Error handling (async) with splitter -> service activator -> aggregator

I'm looking for the correct way/pattern how to deal with errors in a service activator after a splitter.

I need to split up an XML-file for parallel processing by a task executor pool.
The successfully processed messages (they are sent to a remote system using rmi) need to be aggregated to an output file and I'd like to output errors (the ones rejected by the remote system) to a different file.

What is the preferred way to model this with Spring Integration?

Specifically, how do I deal with aggregation of the successes and the errors/exceptions?

I've looked in the reference manual and in the Apress book, but I can't seem to find a suggestion on how to deal with this use-case.

Thanks in advance!

Stefan

There are a number of ways to do it; one would be something like...

Code:

---


...splitter->sagateway->service------------------->aggregator->transformTo2Lists->splitter->...
              |                                |
              |->errorChannel->transformErrors->|

---

The sagateway would be a <service-activator/> that references a <gateway/> allowing you to insert error handling mid-flow.

Code:

---

<service-activator ... ref="gw" />

<gateway id="gw" service-interface="foo.GW" default-request-channel="toService" errorChannel="myErrors" />

---

Hi Gary,
Thanks for the quick reply.

I think I get it. I assume the aggregator will have to work on SI's GenericMessage and ErrorMessage in order to distinguish good from bad apples?

Best regards,
Stefan

No; the aggregator doesn't care about the types (in this scenario - like I said there are many ways to do this - I just feel the above is one of the simplest).

The main flow produces objects of type GoodGuy and the error flow objects of type BadGuy; the aggregator will simply create a list of objects (mixed). Then, a custom transformer produces two lists...

Notice in the error flow I included a transformer - transform the ErrorMessage into a BadGuy object.

Code:

---

public List<List<Object>> transform(List<Object> list) {...}

---

...which you can then split into two messages (with a standard <splitter/>) and route each to a different channel based on the type of the objects in the list.

In fact, if you make the transformer above create lists that are wrapped in a type, it might make it even easier...

Code:

---

public abstract class GuyList { ... } // simple wrapper for a list object.

public class BadGuys extends GuyList {}

public class GoodGuys extends GuyList {}

...

public class SortGoodFromBadTransformer {

    public List<GuyList> transform(List<Object> list) {...}

}

---

Then, downstream of the splitter you can use a payload type router to route BadGuys to one adapter and GoodGuys to another,

Thanks Gary! That makes perfect sense!
Much appreciated!

All the best,
Stefan

This is (more or less) the use case I'm looking for. In order to process messages in parallel (i.e. in different threads) I tried to use dispatcher task-executor="executor" on the splitter's outgoing channel but it doesn't seem to work (e.g. "Dispatcher has no subscribers").

Can you please post your xml configuration?

Thanks.