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127 lines
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<title>30. Configuration Options</title><link rel="stylesheet" type="text/css" href="css/manual-multipage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="multi_spring-cloud.html" title="Spring Cloud"><link rel="up" href="multi__spring_cloud_stream.html" title="Part V. Spring Cloud Stream"><link rel="prev" href="multi_spring-cloud-stream-overview-binders.html" title="29. Binders"><link rel="next" href="multi_content-type-management.html" title="31. Content Type Negotiation"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">30. Configuration Options</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="multi_spring-cloud-stream-overview-binders.html">Prev</a> </td><th width="60%" align="center">Part V. Spring Cloud Stream</th><td width="20%" align="right"> <a accesskey="n" href="multi_content-type-management.html">Next</a></td></tr></table><hr></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_configuration_options" href="#_configuration_options"></a>30. Configuration Options</h2></div></div></div><p>Spring Cloud Stream supports general configuration options as well as configuration for bindings and binders.
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Some binders let additional binding properties support middleware-specific features.</p><p>Configuration options can be provided to Spring Cloud Stream applications through any mechanism supported by Spring Boot.
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This includes application arguments, environment variables, and YAML or .properties files.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_binding_service_properties" href="#_binding_service_properties"></a>30.1 Binding Service Properties</h2></div></div></div><p>These properties are exposed via <code class="literal">org.springframework.cloud.stream.config.BindingServiceProperties</code></p><div class="variablelist"><dl class="variablelist"><dt><span class="term">spring.cloud.stream.instanceCount</span></dt><dd><p class="simpara">The number of deployed instances of an application.
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Must be set for partitioning on the producer side. Must be set on the consumer side when using RabbitMQ and with Kafka if <code class="literal">autoRebalanceEnabled=false</code>.</p><p class="simpara">Default: <code class="literal">1</code>.</p></dd><dt><span class="term">spring.cloud.stream.instanceIndex</span></dt><dd>The instance index of the application: A number from <code class="literal">0</code> to <code class="literal">instanceCount - 1</code>.
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Used for partitioning with RabbitMQ and with Kafka if <code class="literal">autoRebalanceEnabled=false</code>.
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Automatically set in Cloud Foundry to match the application’s instance index.</dd><dt><span class="term">spring.cloud.stream.dynamicDestinations</span></dt><dd><p class="simpara">A list of destinations that can be bound dynamically (for example, in a dynamic routing scenario).
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If set, only listed destinations can be bound.</p><p class="simpara">Default: empty (letting any destination be bound).</p></dd><dt><span class="term">spring.cloud.stream.defaultBinder</span></dt><dd><p class="simpara">The default binder to use, if multiple binders are configured.
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See <a class="link" href="multi_spring-cloud-stream-overview-binders.html#multiple-binders" title="29.4 Multiple Binders on the Classpath">Multiple Binders on the Classpath</a>.</p><p class="simpara">Default: empty.</p></dd><dt><span class="term">spring.cloud.stream.overrideCloudConnectors</span></dt><dd><p class="simpara">This property is only applicable when the <code class="literal">cloud</code> profile is active and Spring Cloud Connectors are provided with the application.
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If the property is <code class="literal">false</code> (the default), the binder detects a suitable bound service (for example, a RabbitMQ service bound in Cloud Foundry for the RabbitMQ binder) and uses it for creating connections (usually through Spring Cloud Connectors).
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When set to <code class="literal">true</code>, this property instructs binders to completely ignore the bound services and rely on Spring Boot properties (for example, relying on the <code class="literal">spring.rabbitmq.*</code> properties provided in the environment for the RabbitMQ binder).
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The typical usage of this property is to be nested in a customized environment <a class="link" href="multi_spring-cloud-stream-overview-binders.html#multiple-systems" title="29.5 Connecting to Multiple Systems">when connecting to multiple systems</a>.</p><p class="simpara">Default: <code class="literal">false</code>.</p></dd><dt><span class="term">spring.cloud.stream.bindingRetryInterval</span></dt><dd><p class="simpara">The interval (in seconds) between retrying binding creation when, for example, the binder does not support late binding and the broker (for example, Apache Kafka) is down.
