public IOEventHandler createHandler()

in httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClientProtocolNegotiationStarter.java [107:271]
147 lines of code
27 McCabe index (conditional complexity)

    public IOEventHandler createHandler(final ProtocolIOSession ioSession, final Object attachment) {
        final ClientHttp1StreamDuplexerFactory http1StreamHandlerFactory;
        final ClientH2StreamMultiplexerFactory http2StreamHandlerFactory;

        if (STREAM_LOG.isDebugEnabled()
                || HEADER_LOG.isDebugEnabled()
                || FRAME_LOG.isDebugEnabled()
                || FRAME_PAYLOAD_LOG.isDebugEnabled()
                || FLOW_CTRL_LOG.isDebugEnabled()) {
            final String id = ioSession.getId();
            http1StreamHandlerFactory = new ClientHttp1StreamDuplexerFactory(
                    httpProcessor,
                    h1Config,
                    charCodingConfig,
                    http1ConnectionReuseStrategy,
                    http1ResponseParserFactory,
                    http1RequestWriterFactory,
                    new Http1StreamListener() {

                        @Override
                        public void onRequestHead(final HttpConnection connection, final HttpRequest request) {
                            if (HEADER_LOG.isDebugEnabled()) {
                                HEADER_LOG.debug("{} >> {}", id, new RequestLine(request));
                                for (final Iterator<Header> it = request.headerIterator(); it.hasNext(); ) {
                                    HEADER_LOG.debug("{} >> {}", id, it.next());
                                }
                            }
                        }

                        @Override
                        public void onResponseHead(final HttpConnection connection, final HttpResponse response) {
                            if (HEADER_LOG.isDebugEnabled()) {
                                HEADER_LOG.debug("{} << {}", id, new StatusLine(response));
                                for (final Iterator<Header> it = response.headerIterator(); it.hasNext(); ) {
                                    HEADER_LOG.debug("{} << {}", id, it.next());
                                }
                            }
                        }

                        @Override
                        public void onExchangeComplete(final HttpConnection connection, final boolean keepAlive) {
                            if (STREAM_LOG.isDebugEnabled()) {
                                if (keepAlive) {
                                    STREAM_LOG.debug("{} Connection is kept alive", id);
                                } else {
                                    STREAM_LOG.debug("{} Connection is not kept alive", id);
                                }
                            }
                        }

                    });
            http2StreamHandlerFactory = new ClientH2StreamMultiplexerFactory(
                    httpProcessor,
                    exchangeHandlerFactory,
                    h2Config,
                    charCodingConfig,
                    new H2StreamListener() {

                        final FramePrinter framePrinter = new FramePrinter();

                        private void logFrameInfo(final String prefix, final RawFrame frame) {
                            try {
                                final LogAppendable logAppendable = new LogAppendable(FRAME_LOG, prefix);
                                framePrinter.printFrameInfo(frame, logAppendable);
                                logAppendable.flush();
                            } catch (final IOException ignore) {
                            }
                        }

                        private void logFramePayload(final String prefix, final RawFrame frame) {
                            try {
                                final LogAppendable logAppendable = new LogAppendable(FRAME_PAYLOAD_LOG, prefix);
                                framePrinter.printPayload(frame, logAppendable);
                                logAppendable.flush();
                            } catch (final IOException ignore) {
                            }
                        }

                        private void logFlowControl(final String prefix, final int streamId, final int delta, final int actualSize) {
                            FLOW_CTRL_LOG.debug("{} stream {} flow control {} -> {}", prefix, streamId, delta, actualSize);
                        }

                        @Override
                        public void onHeaderInput(final HttpConnection connection, final int streamId, final List<? extends Header> headers) {
                            if (HEADER_LOG.isDebugEnabled()) {
                                for (int i = 0; i < headers.size(); i++) {
                                    HEADER_LOG.debug("{} << {}", id, headers.get(i));
                                }
                            }
                        }

                        @Override
                        public void onHeaderOutput(final HttpConnection connection, final int streamId, final List<? extends Header> headers) {
                            if (HEADER_LOG.isDebugEnabled()) {
                                for (int i = 0; i < headers.size(); i++) {
                                    HEADER_LOG.debug("{} >> {}", id, headers.get(i));
                                }
                            }
                        }

                        @Override
                        public void onFrameInput(final HttpConnection connection, final int streamId, final RawFrame frame) {
                            if (FRAME_LOG.isDebugEnabled()) {
                                logFrameInfo(id + " <<", frame);
                            }
                            if (FRAME_PAYLOAD_LOG.isDebugEnabled()) {
                                logFramePayload(id + " <<", frame);
                            }
                        }

                        @Override
                        public void onFrameOutput(final HttpConnection connection, final int streamId, final RawFrame frame) {
                            if (FRAME_LOG.isDebugEnabled()) {
                                logFrameInfo(id + " >>", frame);
                            }
                            if (FRAME_PAYLOAD_LOG.isDebugEnabled()) {
                                logFramePayload(id + " >>", frame);
                            }
                        }

                        @Override
                        public void onInputFlowControl(final HttpConnection connection, final int streamId, final int delta, final int actualSize) {
                            if (FLOW_CTRL_LOG.isDebugEnabled()) {
                                logFlowControl(id + " <<", streamId, delta, actualSize);
                            }
                        }

                        @Override
                        public void onOutputFlowControl(final HttpConnection connection, final int streamId, final int delta, final int actualSize) {
                            if (FLOW_CTRL_LOG.isDebugEnabled()) {
                                logFlowControl(id + " >>", streamId, delta, actualSize);
                            }
                        }

                    });
        } else {
            http1StreamHandlerFactory = new ClientHttp1StreamDuplexerFactory(
                    httpProcessor,
                    h1Config,
                    charCodingConfig,
                    http1ConnectionReuseStrategy,
                    http1ResponseParserFactory,
                    http1RequestWriterFactory,
                    null);
            http2StreamHandlerFactory = new ClientH2StreamMultiplexerFactory(
                    httpProcessor,
                    exchangeHandlerFactory,
                    h2Config,
                    charCodingConfig,
                    null);
        }

        ioSession.registerProtocol(ApplicationProtocol.HTTP_1_1.id, new ClientHttp1UpgradeHandler(http1StreamHandlerFactory));
        ioSession.registerProtocol(ApplicationProtocol.HTTP_2.id, new ClientH2UpgradeHandler(http2StreamHandlerFactory));

        final HttpVersionPolicy versionPolicy = attachment instanceof HttpVersionPolicy ? (HttpVersionPolicy) attachment : HttpVersionPolicy.NEGOTIATE;
        switch (versionPolicy) {
            case FORCE_HTTP_2:
                return new ClientH2PrefaceHandler(ioSession, http2StreamHandlerFactory, false);
            case FORCE_HTTP_1:
                return new ClientHttp1IOEventHandler(http1StreamHandlerFactory.create(ioSession));
            default:
                return new HttpProtocolNegotiator(ioSession, null);
        }
   }