How to periodically publish a message to activemq spring integration DSL

Question

I installed Active MQ and periodically say every 10 seconds want to send a message to "my.queue"

I'm struggling to comprehend Spring Integration DSL language.

I need something like

IntegrationFlows.from(every 5 seconds)
 .send(message to "my.queue")

Answer 1

Yes, you can do that with Spring Integration Java DSL and its IntegrationFlow abstraction. To make a periodic task you need to use this factory in the IntegrationFlows to start the flow:

/**
 * Provides {@link Supplier} as source of messages to the integration flow.
 * which will be triggered by a <b>provided</b>
 * {@link org.springframework.integration.endpoint.SourcePollingChannelAdapter}.
 * @param messageSource the {@link Supplier} to populate.
 * @param endpointConfigurer the {@link Consumer} to provide more options for the
 * {@link org.springframework.integration.config.SourcePollingChannelAdapterFactoryBean}.
 * @param <T> the supplier type.
 * @return new {@link IntegrationFlowBuilder}.
 * @see Supplier
 */
public static <T> IntegrationFlowBuilder fromSupplier(Supplier<T> messageSource,
        Consumer<SourcePollingChannelAdapterSpec> endpointConfigurer) {

The Supplier may return an object you'd like to send as a payload downstream. The second consumer arg can be configured with the:

.poller(p -> p.fixedDelay(1000))

This way every second a message is going to be created from the supplied payload and sent downstream.

To send a message ti Active MQ, you need to use a org.springframework.integration.jms.dsl.Jms and its method for respective channel adapter:

/**
 * The factory to produce a {@link JmsOutboundChannelAdapterSpec}.
 * @param connectionFactory the JMS ConnectionFactory to build on
 * @return the {@link JmsOutboundChannelAdapterSpec} instance
 */
public static JmsOutboundChannelAdapterSpec.JmsOutboundChannelSpecTemplateAware outboundAdapter(
        ConnectionFactory connectionFactory) {

The result of this factory has to be used in the DSL callback like:

/**
 * Populate a {@link ServiceActivatingHandler} for the provided
 * {@link MessageHandler} implementation.
 * Can be used as Java 8 Lambda expression:
 * <pre class="code">
 * {@code
 *  .handle(m -> logger.info(m.getPayload())
 * }
 * </pre>
 * @param messageHandler the {@link MessageHandler} to use.
 * @return the current {@link BaseIntegrationFlowDefinition}.
 */
public B handle(MessageHandler messageHandler) {

All the info is present in the docs: https://docs.spring.io/spring-integration/reference/html/dsl.html#java-dsl

Something like this:

@Bean
public IntegrationFlow jmsPeriodicFlow() {
    return IntegrationFlows.fromSupplier(() -> "hello", 
                               e -> e.poller(p -> p.fixedDelay(5000)))
            .handle(Jms.outboundAdapter(jmsConnectionFactory())
                    .destination("my.queue"))
            .get();
}