HTTP/2 Server Library

<dependency>
  <groupId>org.eclipse.jetty.http2</groupId>
  <artifactId>jetty-http2-server</artifactId>
  <version>12.0.16-SNAPSHOT</version>
</dependency>

// Create a Server instance.
Server server = new Server();

ServerSessionListener sessionListener = new ServerSessionListener() {};

// Create a ServerConnector with RawHTTP2ServerConnectionFactory.
RawHTTP2ServerConnectionFactory http2 = new RawHTTP2ServerConnectionFactory(sessionListener);

// Configure RawHTTP2ServerConnectionFactory, for example:

// Configure the max number of concurrent requests.
http2.setMaxConcurrentStreams(128);
// Enable support for CONNECT.
http2.setConnectProtocolEnabled(true);

// Create the ServerConnector.
ServerConnector connector = new ServerConnector(server, http2);

// Add the Connector to the Server
server.addConnector(connector);

// Start the Server so it starts accepting connections from clients.
server.start();

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public void onAccept(Session session)
    {
        SocketAddress remoteAddress = session.getRemoteSocketAddress();
        System.getLogger("http2").log(INFO, "Connection from {0}", remoteAddress);
    }
};

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public Map<Integer, Integer> onPreface(Session session)
    {
        // Customize the settings, for example:
        Map<Integer, Integer> settings = new HashMap<>();

        // Tell the client that HTTP/2 push is disabled.
        settings.put(SettingsFrame.ENABLE_PUSH, 0);

        return settings;
    }
};

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
    {
        // This is the "new stream" event, so it's guaranteed to be a request.
        MetaData.Request request = (MetaData.Request)frame.getMetaData();

        // Return a Stream.Listener to handle the request events,
        // for example request content events or a request reset.
        return new Stream.Listener()
        {
            // Override callback methods for events you are interested in.
        };
    }
};

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
    {
        MetaData.Request request = (MetaData.Request)frame.getMetaData();

        // Demand for request data content.
        stream.demand();

        // Return a Stream.Listener to handle the request events.
        return new Stream.Listener()
        {
            @Override
            public void onDataAvailable(Stream stream)
            {
                Stream.Data data = stream.readData();

                if (data == null)
                {
                    stream.demand();
                    return;
                }

                // Get the content buffer.
                ByteBuffer buffer = data.frame().getByteBuffer();

                // Consume the buffer, here - as an example - just log it.
                System.getLogger("http2").log(INFO, "Consuming buffer {0}", buffer);

                // Tell the implementation that the buffer has been consumed.
                data.release();

                if (!data.frame().isEndStream())
                {
                    // Demand more DATA frames when they are available.
                    stream.demand();
                }
            }
        };
    }
};

record Chunk(ByteBuffer byteBuffer, Callback callback)
{
}

// A queue that consumers poll to consume content asynchronously.
Queue<Chunk> dataQueue = new ConcurrentLinkedQueue<>();

// Implementation of Stream.Listener.onDataAvailable(Stream stream)
// in case of unwrapping of the Data object for asynchronous content
// consumption and demand.
Stream.Listener listener = new Stream.Listener()
{
    @Override
    public void onDataAvailable(Stream stream)
    {
        Stream.Data data = stream.readData();

        if (data == null)
        {
            stream.demand();
            return;
        }

        // Get the content buffer.
        ByteBuffer byteBuffer = data.frame().getByteBuffer();

        // Unwrap the Data object, converting it to a Chunk.
        // The Data.release() semantic is maintained in the completion of the Callback.
        dataQueue.offer(new Chunk(byteBuffer, Callback.from(() ->
        {
            // When the buffer has been consumed, then:
            // A) release the Data object.
            data.release();
            // B) possibly demand more DATA frames.
            if (!data.frame().isEndStream())
                stream.demand();
        })));

        // Do not demand more data here, to avoid to overflow the queue.
    }
};

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
    {
        // Send a response after reading the request.
        MetaData.Request request = (MetaData.Request)frame.getMetaData();
        if (frame.isEndStream())
        {
            respond(stream, request);
            return null;
        }
        else
        {
            // Demand for request data.
            stream.demand();