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Set it to zero to treat such conditions as fatal, preventing the application from starting.</p><p class="simpara">Default: <code class="literal">30</code></p></dd></dl></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="binding-properties" href="#binding-properties"></a>30.2 Binding Properties</h2></div></div></div><p>Binding properties are supplied by using the format of <code class="literal">spring.cloud.stream.bindings.<channelName>.<property>=<value></code>.
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The <code class="literal"><channelName></code> represents the name of the channel being configured (for example, <code class="literal">output</code> for a <code class="literal">Source</code>).</p><p>To avoid repetition, Spring Cloud Stream supports setting values for all channels, in the format of <code class="literal">spring.cloud.stream.default.<property>=<value></code>.</p><p>When it comes to avoiding repetitions for extended binding properties, this format should be used - <code class="literal">spring.cloud.stream.<binder-type>.default.<producer|consumer>.<property>=<value></code>.</p><p>In what follows, we indicate where we have omitted the <code class="literal">spring.cloud.stream.bindings.<channelName>.</code> prefix and focus just on the property name, with the understanding that the prefix ise included at runtime.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_common_binding_properties" href="#_common_binding_properties"></a>30.2.1 Common Binding Properties</h3></div></div></div><p>These properties are exposed via <code class="literal">org.springframework.cloud.stream.config.BindingProperties</code></p><p>The following binding properties are available for both input and output bindings and must be prefixed with <code class="literal">spring.cloud.stream.bindings.<channelName>.</code> (for example, <code class="literal">spring.cloud.stream.bindings.input.destination=ticktock</code>).</p><p>Default values can be set by using the <code class="literal">spring.cloud.stream.default</code> prefix (for example`spring.cloud.stream.default.contentType=application/json`).</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">destination</span></dt><dd>The target destination of a channel on the bound middleware (for example, the RabbitMQ exchange or Kafka topic).
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If the channel is bound as a consumer, it could be bound to multiple destinations, and the destination names can be specified as comma-separated <code class="literal">String</code> values.
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If not set, the channel name is used instead.
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The default value of this property cannot be overridden.</dd><dt><span class="term">group</span></dt><dd><p class="simpara">The consumer group of the channel.
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Applies only to inbound bindings.
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See <a class="link" href="multi__main_concepts.html#consumer-groups" title="27.4 Consumer Groups">Consumer Groups</a>.</p><p class="simpara">Default: <code class="literal">null</code> (indicating an anonymous consumer).</p></dd><dt><span class="term">contentType</span></dt><dd><p class="simpara">The content type of the channel.
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See “<a class="xref" href="multi_content-type-management.html" title="31. Content Type Negotiation">Chapter 31, <i>Content Type Negotiation</i></a>”.</p><p class="simpara">Default: <code class="literal">application/json</code>.</p></dd><dt><span class="term">binder</span></dt><dd><p class="simpara">The binder used by this binding.
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See “<a class="xref" href="multi_spring-cloud-stream-overview-binders.html#multiple-binders" title="29.4 Multiple Binders on the Classpath">Section 29.4, “Multiple Binders on the Classpath”</a>” for details.</p><p class="simpara">Default: <code class="literal">null</code> (the default binder is used, if it exists).</p></dd></dl></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_consumer_properties" href="#_consumer_properties"></a>30.2.2 Consumer Properties</h3></div></div></div><p>These properties are exposed via <code class="literal">org.springframework.cloud.stream.binder.ConsumerProperties</code></p><p>The following binding properties are available for input bindings only and must be prefixed with <code class="literal">spring.cloud.stream.bindings.<channelName>.consumer.</code> (for example, <code class="literal">spring.cloud.stream.bindings.input.consumer.concurrency=3</code>).</p><p>Default values can be set by using the <code class="literal">spring.cloud.stream.default.consumer</code> prefix (for example, <code class="literal">spring.cloud.stream.default.consumer.headerMode=none</code>).</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">concurrency</span></dt><dd><p class="simpara">The concurrency of the inbound consumer.</p><p class="simpara">Default: <code class="literal">1</code>.</p></dd><dt><span class="term">partitioned</span></dt><dd><p class="simpara">Whether the consumer receives data from a partitioned producer.</p><p class="simpara">Default: <code class="literal">false</code>.</p></dd><dt><span class="term">headerMode</span></dt><dd><p class="simpara">When set to <code class="literal">none</code>, disables header parsing on input.
