Spring Cloud Stream 高级特性使用详解

# 默认重试次数为3，配置大于1时才会生效
spring.cloud.stream.bindings.<channelName>.consumer.maxAttempte=3 

    public static final String ERROR_CHANNEL_BEAN_NAME = "errorChannel"
    private SubscribableChannel registerErrorInfrastructure(
            ProducerDestination destination) {
        // destination.getName() + ".errors"
        String errorChannelName = errorsBaseName(destination);
        SubscribableChannel errorChannel;
        if (getApplicationContext().containsBean(errorChannelName)) {
            Object errorChannelObject = getApplicationContext().getBean(errorChannelName);
            if (!(errorChannelObject instanceof SubscribableChannel)) {
                throw new IllegalStateException("Error channel '" + errorChannelName
                        + "' must be a SubscribableChannel");
            }
            errorChannel = (SubscribableChannel) errorChannelObject;
        }
        else {
            errorChannel = new PublishSubscribeChannel();
            ((GenericApplicationContext) getApplicationContext()).registerBean(
                    errorChannelName, SubscribableChannel.class, () -> errorChannel);
        }
        MessageChannel defaultErrorChannel = null;
        if (getApplicationContext()
                .containsBean(IntegrationContextUtils.ERROR_CHANNEL_BEAN_NAME)) {
            defaultErrorChannel = getApplicationContext().getBean(
                    IntegrationContextUtils.ERROR_CHANNEL_BEAN_NAME,
                    MessageChannel.class);
        }
        if (defaultErrorChannel != null) {
            BridgeHandler errorBridge = new BridgeHandler();
            errorBridge.setOutputChannel(defaultErrorChannel);
            errorChannel.subscribe(errorBridge);
            String errorBridgeHandlerName = getErrorBridgeName(destination);
            ((GenericApplicationContext) getApplicationContext()).registerBean(
                    errorBridgeHandlerName, BridgeHandler.class, () -> errorBridge);
        }
        return errorChannel;
    }

spring.cloud.stream.bindings.output.destination=test-output
# 消息发送失败的处理逻辑默认是关闭的
spring.cloud.stream.bindings.output.producer.errorChannelEnabled=true

    @Bean("test-output.errors")
    MessageChannel testOutputErrorChannel() {
        return new PublishSubscribeChannel();
    }
    @Service
    class ErrorProduceService {
        @ServiceActivator(inputChannel = "test-output.errors")
        public void receiveProduceError(Message receiveMsg) {
            System.out.println("receive error msg: " + receiveMsg);
        }
    }

spring.cloud.stream.bindings.input.destination=test-input
spring.cloud.stream.bindings.input.group=test-input-group

@StreamListener(Sink.INPUT)
public void receive(String receiveMsg) {
    throw new RuntimeException("Oops");
}
@ServiceActivator(inputChannel = "test-input.test-input-group.errors")
public void receiveConsumeError(Message receiveMsg) {
    System.out.println("receive error msg: " + receiveMsg);
}

@Endpoint(id = "bindings")
public class BindingsEndpoint {
  ...
  @WriteOperation
    public void changeState(@Selector String name, State state) {
        Binding<?> binding = BindingsEndpoint.this.locateBinding(name);
        if (binding != null) {
            switch (state) {
            case STARTED:
                binding.start();
                break;
            case STOPPED:
                binding.stop();
                break;
            case PAUSED:
                binding.pause();
                break;
            case RESUMED:
                binding.resume();
                break;
            default:
                break;
            }
        }
    }
    @ReadOperation
    public List<?> queryStates() {
        List<Binding<?>> bindings = new ArrayList<>(gatherInputBindings());
        bindings.addAll(gatherOutputBindings());
        return this.objectMapper.convertValue(bindings, List.class);
    }
    @ReadOperation
    public Binding<?> queryState(@Selector String name) {
        Assert.notNull(name, "'name' must not be null");
        return this.locateBinding(name);
    }
  ...
}

  @Bean
  public Function<String, String> uppercase() {
      return x -> x.toUpperCase();
  }
  @Bean
  public Function<String, String> addprefix() {
      return x -> "prefix-" + x;
  }

public final class PartitioningInterceptor implements ChannelInterceptor {
      ...
      @Override
      public Message<?> preSend(Message<?> message, MessageChannel channel) {
      if (!message.getHeaders().containsKey(BinderHeaders.PARTITION_OVERRIDE)) {
        int partition = this.partitionHandler.determinePartition(message);
        return MessageConverterConfigurer.this.messageBuilderFactory
          .fromMessage(message)
          .setHeader(BinderHeaders.PARTITION_HEADER, partition).build();
      }
      else {
        return MessageConverterConfigurer.this.messageBuilderFactory
          .fromMessage(message)
          .setHeader(BinderHeaders.PARTITION_HEADER,
                     message.getHeaders()
                     .get(BinderHeaders.PARTITION_OVERRIDE))
          .removeHeader(BinderHeaders.PARTITION_OVERRIDE).build();
      }
    }
}
public class PartitionHandler {
      ...
      public int determinePartition(Message<?> message) {
        Object key = extractKey(message);
        int partition;
        if (this.producerProperties.getPartitionSelectorExpression() != null) {
            partition = this.producerProperties.getPartitionSelectorExpression()
                    .getValue(this.evaluationContext, key, Integer.class);
        }
        else {
            partition = this.partitionSelectorStrategy.selectPartition(key,
                    this.partitionCount);
        }
        // protection in case a user selector returns a negative.
        return Math.abs(partition % this.partitionCount);
    }
    private Object extractKey(Message<?> message) {
        Object key = invokeKeyExtractor(message);
        if (key == null && this.producerProperties.getPartitionKeyExpression() != null) {
            key = this.producerProperties.getPartitionKeyExpression()
                    .getValue(this.evaluationContext, message);
        }
        Assert.notNull(key, "Partition key cannot be null");
        return key;
    }
      ...
}

public interface PollableSink {
    /**
     * Input channel name.
     */
    String INPUT = "input";
    /**
     * @return input channel.
     */
    @Input(Sink.INPUT)
    PollableMessageSource input();
}