A very simple example with Spring Integration 5.3.2: a single integration flow, registered using the spring-integration DSL with the IntegrationFlowContext:
`
MessageChannel startChannel = MessageChannels.direct("channel").get();
StandardIntegrationFlow flow = IntegrationFlows.from(startChannel)
.log().get();
flowContext.registration(flow)
.autoStartup(false)
.register();
flow.start();
startChannel.send(MessageBuilder.withPayload("test").build());`
Yields org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel.
Why? Adding a single .transform(e->e) (for example) resolves the problem, but obviously is a strange workaround.
That’s definitely an expected behavior. You declare a MessageChannel and send a message into it, but there are no subscribers declared for that channel . Therefore you really see a difference when you add that transform(). You should decide for yourself what is your logic and what you would like to do when there is the message in that channel. You may consider to use other channel types, but still consider to process messages somehow.
Related
I'm writing a Spring Integration application which receives messages from an input system, transforms them and sends them to an output system. The connection to the output system is not always available. The messages from the input system can come at any moment. In case if they are coming when the output system is not available, they shouldn't be lost and send eventually when the output system is available. So I store the messages from the input system in a QueueChannel:
#Configuration
class TcInFlowConfiguration {
#Bean
fun tcInFlow(
#Qualifier(TC_MESSAGE_LISTENER) listener: MessageProducerSupport,
#Qualifier(TC_MESSAGE_CHANNEL) messageChannel: MessageChannel
): IntegrationFlow {
return IntegrationFlow
.from(listener)
.transform { msg: ByteArray -> RamsesTcFrame.deserialize(msg) }
.channel(messageChannel)
.get()
}
#Bean
#Qualifier(TC_MESSAGE_CHANNEL)
fun tcMessageChannel(): MessageChannel {
return MessageChannels.queue().get()
}
The app receives an API call to open/close the connection to the output system, so I create and remove the output integration flow programmatically via IntegrationFlowContext:
val outFlow = IntegrationFlow
.from(TC_MESSAGE_CHANNEL)
.handle(createMessageSender())
.get()
integrationFlowContext.registration(outFlow).register()
When the messages are polled from the queue to be processed by the outFlow, the default Spring task executor is used (I see "scheduling-1" as a thread name in logs). The problem is that I have multiple independent integration flows in the app with the multiple queue channels, so they all got mixed up by being processed by the same task executor. What I want is to process each flow in its own dedicated thread, so the flows won't block each other. How can I achieve this?
Spring Boot v3.0.2, Spring v6.0.4
I tried setting a task scheduler for my QueueChannel:
val queueChannel = MessageChannels.queue().get()
queueChannel.setTaskScheduler(taskScheduler)
It didn't have any effect, taskScheduler seems to be simply not used by QueueChannel implementation.
I tried using ExecutorChannel instead of QueueChannel which supports setting a custom Executor. Unfortunately, ExecutorChannel doesn't buffer messages in memory, so if there are no subscribers to the channel the messages are lost.
Finally, I tried defining a poller in the outFlow to poll the messages from the QueueChannel:
IntegrationFlow
.from(TC_MESSAGE_CHANNEL)
.handle(createMessageSender()) { e -> e.poller(Pollers.fixedDelay(10).taskExecutor(taskExecutor)) }
.get()
This didn't work either. After the connection to the output system is closed and the outFlow is removed, the intermediate channel created by the poller remains in Spring context. So when the new message arrives in QueueChannel it goes to that intermediate channel which is a subscribable channel without subscribers, so the message is lost.
That's correct. The QueueChannel is just a buffer for messages. It really only matters how you consume messages from there. And the common way is to use a PollingConsumer like you do with that e.poller(). It is also correct to configure a taskExecutor() if you don't like to have your messages to be consumed by a TaskScheduler's thread. Not sure what you talk about an "intermediate channel" since it doesn't look like you have one declared in your outFlow. You have that .from(TC_MESSAGE_CHANNEL) and then immediately a handle() with a proper poller. So, no any extra channel in between or after. Unless you do something else in your createMessageSender().