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Effective only for messaging middleware that does not support message headers natively and requires header embedding.
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This option is useful when consuming data from non-Spring Cloud Stream applications when native headers are not supported.
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When set to <code class="literal">headers</code>, it uses the middleware’s native header mechanism.
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When set to <code class="literal">embeddedHeaders</code>, it embeds headers into the message payload.</p><p class="simpara">Default: depends on the binder implementation.</p></dd><dt><span class="term">maxAttempts</span></dt><dd><p class="simpara">If processing fails, the number of attempts to process the message (including the first).
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Set to <code class="literal">1</code> to disable retry.</p><p class="simpara">Default: <code class="literal">3</code>.</p></dd><dt><span class="term">backOffInitialInterval</span></dt><dd><p class="simpara">The backoff initial interval on retry.</p><p class="simpara">Default: <code class="literal">1000</code>.</p></dd><dt><span class="term">backOffMaxInterval</span></dt><dd><p class="simpara">The maximum backoff interval.</p><p class="simpara">Default: <code class="literal">10000</code>.</p></dd><dt><span class="term">backOffMultiplier</span></dt><dd><p class="simpara">The backoff multiplier.</p><p class="simpara">Default: <code class="literal">2.0</code>.</p></dd><dt><span class="term">defaultRetryable</span></dt><dd><p class="simpara">Whether exceptions thrown by the listener that are not listed in the <code class="literal">retryableExceptions</code> are retryable.</p><p class="simpara">Default: <code class="literal">true</code>.</p></dd><dt><span class="term">instanceIndex</span></dt><dd><p class="simpara">When set to a value greater than equal to zero, it allows customizing the instance index of this consumer (if different from <code class="literal">spring.cloud.stream.instanceIndex</code>).
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When set to a negative value, it defaults to <code class="literal">spring.cloud.stream.instanceIndex</code>.
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See “<a class="xref" href="multi__inter_application_communication.html#spring-cloud-stream-overview-instance-index-instance-count" title="33.2 Instance Index and Instance Count">Section 33.2, “Instance Index and Instance Count”</a>” for more information.</p><p class="simpara">Default: <code class="literal">-1</code>.</p></dd><dt><span class="term">instanceCount</span></dt><dd><p class="simpara">When set to a value greater than equal to zero, it allows customizing the instance count of this consumer (if different from <code class="literal">spring.cloud.stream.instanceCount</code>).
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When set to a negative value, it defaults to <code class="literal">spring.cloud.stream.instanceCount</code>.
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See “<a class="xref" href="multi__inter_application_communication.html#spring-cloud-stream-overview-instance-index-instance-count" title="33.2 Instance Index and Instance Count">Section 33.2, “Instance Index and Instance Count”</a>” for more information.</p><p class="simpara">Default: <code class="literal">-1</code>.</p></dd><dt><span class="term">retryableExceptions</span></dt><dd><p class="simpara">A map of Throwable class names in the key and a boolean in the value.
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Specify those exceptions (and subclasses) that will or won’t be retried.
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Also see <code class="literal">defaultRetriable</code>.
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Example: <code class="literal">spring.cloud.stream.bindings.input.consumer.retryable-exceptions.java.lang.IllegalStateException=false</code>.</p><p class="simpara">Default: empty.</p></dd><dt><span class="term">useNativeDecoding</span></dt><dd><p class="simpara">When set to <code class="literal">true</code>, the inbound message is deserialized directly by the client library, which must be configured correspondingly (for example, setting an appropriate Kafka producer value deserializer).
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When this configuration is being used, the inbound message unmarshalling is not based on the <code class="literal">contentType</code> of the binding.
