Http2ChannelDuplexHandler Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2ChannelDuplexHandler.java lines 34–92

public abstract class Http2ChannelDuplexHandler extends ChannelDuplexHandler {

    private volatile Http2FrameCodec frameCodec;

    @Override
    public final void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        frameCodec = requireHttp2FrameCodec(ctx);
        handlerAdded0(ctx);
    }

    protected void handlerAdded0(@SuppressWarnings("unused") ChannelHandlerContext ctx) throws Exception {
        // NOOP
    }

    @Override
    public final void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        try {
            handlerRemoved0(ctx);
        } finally {
            frameCodec = null;
        }
    }

    protected void handlerRemoved0(@SuppressWarnings("unused") ChannelHandlerContext ctx) throws Exception {
        // NOOP
    }

    /**
     * Creates a new {@link Http2FrameStream} object.
     *
     * <p>This method is <em>thread-safe</em>.
     */
    public final Http2FrameStream newStream() {
        Http2FrameCodec codec = frameCodec;
        if (codec == null) {
            throw new IllegalStateException(StringUtil.simpleClassName(Http2FrameCodec.class) + " not found." +
                    " Has the handler been added to a pipeline?");
        }
        return codec.newStream();
    }

    /**
     * Allows to iterate over all currently active streams.
     *
     * <p>This method may only be called from the eventloop thread.
     */
    protected final void forEachActiveStream(Http2FrameStreamVisitor streamVisitor) throws Http2Exception {
        frameCodec.forEachActiveStream(streamVisitor);
    }

    private static Http2FrameCodec requireHttp2FrameCodec(ChannelHandlerContext ctx) {
        ChannelHandlerContext frameCodecCtx = ctx.pipeline().context(Http2FrameCodec.class);
        if (frameCodecCtx == null) {
            throw new IllegalArgumentException(Http2FrameCodec.class.getSimpleName()
                                               + " was not found in the channel pipeline.");
        }
        return (Http2FrameCodec) frameCodecCtx.handler();
    }
}