I would suggest do not have a dynamic flow, but rather singleton one for that output system. The QueueChannel can be configured for a persistent message store and poller can be transactional. So, if no connection to a target system, the transaction is going to be rolled back and message remains in the store: https://docs.spring.io/spring-integration/docs/current/reference/html/system-management.html#message-store.
You also can just stop() a polling consumer for that handle() when no connection, so no messages are polled from the queue at that moment.
I am trying to test a Spring Integration flow that starts off from a message-driven-channel-adapter configured as:
<int-jms:message-driven-channel-adapter id="myAdapter" ... />
My test goes like:
#SpringJUnitConfig(locations = {"my-app-context.xml"})
#SpringIntegrationTest(noAutoStartup = {"myAdapter"})
public class MyIntegrationFlowTest {
#Autowired
private MockIntegrationContext mockIntegrationContext;
#Test
public void myTest() {
...
MessageSource<String> messageSource = () -> new GenericMessage<>("foo");
mockIntegrationContext.substituteMessageSourceFor("myAdapter", messageSource);
...
}
}
I am however getting the following error:
org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'myAdapter' is expected to be of type 'org.springframework.integration.endpoint.SourcePollingChannelAdapter' but was actually of type 'org.springframework.integration.jms.JmsMessageDrivenEndpoint'
How should one specify an alternate source for the channel adapter for testing using the MockIntegrationContext, or by some other method?
The Message Driver Channel Adapter is really not a Source Polling Channel Adapter. So, the substituteMessageSourceFor() is indeed cannot be used for that type of components, which, essentially is a MessageProducerSupport implementation, not a SourcePollingChannelAdapter for a MessageSource.
The difference exists because not all protocols provides a listener-like hooks to spawn some self-managed task to subscribe to. The good example is JDBC, which is only passive system expecting requests. Therefore a polling channel adapter with a JdbcPollingChannelAdapter (which is a MessageSource) implementation must be used to interact with DB in event-driven manner.
Other systems (like JMS in your case) provides some listener (or consumer) API for what we can spawn a while task (see MessageListenerContainer in spring-jms) and let its MessageProducerSupport to emit messages to the channel.
Therefore you need to distinguish for yourself with what type of component you interact before choosing a testing strategy.
Since there is no extra layer in case of message-driver channel adapter, but rather some specific, self-managed MessageProducerSupport impl, we not only provide a particular mocking API, but even don't require to know anything else, but just standard unit testing feature and a message channel this endpoint is producing in the configuration.
So, the solution for you is something like:
#SpringIntegrationTest(noAutoStartup = {"myAdapter"}) - that's fully correct in your code: we really have to stop the real channel adapter to not pollute our testing environment.
You just need to inject into your test class a MessageChannel that id="myAdapter" is producing to. In your test code you just build a Message and send it into this channel. No need to worry about a MockIntegrationContext at all.
I did one simple DSL which retrieves the data from database and doing simple conversion in the service activator.
#Bean
public IntegrationFlow mainFlow() {
return IntegrationFlows.from("userChannel")
.channel("queryChannel")
.handle("sampleConvertor","convertUser")
.get();
queryChannel is a jdbc outbound gateway and sampleConverter is the service Activator.
<int-jdbc:outbound-gateway query="select * from employee where employee_id=:payload"
request-channel="queryChannel" data-source="dataSource"/>
The issue is after retrieving the data from database, the flow is not going to serviceActivator and it simply returns back the database response.
In xml configuration, I used to invoke gateway inside the chain like below.
<int:gateway id="query.gateway" request-channel="queryChannel"/>
Please suggest what I am doing wrong here. Thanks in advance.
That's a bit unusual to combine Java DSL and XML configuration, but they still work together.
Your problem I think that you are missing the fact that your queryChannel has two subscriber at runtime, not a chain of call.
