无法在 Spring 集成中将回复通道设置为消息头

Question

肯定有一些我一定错过的东西，所以在这里寻求帮助。

我正在使用 Spring Integration 和以下 HTTP 入站网关构建一个简单的 REST 应用程序：

<!-- Gateway -->
    <int-http:inbound-gateway id="fruitQuotePOSTGateway"
                              request-channel="fruitQuotePOSTRequests"
                              supported-methods="POST"
                              path="/api/v1/fruit-quote"
                              request-payload-type="java.lang.String"
                              reply-timeout="10000"
                              reply-channel="fruitQuotePOSTResponses"
                              error-channel="applicationErrors">
        <int-http:request-mapping consumes="application/xml" produces="application/xml"/>
    </int-http:inbound-gateway>

一旦一个 XML 进入这个网关，它会经历以下简单的步骤：

• 转换以生成与传入请求对应的 JAXB 对象
• 从 JAXB 对象读取“uuid”并将其设置为 SI（Spring 集成）消息的标头的消息标头丰富
• 转换以生成对调用客户端的 XML 响应。

首先，这是整个应用程序的 XML 配置（为简洁起见，省略了 HTTP 命名空间）：

<!-- Gateway -->
    <int-http:inbound-gateway id="fruitQuotePOSTGateway"
                              request-channel="fruitQuotePOSTRequests"
                              supported-methods="POST"
                              path="/api/v1/fruit-quote"
                              request-payload-type="java.lang.String"
                              reply-timeout="10000"
                              reply-channel="fruitQuotePOSTResponses"
                              error-channel="applicationErrors">
        <int-http:request-mapping consumes="application/xml" produces="application/xml"/>
    </int-http:inbound-gateway>

    <!--
    - Generate fruit quote request JAXB from the incoming request
    - Create a header "requestUUID" by reading it from fruit quote request JAXB
    - Generate fruit quote acknowledgement response for the calling client
    -->

    <int:transformer input-channel="fruitQuotePOSTRequests"
               ref="fruitQuoteTransformation"
               method="generateFruitQuoteRequestJAXB"/>

    <int:header-enricher input-channel="requestUUIDEnrichment" output-channel="orderIDGeneration">
        <int:header name="requestUUID" expression="payload.getFruitQuoteRequestJAXB().getFRUITQUOTEREQUESTDATA().getUuid()"/>
    </int:header-enricher>

    <int:transformer input-channel="fruitQuoteAcknowledgementGeneration"
                     ref="fruitQuoteTransformation"
                     method="generateFruitQuoteAcknowledgement"
                     output-channel="fruitQuotePOSTResponses"/>

    <!-- Error handling -->
    <int:transformer input-channel="applicationErrors"
                     ref="fruitQuoteTransformation"
                     method="generateFruitQuoteAcknowledgementWithError"
                     output-channel="fruitQuotePOSTResponses"/>

    <!-- Channels -->
    <int:channel id="fruitQuotePOSTRequests"/>
    <int:channel id="requestUUIDEnrichment"/>
    <int:channel id="fruitQuotePOSTResponses"/>
    <int:channel id="fruitQuoteAcknowledgementGeneration"/>
    <int:channel id="applicationErrors"/>

应用程序中从一个步骤流向另一个步骤的payload是一个自定义的Builder Object，如下（省略包名）：

import static java.util.Objects.nonNull;

public class FruiteQuoteComposite {
    private final FRUITQUOTEREQUEST fruitQuoteRequestJAXB;
    private final FruitQuoteApplicationException fruitQuoteApplicationException;
    private final Integer orderID;
    private final ErrorInformation errorInformation;

    private FruiteQuoteComposite(FruiteQuoteCompositeBuilder fruiteQuoteCompositeBuilder) {
        this.fruitQuoteRequestJAXB = fruiteQuoteCompositeBuilder.fruitQuoteRequestJAXB;
        this.fruitQuoteApplicationException = fruiteQuoteCompositeBuilder.fruitQuoteApplicationException;
        this.orderID = fruiteQuoteCompositeBuilder.orderID;
        this.errorInformation = fruiteQuoteCompositeBuilder.errorInformation;
    }

    public FruitQuoteApplicationException getFruitQuoteApplicationException() {
        return fruitQuoteApplicationException;
    }

    public FRUITQUOTEREQUEST getFruitQuoteRequestJAXB() {
        return fruitQuoteRequestJAXB;
    }

    public Integer getOrderID() {
        return orderID;
    }

    public ErrorInformation getErrorInformation() {
        return errorInformation;
    }