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When native decoding is used, it is the responsibility of the producer to use an appropriate encoder (for example, the Kafka producer value serializer) to serialize the outbound message.
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Also, when native encoding and decoding is used, the <code class="literal">headerMode=embeddedHeaders</code> property is ignored and headers are not embedded in the message.
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See the producer property <code class="literal">useNativeEncoding</code>.</p><p class="simpara">Default: <code class="literal">false</code>.</p></dd></dl></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_producer_properties" href="#_producer_properties"></a>30.2.3 Producer Properties</h3></div></div></div><p>These properties are exposed via <code class="literal">org.springframework.cloud.stream.binder.ProducerProperties</code></p><p>The following binding properties are available for output bindings only and must be prefixed with <code class="literal">spring.cloud.stream.bindings.<channelName>.producer.</code> (for example, <code class="literal">spring.cloud.stream.bindings.input.producer.partitionKeyExpression=payload.id</code>).</p><p>Default values can be set by using the prefix <code class="literal">spring.cloud.stream.default.producer</code> (for example, <code class="literal">spring.cloud.stream.default.producer.partitionKeyExpression=payload.id</code>).</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">partitionKeyExpression</span></dt><dd><p class="simpara">A SpEL expression that determines how to partition outbound data.
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If set, or if <code class="literal">partitionKeyExtractorClass</code> is set, outbound data on this channel is partitioned. <code class="literal">partitionCount</code> must be set to a value greater than 1 to be effective.
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Mutually exclusive with <code class="literal">partitionKeyExtractorClass</code>.
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See “<a class="xref" href="multi__main_concepts.html#partitioning" title="27.6 Partitioning Support">Section 27.6, “Partitioning Support”</a>”.</p><p class="simpara">Default: null.</p></dd><dt><span class="term">partitionKeyExtractorClass</span></dt><dd><p class="simpara">A <code class="literal">PartitionKeyExtractorStrategy</code> implementation.
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If set, or if <code class="literal">partitionKeyExpression</code> is set, outbound data on this channel is partitioned. <code class="literal">partitionCount</code> must be set to a value greater than 1 to be effective.
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Mutually exclusive with <code class="literal">partitionKeyExpression</code>.
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See “<a class="xref" href="multi__main_concepts.html#partitioning" title="27.6 Partitioning Support">Section 27.6, “Partitioning Support”</a>”.</p><p class="simpara">Default: <code class="literal">null</code>.</p></dd><dt><span class="term">partitionSelectorClass</span></dt><dd><p class="simpara"> A <code class="literal">PartitionSelectorStrategy</code> implementation.
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Mutually exclusive with <code class="literal">partitionSelectorExpression</code>.
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If neither is set, the partition is selected as the <code class="literal">hashCode(key) % partitionCount</code>, where <code class="literal">key</code> is computed through either <code class="literal">partitionKeyExpression</code> or <code class="literal">partitionKeyExtractorClass</code>.</p><p class="simpara">Default: <code class="literal">null</code>.</p></dd><dt><span class="term">partitionSelectorExpression</span></dt><dd><p class="simpara">A SpEL expression for customizing partition selection.
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Mutually exclusive with <code class="literal">partitionSelectorClass</code>.
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If neither is set, the partition is selected as the <code class="literal">hashCode(key) % partitionCount</code>, where <code class="literal">key</code> is computed through either <code class="literal">partitionKeyExpression</code> or <code class="literal">partitionKeyExtractorClass</code>.</p><p class="simpara">Default: <code class="literal">null</code>.</p></dd><dt><span class="term">partitionCount</span></dt><dd><p class="simpara">The number of target partitions for the data, if partitioning is enabled.
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Must be set to a value greater than 1 if the producer is partitioned.
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On Kafka, it is interpreted as a hint. The larger of this and the partition count of the target topic is used instead.</p><p class="simpara">Default: <code class="literal">1</code>.</p></dd><dt><span class="term">requiredGroups</span></dt><dd>A comma-separated list of groups to which the producer must ensure message delivery even if they start after it has been created (for example, by pre-creating durable queues in RabbitMQ).</dd><dt><span class="term">headerMode</span></dt><dd><p class="simpara">When set to <code class="literal">none</code>, it disables header embedding on output.