The first one is <int-jdbc:outbound-gateway> and the second is that .handle("sampleConvertor","convertUser"). Right, when you declare a channel in the IntegrationFlow, the next EIP-method produces a subscriber for this channel. At the same time when you use a channel like request-channel or input-channel in the XML configuration that brings a subscriber as well.
So, you have two subscriber on the DirectChannel with the RoundRobinLoadBalancingStrategy and therefore only one of them will handle a message and if it is a request-replly component, like that <int-jdbc:outbound-gateway> it will produce a message into the output-channel or to the replyChannel in the headers. In your case the story is exactly about a replyChannel and therefore you don't go to the .handle("sampleConvertor","convertUser") because it's not the next in the chain, but just a parallel universe by the round-robin algorithm.
If you really would like to reach that .handle("sampleConvertor","convertUser") after calling the <int-jdbc:outbound-gateway>, you should consider to use .gateway("queryChannel") instead of that .channel().
I'm currently implementing a flow on a Spring Integration-based (ver. 3.0.1.RELEASE) application that requires to store messages on a JMS queue to be picked up later.
For that, I've been trying to use a Spring Integration JMS Inbound Channel Adapter with a custom selector, and then picking up the message from the queue by changing the JMS selector of the JMSDestinationPollingSource to some matching ID included as a header property.
One of the requirements for this is that I cannot add a new service or a JAVA method, so I've been trying to sort it out using a Control Bus, but keep receiving the same error when I send the message to set the messageSelector to something different.
Inbound Channel Adapter definition:
<int-jms:inbound-channel-adapter id="inboundAdapter"
channel="inboundChannel"
destinationName="bufferQueue"
connection-factory="connectionFactory"
selector="matchingID = 'NO VALUE'">
<int:poller fixed-delay="1000"/>
</int-jms:inbound-channel-adapter>
Message:
#'inboundAdapter.source'.setMessageSelector("matchingID = 'VALUE'")
Error:
EvaluationException: The method 'public void org.springframework.integration.jms.JmsDestinationPollingSource.setMessageSelector(java.lang.String)' is not supported by this command processor. If usign the Control Bus, consider adding #ManagedOperation or #ManagedAttribute.
Which, AFAIK, means that the JmsDestinationPollingSource class is not Control Bus manageable, as it's not passing the ControlBusMethodFilter.
Is this approach nonviable, or is there something I'm missing? Is there any way to set the selector dynamically using SI XML configuration files only?
First of all it is strange to use Java tool and don't allow to write code on Java...
But that is your choice, or as you said requirements.
Change the employer! ;-)
That's correct: Control Bus allows only #ManagedOperation and #ManagedAttribute method. Since JmsDestinationPollingSource.setMessageSelector. We can make it like that. But does it make so much sense if we can reach it a bit different approach?
<int:outbound-channel-adapter id="changeSelectorChannel"
ref"inboundAdapter.source method="setMessageSelector"/>
where a new selector expression should be as a payload of the Message to this channel.
In my application i have service activator which is taking message in input-channel, doing some process in activator method and putting back the processed message into output-channel to saving in db using mongo-adapter.
I have declare output-channel like <int-channel id="outputchannel"/>
In my junit test to test the message in outputchannel i used as below.
<bridge input-channel="outputchannel" output-channel="testInputChannel">
The testInputChannel is declared as QueueChannel
Still the message is going mongo-adapter input-channel="outputchannel".
Do i need to definitely declare outputchannel as pub-sub channel. Otherwise it won't come to testInputChannel
With two subscribers, the messages will be sent to the mongo adapter and bridge in round-robin fashion.
To test, you could have your test replace the channel with a pub/sub.
Or stop() the mongo adapter; which is generally better for test cases.
You can use auto-startup="${should.start}" and use a property to not start the adapter in test cases, but start it for production.
The mongo adapter won't be subscribed to the channel until it is start() ed.
Or, if your test only sends one message, make sure the bridge is the first subscriber to the channel.