如何使用spring集成在TCP连接上实现保活连接？

我有一个使用 spring 集成 TCP 构建的 TCP 客户端，服务器支持保持活动消息（ping/pong 风格）。连接是使用配置的CachingClientConnectionFactory我想利用这个服务器功能。这是我的 bean 配置：

private static final int SERIALIZER_HEADER_SIZE = 2;

/**
 * Serializer used by connection factory to send and receive messages
 */
@Bean
public ByteArrayLengthHeaderSerializer byteArrayLengthHeaderSerializer() {
    return new ByteArrayLengthHeaderSerializer(SERIALIZER_HEADER_SIZE);
}

@Bean
public AbstractClientConnectionFactory tcpClientConnectionFactory() {
    TcpNetClientConnectionFactory connFactory =
        new TcpNetClientConnectionFactory(props.getUrl(), props.getPort());
    connFactory.setSerializer(byteArrayLengthHeaderSerializer());
    connFactory.setDeserializer(byteArrayLengthHeaderSerializer());
    connFactory.setSoTimeout(props.getSoTimeout());
    if (props.isUseSSL()) {
        connFactory.setTcpSocketFactorySupport(new DefaultTcpNetSSLSocketFactorySupport(() -> {
            return SSLContext.getDefault();
        }));
    }

    return connFactory;
}

/**
 * Connection factory used to create TCP client socket connections
 */
@Bean
public AbstractClientConnectionFactory tcpCachedClientConnectionFactory() {
    CachingClientConnectionFactory cachingConnFactory =
        new CachingClientConnectionFactory(tcpClientConnectionFactory(), props.getMaxPoolSize());
    cachingConnFactory.setConnectionWaitTimeout(props.getMaxPoolWait());
    return cachingConnFactory;
}

使用此处发布的解决方案配置保持活动以保持连接始终处于活动状态 https://stackoverflow.com/questions/46583757/configure-keep-alive-to-keep-connection-alive-all-the-time我可以保持连接打开，但我也想利用这些服务器保持活动消息并不时发送这些消息来检查连接是否仍然活动。这可以提高客户端的性能，因为如果套接字关闭，则不需要重新连接/创建新连接。

基于此，有人对如何使用 spring 集成来实现这一点有建议吗？

当使用简单的客户端连接工厂时，使用以下命令设置应用程序级心跳消息非常容易@InboundChannelAdapter.

简单的例子：

@SpringBootApplication
public class So46918267Application {

    public static void main(String[] args) throws IOException {
        // Simulated Server
        final ServerSocket server = ServerSocketFactory.getDefault().createServerSocket(1234);
        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.execute(() -> {
            try {
                Socket socket = server.accept();
                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String line;
                while ((line = reader.readLine()) != null) {
                    System.out.println(line);
                    if (line.equals("keep_alive")) {
                        socket.getOutputStream().write("OK\r\n".getBytes());
                    }
                }
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        });
        ConfigurableApplicationContext context = SpringApplication.run(So46918267Application.class, args);
        System.out.println("Hit enter to terminate");
        System.in.read();
        executor.shutdownNow();
        context.close();
        server.close();
    }

    @Bean
    public TcpNetClientConnectionFactory client() {
        return new TcpNetClientConnectionFactory("localhost", 1234);
    }

    @ServiceActivator(inputChannel = "toTcp")
    @Bean
    public TcpOutboundGateway gateway() {
        TcpOutboundGateway gateway = new TcpOutboundGateway();
        gateway.setConnectionFactory(client());
        return gateway;
    }

    // HEARTBEATS

    private final Message<?> heartbeatMessage = MessageBuilder.withPayload("keep_alive")
            .setReplyChannelName("heartbeatReplies")
            .build();

    @InboundChannelAdapter(channel = "toTcp", poller = @Poller(fixedDelay = "25000"))
    public Message<?> heartbeat() {
        return this.heartbeatMessage;
    }

    @ServiceActivator(inputChannel = "heartbeatReplies")
    public void reply(byte[] reply) {
        System.out.println(new String(reply));
    }

}

当使用CachingClientConnectionFactory但是，尚不清楚为什么要保持空闲连接池打开。但是，池的工作方式是将空闲连接保留在队列中，因此每个请求都将转到最旧的连接，然后该连接将返回到队列的末尾。

Adding maxMessagesPerPoll会在每次轮询中发出该数量的消息并且......

@InboundChannelAdapter(channel = "toTcp", 
    poller = @Poller(fixedDelay = "25000", maxMessagesPerPoll = "5"))

将保持最多 5 个连接打开。它不会打开新连接（如果至少有一个），但如果池包含 5 个或更多连接，则至少有 5 个连接将保持打开状态。如果没有打开的连接，它将只打开一个。