    public static class FruiteQuoteCompositeBuilder {
        private FRUITQUOTEREQUEST fruitQuoteRequestJAXB;
        private FruitQuoteApplicationException fruitQuoteApplicationException;
        private Integer orderID;
        private ErrorInformation errorInformation;

        public FruiteQuoteCompositeBuilder() {
        }

        public FruiteQuoteCompositeBuilder setFruitQuoteRequestJAXB(FRUITQUOTEREQUEST fruitQuoteRequestJAXB) {
            if (nonNull(fruitQuoteRequestJAXB)) {
                this.fruitQuoteRequestJAXB = fruitQuoteRequestJAXB;
            }

            return this;
        }

        public FruiteQuoteCompositeBuilder setFruitQuoteApplicationException(FruitQuoteApplicationException fruitQuoteApplicationException) {
            if (nonNull(fruitQuoteApplicationException)) {
                this.fruitQuoteApplicationException = fruitQuoteApplicationException;
            }

            return this;
        }

        public FruiteQuoteCompositeBuilder setOrderID(Integer orderID) {
            if(nonNull(orderID)) {
                this.orderID = orderID;
            }

            return this;
        }

        public FruiteQuoteCompositeBuilder setErrorInformation(ErrorInformation errorInformation) {
            if (nonNull( errorInformation )) {
                this.errorInformation = errorInformation;
            }
            return this;
        }

        public FruiteQuoteComposite build() {
            return new FruiteQuoteComposite(this);
        }
    }
}

我没有在转换器上使用“输出通道”的原因是因为我想在运行转换的 java 逻辑中明确选择 replyChannel/outgoing 路由。

例如，在 FruitQuoteTransformation.generateFruitQuoteRequestJAXB 方法中，我设置了一条成功路径和另一条异常/错误路径，如下所示：

public Message<FruiteQuoteComposite> generateFruitQuoteRequestJAXB(Message<String> fruitQuoteRequestMessage) {
        String fruitQuoteRequest = fruitQuoteRequestMessage.getPayload();
        Unmarshaller unmarshaller;
        FRUITQUOTEREQUEST fruitQuoteRequestJAXB;

        try {
            unmarshaller = requireNonNull(fruitQuoteRequestJaxbContext).createUnmarshaller();
            fruitQuoteRequestJAXB = (FRUITQUOTEREQUEST) requireNonNull(unmarshaller)
                    .unmarshal(new StringReader(fruitQuoteRequest));
        } catch (JAXBException jaxbException) {
            logger.error("JAXB Unmarshalling exception occurred with error code :: " + ERR_FRUIT_QUOTE_REQUEST_JAXB_TRANSFORMATION, jaxbException);
            FruitQuoteApplicationException fruitQuoteApplicationException = generateFruitQuoteApplicationException(ERR_FRUIT_QUOTE_REQUEST_JAXB_TRANSFORMATION, MESSAGE_FRUIT_QUOTE_INTERNAL_SYSTEM_ERROR);

            FruiteQuoteComposite outboundFruitQuoteComposite = new FruiteQuoteComposite.FruiteQuoteCompositeBuilder()
                    .setFruitQuoteApplicationException(fruitQuoteApplicationException)
                    .build();

            return withPayload(requireNonNull(outboundFruitQuoteComposite))
                    .setHeader(MessageHeaders.REPLY_CHANNEL, "applicationErrors")
                    .build();
        }

        FruiteQuoteComposite outboundFruitQuoteComposite = new FruiteQuoteComposite.FruiteQuoteCompositeBuilder()
                .setFruitQuoteRequestJAXB(fruitQuoteRequestJAXB)
                .build();

        return withPayload(requireNonNull(outboundFruitQuoteComposite))
                .setHeader(MessageHeaders.REPLY_CHANNEL, "requestUUIDEnrichment")
                .build();
    }

• 我的第一个问题 出于某种原因，.setHeader 调用没有按预期工作，并且消息不会发送到下一个频道。有什么我想念的吗？即使我使用 .setReplyChannelName，结果也是一样的。
• 我的第二个问题 如果问题 1) 有解决方案，将整体 SI 配置保持为基于 XML，是否有另一种方法来设置自定义回复通道？我想到的唯一选择是在每个变压器之后使用路由器，但这似乎太冗长了。

你能帮忙吗？

Answer 1

你绝不能乱用框架的replyChannel 标头；它不用于路由目的。

replyChannel 是一个内部通道，对于用于关联对请求的回复的每条消息都是唯一的。在入站网关上通常不需要显式的reply-channel；如果这样做，它只是在运行时桥接到消息的 replyChannel 标头。

应该在网关的error-channel 上处理错误情况，而不是通过抛出异常来处理。不同的异常类型可以指示不同的错误。