Spring-Integration：在异常时不发送Tcp服务器响应

我将旧的tcp服务器代码迁移到spring-boot并添加了spring-integration（基于注释）依赖项来处理tcp套接字连接。

我的入站通道是tcpIn（），出站通道是serviceChannel（），我创建了一个自定义通道[exceptionEventChannel（）]来保存异常事件消息。

我有一个自定义序列化器/ Deserialier方法（ByteArrayLengthPrefixSerializer（）扩展AbstractPooledBufferByteArraySerializer），以及一个MessageHandler @ServiceActivator方法将响应发送回tcp客户端。

//SpringBoot 2.0.3.RELEASE, Spring Integration 5.0.6.RELEASE

package com.test.config;


import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.event.EventListener;
import org.springframework.integration.annotation.IntegrationComponentScan;
import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.integration.annotation.Transformer;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.event.inbound.ApplicationEventListeningMessageProducer;
import org.springframework.integration.ip.IpHeaders;
import org.springframework.integration.ip.tcp.TcpReceivingChannelAdapter;
import org.springframework.integration.ip.tcp.TcpSendingMessageHandler;
import org.springframework.integration.ip.tcp.connection.*;
import org.springframework.integration.ip.tcp.serializer.TcpDeserializationExceptionEvent;
import org.springframework.integration.router.ErrorMessageExceptionTypeRouter;
import org.springframework.integration.support.MessageBuilder;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.MessageHandlingException;
import org.springframework.messaging.MessagingException;

import java.io.IOException;

@Configuration
@IntegrationComponentScan
public class TcpConfiguration {
    @SuppressWarnings("unused")
    @Value("${tcp.connection.port}")
    private int tcpPort;

    @Bean
    TcpConnectionEventListener customerTcpListener() {
        return new TcpConnectionEventListener();
    }

    @Bean
    public MessageChannel tcpIn() {
        return new DirectChannel();
    }

    @Bean
    public MessageChannel serviceChannel() {
        return new DirectChannel();
    }

    @ConditionalOnMissingBean(name = "errorChannel")
    @Bean
    public MessageChannel errorChannel() {
        return new DirectChannel();
    }

    @Bean
    public MessageChannel exceptionEventChannel() {
        return new DirectChannel();
    }

    @Bean
    public ByteArrayLengthPrefixSerializer byteArrayLengthPrefixSerializer() {
        ByteArrayLengthPrefixSerializer byteArrayLengthPrefixSerializer = new ByteArrayLengthPrefixSerializer();
        byteArrayLengthPrefixSerializer.setMaxMessageSize(98304); //max allowed size set to 96kb
        return byteArrayLengthPrefixSerializer;
    }

    @Bean
    public AbstractServerConnectionFactory tcpNetServerConnectionFactory() {
        TcpNetServerConnectionFactory tcpServerCf = new TcpNetServerConnectionFactory(tcpPort);
        tcpServerCf.setSerializer(byteArrayLengthPrefixSerializer());
        tcpServerCf.setDeserializer(byteArrayLengthPrefixSerializer());
        return tcpServerCf;

    }

    @Bean
    public TcpReceivingChannelAdapter tcpReceivingChannelAdapter() {
        TcpReceivingChannelAdapter adapter = new TcpReceivingChannelAdapter();
        adapter.setConnectionFactory(tcpNetServerConnectionFactory());
        adapter.setOutputChannel(tcpIn());
        adapter.setErrorChannel(exceptionEventChannel());
        return adapter;
    }

    @ServiceActivator(inputChannel = "exceptionEventChannel", outputChannel = "serviceChannel")
    public String handle(Message<MessagingException> msg) {
        //String unfilteredMessage = new String(byteMessage, StandardCharsets.US_ASCII);
        System.out.println("-----------------EXCEPTION ==> " + msg);
        return msg.toString();
    }

    @Transformer(inputChannel = "errorChannel", outputChannel = "serviceChannel")
    public String transformer(String msg) {
        //String unfilteredMessage = new String(byteMessage, StandardCharsets.US_ASCII);
        System.out.println("-----------------ERROR ==> " + msg);
        return msg.toString();
    }