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It is effective only for messaging middleware that does not support message headers natively and requires header embedding.
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This option is useful when producing data for non-Spring Cloud Stream applications when native headers are not supported.
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When set to <code class="literal">headers</code>, it uses the middleware’s native header mechanism.
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When set to <code class="literal">embeddedHeaders</code>, it embeds headers into the message payload.</p><p class="simpara">Default: Depends on the binder implementation.</p></dd><dt><span class="term">useNativeEncoding</span></dt><dd><p class="simpara">When set to <code class="literal">true</code>, the outbound message is serialized directly by the client library, which must be configured correspondingly (for example, setting an appropriate Kafka producer value serializer).
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When this configuration is being used, the outbound message marshalling is not based on the <code class="literal">contentType</code> of the binding.
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When native encoding is used, it is the responsibility of the consumer to use an appropriate decoder (for example, the Kafka consumer value de-serializer) to deserialize the inbound message.
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Also, when native encoding and decoding is used, the <code class="literal">headerMode=embeddedHeaders</code> property is ignored and headers are not embedded in the message.
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See the consumer property <code class="literal">useNativeDecoding</code>.</p><p class="simpara">Default: <code class="literal">false</code>.</p></dd><dt><span class="term">errorChannelEnabled</span></dt><dd><p class="simpara">When set to <code class="literal">true</code>, if the binder supports asynchroous send results, send failures are sent to an error channel for the destination.
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See “<a class="xref" href="">???</a>” for more information.</p><p class="simpara">Default: <code class="literal">false</code>.</p></dd></dl></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="dynamicdestination" href="#dynamicdestination"></a>30.3 Using Dynamically Bound Destinations</h2></div></div></div><p>Besides the channels defined by using <code class="literal">@EnableBinding</code>, Spring Cloud Stream lets applications send messages to dynamically bound destinations.
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This is useful, for example, when the target destination needs to be determined at runtime.
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Applications can do so by using the <code class="literal">BinderAwareChannelResolver</code> bean, registered automatically by the <code class="literal">@EnableBinding</code> annotation.</p><p>The 'spring.cloud.stream.dynamicDestinations' property can be used for restricting the dynamic destination names to a known set (whitelisting).
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If this property is not set, any destination can be bound dynamically.</p><p>The <code class="literal">BinderAwareChannelResolver</code> can be used directly, as shown in the following example of a REST controller using a path variable to decide the target channel:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@EnableBinding</span></em>
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<em><span class="hl-annotation" style="color: gray">@Controller</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> SourceWithDynamicDestination {
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<em><span class="hl-annotation" style="color: gray">@Autowired</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> BinderAwareChannelResolver resolver;
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<em><span class="hl-annotation" style="color: gray">@RequestMapping(path = "/{target}", method = POST, consumes = "*/*")</span></em>
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<em><span class="hl-annotation" style="color: gray">@ResponseStatus(HttpStatus.ACCEPTED)</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> handleRequest(<em><span class="hl-annotation" style="color: gray">@RequestBody</span></em> String body, <em><span class="hl-annotation" style="color: gray">@PathVariable("target")</span></em> target,
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<em><span class="hl-annotation" style="color: gray">@RequestHeader(HttpHeaders.CONTENT_TYPE)</span></em> Object contentType) {
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sendMessage(body, target, contentType);
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}
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> sendMessage(String body, String target, Object contentType) {
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resolver.resolveDestination(target).send(MessageBuilder.createMessage(body,
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> MessageHeaders(Collections.singletonMap(MessageHeaders.CONTENT_TYPE, contentType))));
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}
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}</pre><p>Now consider what happens when we start the application on the default port (8080) and make the following requests with CURL:</p><pre class="screen">curl -H "Content-Type: application/json" -X POST -d "customer-1" http://localhost:8080/customers
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curl -H "Content-Type: application/json" -X POST -d "order-1" http://localhost:8080/orders</pre><p>The destinations, 'customers' and 'orders', are created in the broker (in the exchange for Rabbit or in the topic for Kafka) with names of 'customers' and 'orders', and the data is published to the appropriate destinations.</p><p>The <code class="literal">BinderAwareChannelResolver</code> is a general-purpose Spring Integration <code class="literal">DestinationResolver</code> and can be injected in other components — for example, in a router using a SpEL expression based on the <code class="literal">target</code> field of an incoming JSON message. The following example includes a router that reads SpEL expressions:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@EnableBinding</span></em>