            // Return a listener to handle the request events.
            return new Stream.Listener()
            {
                @Override
                public void onDataAvailable(Stream stream)
                {
                    Stream.Data data = stream.readData();

                    if (data == null)
                    {
                        stream.demand();
                        return;
                    }

                    // Consume the request content.
                    data.release();

                    if (data.frame().isEndStream())
                        respond(stream, request);
                    else
                        stream.demand();
                }
            };
        }
    }

    private void respond(Stream stream, MetaData.Request request)
    {
        // Prepare the response HEADERS frame.

        // The response HTTP status and HTTP headers.
        MetaData.Response response = new MetaData.Response(HttpStatus.OK_200, null, HttpVersion.HTTP_2, HttpFields.EMPTY);

        if (HttpMethod.GET.is(request.getMethod()))
        {
            // The response content.
            ByteBuffer resourceBytes = getResourceBytes(request);

            // Send the HEADERS frame with the response status and headers,
            // and a DATA frame with the response content bytes.
            stream.headers(new HeadersFrame(stream.getId(), response, null, false))
                .thenCompose(s -> s.data(new DataFrame(s.getId(), resourceBytes, true)));
        }
        else
        {
            // Send just the HEADERS frame with the response status and headers.
            stream.headers(new HeadersFrame(stream.getId(), response, null, true));
        }
    }
};

ServerSessionListener sessionListener = new ServerSessionListener()
{
    @Override
    public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
    {
        float requestRate = calculateRequestRate();

        if (requestRate > maxRequestRate)
        {
            stream.reset(new ResetFrame(stream.getId(), ErrorCode.REFUSED_STREAM_ERROR.code), Callback.NOOP);
            return null;
        }
        else
        {
            // The request is accepted.
            MetaData.Request request = (MetaData.Request)frame.getMetaData();
            // Return a Stream.Listener to handle the request events.
            return new Stream.Listener()
            {
                // Override callback methods for events you are interested in.
            };
        }
    }
};

// The favicon bytes.
ByteBuffer faviconBuffer = BufferUtil.toBuffer(ResourceFactory.root().newResource("/path/to/favicon.ico"), true);

ServerSessionListener sessionListener = new ServerSessionListener()
{
    // By default, push is enabled.
    private boolean pushEnabled = true;

    @Override
    public void onSettings(Session session, SettingsFrame frame)
    {
        // Check whether the client sent an ENABLE_PUSH setting.
        Map<Integer, Integer> settings = frame.getSettings();
        Integer enablePush = settings.get(SettingsFrame.ENABLE_PUSH);
        if (enablePush != null)
            pushEnabled = enablePush == 1;
    }

    @Override
    public Stream.Listener onNewStream(Stream stream, HeadersFrame frame)
    {
        MetaData.Request request = (MetaData.Request)frame.getMetaData();
        if (pushEnabled && request.getHttpURI().toString().endsWith("/index.html"))
        {
            // Push the favicon.
            HttpURI pushedURI = HttpURI.build(request.getHttpURI()).path("/favicon.ico");
            MetaData.Request pushedRequest = new MetaData.Request("GET", pushedURI, HttpVersion.HTTP_2, HttpFields.EMPTY);
            PushPromiseFrame promiseFrame = new PushPromiseFrame(stream.getId(), 0, pushedRequest);
            stream.push(promiseFrame, null)
                .thenCompose(pushedStream ->
                {
                    // Send the favicon "response".
                    MetaData.Response pushedResponse = new MetaData.Response(HttpStatus.OK_200, null, HttpVersion.HTTP_2, HttpFields.EMPTY);
                    return pushedStream.headers(new HeadersFrame(pushedStream.getId(), pushedResponse, null, false))
                        .thenCompose(pushed -> pushed.data(new DataFrame(pushed.getId(), faviconBuffer.slice(), true)));
                });
        }
        // Return a Stream.Listener to handle the request events.
        return new Stream.Listener()
        {
            // Override callback methods for events you are interested in.
        };
    }
};