THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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You can get hold of the org.apache.camel.spi.UnitOfWork from org.apache.camel.Exchange with the method getUnitOfWork().
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From Camel 2.14: onCompletion has been modified to support running the completion task in either synchronous or asynchronous mode (using a thread pool) and also whether to run before or after the route consumer is done. The reason is to give more flexibility. For example to specify to run synchronous and before the route consumer is done, which allows to modify the exchange before the consumer writes back any response to the callee. You can use this to for example add customer headers, or send to a log to log the response message, etc.
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The onCompletion has changed defaults and behavior from Camel 2.14: it now runs
- Runs synchronously without any thread pool
In Camel 2.13 the defaults were
- Runs asynchronous using a thread pool
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The onCompletion runs in a separate thread in parallel with the original route. It is therefore not intended to influence the outcome of the original route. The idea for on completion is to spin off a new thread to e.g., send logs to a central log database, send an email, send alerts to a monitoring system, store a copy of the result message etc.
Therefore if you want to do some work that influence the original route, then do not use onCompletion for that.
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onCompletion With Route Scope
The onCompletion DSL allows you to add custom routes/processors when the original Exchange is complete. Camel spin off a copy of the Exchange and routes it in a separate thread, kinda like a Wire Tap. This allows the original thread to continue while the onCompletion route is running concurrently. We decided for this model as we did not want the onCompletion route to interfere with the original route.
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You can only have one onCompletion clause per route. At context scoped level it's possible to have many. And notice that when you use a route scoped onCompletion then any context scoped are disabled for that given route.
Wiki Markup onCompletion will be triggered when the Exchange is complete and regardless if the Exchange completed with success or with an failure (such as an Exception was thrown). You can limit the trigger to only occur onCompleteOnly or by onFailureOnly as shown below:Wiki Markup onCompletion Exchange as Camel will add the property Exchange.ON_COMPLETION with a boolean value of true when it spin offs the onCompletion Exchange.
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The onCompletion is defined like this with Spring DSL:Wiki Markup onCompleteOnly and onFailureOnly is defined as a boolean attribute on the <onCompletion> tag so the failure example would be:Wiki Markup
onCompletion With Global Scope
This works just like the route scope except from the fact that they are defined globally. An example below:Wiki Markup
Using onCompletion from Spring DSL
This works just like the route scope except from the fact that they are defined globally. An example below:Wiki Markup
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If an onCompletion is defined in a route, it overrides all global scoped and thus its only the route scoped that are used. The globally scoped ones are never used.
Using onCompletion with onWhen Predicate
As other DSL in Camel you can attach a Predicate to the onCompletion so it only triggers in certain conditions, when the predicate matches. For example to only trigger if the message body contains the word Hello we can do like:Wiki Markup
Using onCompletion With or Without a Threadpool
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onCompletion will from Camel 2.14: not use thread pool by default. To use thread pool then either set a executorService or set parallelProcessing to true.
For example in Java DSL:
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And in XML DSL:
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You can also refer to a specific thread pool to be used, using the executorServiceRef option:
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Using onCompletion to Run Before Route Consumer Sends Back Response to Callee
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For example to always add a "created by" header you use modeBeforeConsumer() as shown below:
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And in XML DSL you set the mode attribute to BeforeConsumer:
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See Also
- Unit of Work