How can I easily add and remove message conversion logic into a processing flow in Spring Integration?

Question

I've been playing with Spring integration, and I can't see how best to solve the following problem.

Say I have XML messages arriving onto a channel. These messages may have arbitrary structure, and I want to convert them to my canonical form, so I think I want to write custom converters for each type of structure, so that I can do whatever processing and error-checking I want.

The obvious thing is to wire up a router to have a look at the messages and route to an appropriate converter, but I think this means I need to hard-code the processing flow onto a channel pointing at each converter.

I'd like to avoid hard-configuring in the different converters and routing logic, and the alternative that springs to mind is to have a set of converters that implement some kind of boolean canHandle(message), so that we just show the message to each converter until one 'claims' the message or we run out. This way, it seems like I might be able to annotate the converters into the configuration without actually modifying the processing flow.

I'm new to Spring integration and I may well be mis-thinking this. Is there a stock way to do this in Spring integration, have I missed something or am I going about it all wrong?

Gary Russell Gary Russell · Accepted Answer · 2012-08-03T13:51:15

There are a number of ways to do this. The first one that came to mind is a recipient list router with selector expressions:

<recipient-list-router id="simpleDynamicRouter" input-channel="simpleDynamicInput">
    <recipient selector-expression="@handler1.canHandle(payload)" channel="toHandler1"/>
    <recipient selector-expression="@handler2.canHandle(payload)" channel="toHandler2"/>
    <recipient selector-expression="@handler3.canHandle(payload)" channel="toHandler3"/>    
</recipient-list-router>

<transformer ... ref="handler1" />
<transformer ... ref="handler2" />
<transformer ... ref="handler3" />

Where handler1 etc are <bean/>s with your implementation, and canHandle() method.

Another option is to write your own custom dynamic router; there's an example of how to do that here https://github.com/SpringSource/spring-integration-samples/tree/master/advanced/dynamic-ftp

How can I easily add and remove message conversion logic into a processing flow in Spring Integration?

1 Answers