    @ServiceActivator(inputChannel = "serviceChannel")
    @Bean
    public TcpSendingMessageHandler out(AbstractServerConnectionFactory cf) {
        TcpSendingMessageHandler tcpSendingMessageHandler = new TcpSendingMessageHandler();
        tcpSendingMessageHandler.setConnectionFactory(cf);
        return tcpSendingMessageHandler;
    }


    @Bean
    public ApplicationListener<TcpDeserializationExceptionEvent> listener() {
        return new ApplicationListener<TcpDeserializationExceptionEvent>() {

            @Override
            public void onApplicationEvent(TcpDeserializationExceptionEvent tcpDeserializationExceptionEvent) {
                exceptionEventChannel().send(MessageBuilder.withPayload(tcpDeserializationExceptionEvent.getCause())
                        .build());
            }

        };
    }
}

tcpIn（）中的消息被发送到单独的@Component类中的@ServiceActivator方法，其结构如下：

@Component
public class TcpServiceActivator {

    @Autowired
    public TcpServiceActivator() {
    }


    @ServiceActivator(inputChannel = "tcpIn", outputChannel = "serviceChannel")
    public String service(byte[] byteMessage) {
     // Business Logic returns String Ack Response
    }

我没有运行成功方案的问题。我的Tcp TestClient按预期获得Ack响应。

但是，当我尝试模拟异常时，比如Deserializer Exception，异常消息不会作为对Tcp Client的响应发回。我可以看到我的Application Listener获取TcpDeserializationExceptionEvent并将消息发送到exceptionEventChannel。 @ServiceActivator方法句柄（Message msg）也会打印我的异常消息。但它永远不会到达MessageHandler方法out（AbstractServerConnectionFactory cf）中的断点（在调试模式下）。

我很难理解什么是错的。在此先感谢您的帮助。

更新：我注意到在响应可以发送之前，Socket因异常而关闭。我正试图想办法解决这个问题

解决方案更新（2019年3月12日）：

由Gary提供，我编辑了我的反序列化器以返回一条消息，该消息可以通过@Router方法跟踪并重定向到errorChannel。监听errorchannel的ServiceActivator然后将所需的错误消息发送到outputChannel。这个解决方案似乎有效。

我的反序列化方法在ByteArrayLengthPrefixSerializer中返回一个“特殊值”作为Gary推荐，而不是原始的inputStream消息。

    public byte[] doDeserialize(InputStream inputStream, byte[] buffer) throws IOException {
        boolean isValidMessage = false;
        try {
            int messageLength = this.readPrefix(inputStream);
            if (messageLength > 0 && fillUntilMaxDeterminedSize(inputStream, buffer, messageLength)) {
                return this.copyToSizedArray(buffer, messageLength);
            }
            return EventType.MSG_INVALID.getName().getBytes(); 
        } catch (SoftEndOfStreamException eose) {
            return EventType.MSG_INVALID.getName().getBytes();
        }
    }

我还制作了一些新的频道来容纳我的路由器，以便流程如下：

成功流程tcpIn（@Router） - > serviceChannel（包含业务逻辑的@serviceActivator） - > outputChannel（向客户端发送响应的@serviceActivator）

异常流tcpIn（@Router） - > errorChannel（准备错误响应消息的@serviceActivator） - > outputChannel（向客户端发送响应的@serviceActivator）

我的@Router和'errorHandling'@serviceActivator -

    @Router(inputChannel = "tcpIn", defaultOutputChannel = "errorChannel")
    public String messageRouter(byte[] byteMessage) {
        String unfilteredMessage = new String(byteMessage, StandardCharsets.US_ASCII);
        System.out.println("------------------> "+unfilteredMessage);
        if (Arrays.equals(EventType.MSG_INVALID.getName().getBytes(), byteMessage)) {
            return "errorChannel";
        }
        return "serviceChannel";
    }


    @ServiceActivator(inputChannel = "errorChannel", outputChannel = "outputChannel")
    public String errorHandler(byte[] byteMessage) {
        return Message.ACK_RETRY;
    }