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AMQP Message Headers

Overview

The Spring Integration AMQP Adapters automatically map all AMQP properties and headers. (This is a change from 4.3 - previously, only standard headers were mapped). By default, these properties are copied to and from Spring Integration MessageHeaders by using the DefaultAmqpHeaderMapper.

You can pass in your own implementation of AMQP-specific header mappers, as the adapters have properties to support doing so.

Any user-defined headers within the AMQP MessageProperties are copied to or from an AMQP message, unless explicitly negated by the requestHeaderNames or replyHeaderNames properties of the DefaultAmqpHeaderMapper. By default, for an outbound mapper, no x-* headers are mapped. See the caution that appears later in this section for why.

To override the default and revert to the pre-4.3 behavior, use STANDARD_REQUEST_HEADERS and STANDARD_REPLY_HEADERS in the properties.

When mapping user-defined headers, the values can also contain simple wildcard patterns (such as thing* or *thing) to be matched. The * matches all headers.

Starting with version 4.1, the AbstractHeaderMapper (a DefaultAmqpHeaderMapper superclass) lets the NON_STANDARD_HEADERS token be configured for the requestHeaderNames and replyHeaderNames properties (in addition to the existing STANDARD_REQUEST_HEADERS and STANDARD_REPLY_HEADERS) to map all user-defined headers.

The org.springframework.amqp.support.AmqpHeaders class identifies the default headers that are used by the DefaultAmqpHeaderMapper:

  • amqp_appId

  • amqp_clusterId

  • amqp_contentEncoding

  • amqp_contentLength

  • content-type (see The contentType Header)

  • amqp_correlationId

  • amqp_delay

  • amqp_deliveryMode

  • amqp_deliveryTag

  • amqp_expiration

  • amqp_messageCount

  • amqp_messageId

  • amqp_receivedDelay

  • amqp_receivedDeliveryMode

  • amqp_receivedExchange

  • amqp_receivedRoutingKey

  • amqp_redelivered

  • amqp_replyTo

  • amqp_timestamp

  • amqp_type

  • amqp_userId

  • amqp_publishConfirm

  • amqp_publishConfirmNackCause

  • amqp_returnReplyCode

  • amqp_returnReplyText

  • amqp_returnExchange

  • amqp_returnRoutingKey

  • amqp_channel

  • amqp_consumerTag

  • amqp_consumerQueue

As mentioned earlier in this section, using a header mapping pattern of * is a common way to copy all headers. However, this can have some unexpected side effects, because certain RabbitMQ proprietary properties/headers are also copied. For example, when you use federation, the received message may have a property named x-received-from, which contains the node that sent the message. If you use the wildcard character * for the request and reply header mapping on the inbound gateway, this header is copied, which may cause some issues with federation. This reply message may be federated back to the sending broker, which may think that a message is looping and, as a result, silently drop it. If you wish to use the convenience of wildcard header mapping, you may need to filter out some headers in the downstream flow. For example, to avoid copying the x-received-from header back to the reply you can use <int:header-filter …​ header-names="x-received-from"> before sending the reply to the AMQP inbound gateway. Alternatively, you can explicitly list those properties that you actually want mapped, instead of using wildcards. For these reasons, for inbound messages, the mapper (by default) does not map any x-* headers. It also does not map the deliveryMode to the amqp_deliveryMode header, to avoid propagation of that header from an inbound message to an outbound message. Instead, this header is mapped to amqp_receivedDeliveryMode, which is not mapped on output.

Starting with version 4.3, patterns in the header mappings can be negated by preceding the pattern with !. Negated patterns get priority, so a list such as STANDARD_REQUEST_HEADERS,thing1,ba*,!thing2,!thing3,qux,!thing1 does not map thing1 (nor thing2 nor thing3). The standard headers plus bad and qux are mapped. The negation technique can be useful for example to not map JSON type headers for incoming messages when a JSON deserialization logic is done in the receiver downstream different way. For this purpose a !json_* pattern should be configured for header mapper of the inbound channel adapter/gateway.

If you have a user-defined header that begins with ! that you do wish to map, you need to escape it with \, as follows: STANDARD_REQUEST_HEADERS,\!myBangHeader. The header named !myBangHeader is now mapped.
Starting with version 5.1, the DefaultAmqpHeaderMapper will fall back to mapping MessageHeaders.ID and MessageHeaders.TIMESTAMP to MessageProperties.messageId and MessageProperties.timestamp respectively, if the corresponding amqp_messageId or amqp_timestamp headers are not present on outbound messages. Inbound properties will be mapped to the amqp_* headers as before. It is useful to populate the messageId property when message consumers are using stateful retry.

The contentType Header

Unlike other headers, the AmqpHeaders.CONTENT_TYPE is not prefixed with amqp_; this allows transparent passing of the contentType header across different technologies. For example an inbound HTTP message sent to a RabbitMQ queue.

The contentType header is mapped to Spring AMQP’s MessageProperties.contentType property and that is subsequently mapped to RabbitMQ’s content_type property.

Prior to version 5.1, this header was also mapped as an entry in the MessageProperties.headers map; this was incorrect and, furthermore, the value could be wrong since the underlying Spring AMQP message converter might have changed the content type. Such a change would be reflected in the first-class content_type property, but not in the RabbitMQ headers map. Inbound mapping ignored the headers map value. contentType is no longer mapped to an entry in the headers map.