For the latest stable version, please use Spring Integration 6.4.1!

Inbound Channel Adapters

Typically, message flows start from an inbound channel adapter (such as <int-jdbc:inbound-channel-adapter>). The adapter is configured with <poller>, and it asks a MessageSource<?> to periodically produce messages. Java DSL allows for starting IntegrationFlow from a MessageSource<?>, too. For this purpose, the IntegrationFlow fluent API provides an overloaded IntegrationFlow.from(MessageSource<?> messageSource) method. You can configure the MessageSource<?> as a bean and provide it as an argument for that method. The second parameter of IntegrationFlow.from() is a Consumer<SourcePollingChannelAdapterSpec> lambda that lets you provide options (such as PollerMetadata or SmartLifecycle) for the SourcePollingChannelAdapter. The following example shows how to use the fluent API and a lambda to create an IntegrationFlow:

@Bean
public MessageSource<Object> jdbcMessageSource() {
    return new JdbcPollingChannelAdapter(this.dataSource, "SELECT * FROM something");
}

@Bean
public IntegrationFlow pollingFlow() {
    return IntegrationFlow.from(jdbcMessageSource(),
                c -> c.poller(Pollers.fixedRate(100).maxMessagesPerPoll(1)))
            .transform(Transformers.toJson())
            .channel("furtherProcessChannel")
            .get();
}

For those cases that have no requirements to build Message objects directly, you can use a IntegrationFlow.fromSupplier() variant that is based on the java.util.function.Supplier . The result of the Supplier.get() is automatically wrapped in a Message (if it is not already a Message).