In my
previous blog post, I listed some of the variables available in Apache Camel’s Simple expression language in Cloud Integration. I didn't go into the details of the
camelContext variable, though, because I felt it deserved a post of its own. This variable is a reference to an object implementing the
CamelContext interface, which lets you access a ton of interesting runtime information.
In this blog post, I will do a bit of exploring around the
CamelContext. So, where to start? First off, let’s find out which class implements the interface:
${camelContext.getClass.getName}
It turns out the implementing class is
org.apache.camel.blueprint.BlueprintCamelContext. Interesting, but what else can we learn? I’d like to know the version number of the underlying Apache Camel framework, and the
getVersion() method returns just that. Let’s try it out:
${camelContext.getVersion}
At the time of writing, the method returns
2.16.2-sap-16, which indicates that this is an SAP variation on the Camel 2.16.2 release. However, just a few days ago, the version number was 2.16.2-sap-15. This is cloud software, after all, and as such, it is updated continuously behind the scenes.
Incidentally, the version number also explains why some features of the Simple expression language are not available in Cloud Integration at the moment, like for instance the
messageHistory variable and the
starts with operator: They were introduced in later versions of Camel (2.17 and 2.17.1, respectively).
Browsing through the API documentation of the
CamelContext interface, another method looks promising:
getUptime(). Let’s give it a go:
${camelContext.getUptime}
Shortly after deploying, the expression evaluated to
39.147 seconds. After making a nice cup of tea, it now evaluates to
7 minutes. The
getUptime() method returns the human readable uptime of the context, i.e. the time that has passed since the integration flow was deployed.
The
getUuidGenerator() method also looks interesting. According to the API documentation, it returns an object implementing the
UuidGenerator interface. This interface has a single method,
generateUuid(), which, to no one’s surprise, generates a UUID. Let’s try to do that now:
${camelContext.getUuidGenerator.generateUuid}
Lo and behold, the expression evaluates to a UUID, that is identical in structure to the message and exchange IDs in Cloud Integration.
Ok, I’ll briefly talk about one more method, and then I will leave you to continue exploring on your own:
getStatus(). This method returns a
ServiceStatus enum, indicating the state of the
CamelContext (starting, started, stopping etc). Let’s check my current status:
${camelContext.getStatus}
The expression evaluates to
Started, which sounds about right to me.
Okay, that’s it for now. Have you discovered other cool stuff, that can be done with the
camelContext variable? Feel free to share it in the comments below.
