BrotliEncoder Class — netty Architecture

Source Code

codec-compression/src/main/java/io/netty/handler/codec/compression/BrotliEncoder.java lines 42–279

@ChannelHandler.Sharable
public final class BrotliEncoder extends MessageToByteEncoder<ByteBuf> {

    private static final AttributeKey<Writer> ATTR = AttributeKey.valueOf("BrotliEncoderWriter");

    private final Encoder.Parameters parameters;
    private final boolean isSharable;
    private Writer writer;

    /**
     * Create a new {@link BrotliEncoder} Instance with {@link BrotliOptions#DEFAULT}
     * and {@link #isSharable()} set to {@code true}
     */
    public BrotliEncoder() {
        this(BrotliOptions.DEFAULT);
    }

    /**
     * Create a new {@link BrotliEncoder} Instance
     *
     * @param brotliOptions {@link BrotliOptions} to use and
     *                      {@link #isSharable()} set to {@code true}
     */
    public BrotliEncoder(BrotliOptions brotliOptions) {
        this(brotliOptions.parameters());
    }

    /**
     * Create a new {@link BrotliEncoder} Instance
     * and {@link #isSharable()} set to {@code true}
     *
     * @param parameters {@link Encoder.Parameters} to use
     */
    public BrotliEncoder(Encoder.Parameters parameters) {
        this(parameters, true);
    }

    /**
     * <p>
     * Create a new {@link BrotliEncoder} Instance and specify
     * whether this instance will be shared with multiple pipelines or not.
     * </p>
     *
     * If {@link #isSharable()} is true then on {@link #handlerAdded(ChannelHandlerContext)} call,
     * a new {@link Writer} will create, and it will be mapped using {@link Channel#attr(AttributeKey)}
     * so {@link BrotliEncoder} can be shared with multiple pipelines. This works fine but there on every
     * {@link #encode(ChannelHandlerContext, ByteBuf, ByteBuf)} call, we have to get the {@link Writer} associated
     * with the appropriate channel. And this will add a overhead. So it is recommended to set {@link #isSharable()}
     * to {@code false} and create new {@link BrotliEncoder} instance for every pipeline.
     *
     * @param parameters {@link Encoder.Parameters} to use
     * @param isSharable Set to {@code true} if this instance is shared else set to {@code false}
     */
    public BrotliEncoder(Encoder.Parameters parameters, boolean isSharable) {
        super(ByteBuf.class);
        this.parameters = ObjectUtil.checkNotNull(parameters, "Parameters");
        this.isSharable = isSharable;
    }

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Writer writer = new Writer(parameters, ctx);
        if (isSharable) {
            ctx.channel().attr(ATTR).set(writer);
        } else {
            this.writer = writer;
        }
        super.handlerAdded(ctx);
    }

    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        finish(ctx);
        super.handlerRemoved(ctx);
    }

    @Override
    protected void encode(ChannelHandlerContext ctx, ByteBuf msg, ByteBuf out) throws Exception {
        // NO-OP
    }