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<em><span class="hl-annotation" style="color: gray">@Controller</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> SourceWithDynamicDestination {
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<em><span class="hl-annotation" style="color: gray">@Autowired</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> BinderAwareChannelResolver resolver;
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<em><span class="hl-annotation" style="color: gray">@RequestMapping(path = "/", method = POST, consumes = "application/json")</span></em>
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<em><span class="hl-annotation" style="color: gray">@ResponseStatus(HttpStatus.ACCEPTED)</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> handleRequest(<em><span class="hl-annotation" style="color: gray">@RequestBody</span></em> String body, <em><span class="hl-annotation" style="color: gray">@RequestHeader(HttpHeaders.CONTENT_TYPE)</span></em> Object contentType) {
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sendMessage(body, contentType);
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}
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">private</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> sendMessage(Object body, Object contentType) {
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routerChannel().send(MessageBuilder.createMessage(body,
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> MessageHeaders(Collections.singletonMap(MessageHeaders.CONTENT_TYPE, contentType))));
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}
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<em><span class="hl-annotation" style="color: gray">@Bean(name = "routerChannel")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> MessageChannel routerChannel() {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> DirectChannel();
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}
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<em><span class="hl-annotation" style="color: gray">@Bean</span></em>
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<em><span class="hl-annotation" style="color: gray">@ServiceActivator(inputChannel = "routerChannel")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> ExpressionEvaluatingRouter router() {
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ExpressionEvaluatingRouter router =
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> ExpressionEvaluatingRouter(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> SpelExpressionParser().parseExpression(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"payload.target"</span>));
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router.setDefaultOutputChannelName(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"default-output"</span>);
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router.setChannelResolver(resolver);
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> router;
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}
|
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}</pre><p>The <a class="link" href="https://github.com/spring-cloud-stream-app-starters/router" target="_top">Router Sink Application</a> uses this technique to create the destinations on-demand.</p><p>If the channel names are known in advance, you can configure the producer properties as with any other destination.
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Alternatively, if you register a <code class="literal">NewBindingCallback<></code> bean, it is invoked just before the binding is created.
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The callback takes the generic type of the extended producer properties used by the binder.
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It has one method:</p><pre class="programlisting"><span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> configure(String channelName, MessageChannel channel, ProducerProperties producerProperties,
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T extendedProducerProperties);</pre><p>The following example shows how to use the RabbitMQ binder:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@Bean</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> NewBindingCallback<RabbitProducerProperties> dynamicConfigurer() {
|
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> (name, channel, props, extended) -> {
|
|
props.setRequiredGroups(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"bindThisQueue"</span>);
|
|
extended.setQueueNameGroupOnly(true);
|
|
extended.setAutoBindDlq(true);
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|
extended.setDeadLetterQueueName(<span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"myDLQ"</span>);
|
|
};
|
|
}</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left">Note</th></tr><tr><td align="left" valign="top"><p>If you need to support dynamic destinations with multiple binder types, use <code class="literal">Object</code> for the generic type and cast the <code class="literal">extended</code> argument as needed.</p></td></tr></table></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="multi_spring-cloud-stream-overview-binders.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="multi__spring_cloud_stream.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="multi_content-type-management.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">29. Binders </td><td width="20%" align="center"><a accesskey="h" href="multi_spring-cloud.html">Home</a></td><td width="40%" align="right" valign="top"> 31. Content Type Negotiation</td></tr></table></div></body></html> |