByteToMessageCodec(Class, boolean)} with {@code true} as boolean value.
     */
    protected ByteToMessageCodec(Class<? extends I> outboundMessageType) {
        this(outboundMessageType, true);
    }

    /**
     * Create a new instance which will try to detect the types to match out of the type parameter of the class.
     *
     * @param preferDirect          {@code true} if a direct {@link ByteBuf} should be tried to be used as target for
     *                              the encoded messages. If {@code false} is used it will allocate a heap
     *                              {@link ByteBuf}, which is backed by an byte array.
     */
    protected ByteToMessageCodec(boolean preferDirect) {
        ensureNotSharable();
        outboundMsgMatcher = TypeParameterMatcher.find(this, ByteToMessageCodec.class, "I");
        encoder = new Encoder(preferDirect);
    }

    /**
     * Create a new instance
     *
     * @param outboundMessageType   The type of messages to match
     * @param preferDirect          {@code true} if a direct {@link ByteBuf} should be tried to be used as target for
     *                              the encoded messages. If {@code false} is used it will allocate a heap
     *                              {@link ByteBuf}, which is backed by an byte array.
     */
    protected ByteToMessageCodec(Class<? extends I> outboundMessageType, boolean preferDirect) {
        ensureNotSharable();
        outboundMsgMatcher = TypeParameterMatcher.get(outboundMessageType);
        encoder = new Encoder(preferDirect, outboundMessageType);
    }

    /**
     * Returns {@code true} if and only if the specified message can be encoded by this codec.
     *
     * @param msg the message
     */
    public boolean acceptOutboundMessage(Object msg) throws Exception {
        return outboundMsgMatcher.match(msg);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        decoder.channelRead(ctx, msg);
    }

    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        encoder.write(ctx, msg, promise);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        decoder.channelReadComplete(ctx);
    }