Getting Started With Apache Camel Part 1
Getting Started With Apache Camel Part 1
Looking to get up and running with Apache Camel? Have a look how to start a basic Camel project and what tools are available.
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Apache Camel is an open-source software integration framework implementing the patterns described in the Enterprise Integration Patterns book.
The detailed description of the framework can be found on its official website.
In this tutorial, we will have a look how to start a basic Camel project and what tools are available.
Creating a Basic Apache Camel Project
There are multiple ways of starting a new project using Apache Camel. We will first start with the simplest possible empty Java project and add Camel as a dependency. To do that, first we need to execute the following command:
The above command will generate an empty Java application using the
maven-archetype-quickstart Maven archetype.
The first thing we need to do is adding the Apache Camel library to the pom.xml dependencies file. It should look as follows:
I will also require a camel.version variable to be defined in the properties section of the pom.xml file, like so:
Altogether, the file should look like the following:
At this point, the directory structure should look like this:
Creating Camel Context
Camel context provides the runtime environment for the whole Apache Camel application. Usually, we will create one context per application and all Camel routes will be executed within the context.
We will set up a simple application where the context will be started when we run the application. After that we will let the context run for couple of seconds and then we will shut it down - this is not what you would do normally in the production environment, but we can have it as such to be able to play around with it.
We will open the App.jave file and modify it to look as follows:
Most notable thing happening above are:
1. Importing packages which will be used
2. Creating a default Camel context:
3. Adding a route to the context:
4. Starting and stopping the context:
Camel context implements a Java Service lifecycle interface so it has
stop() methods. In addition to that, it implements
resume() methods so it is convenient and easy to manage the context lifecycle. From the Apache Camel official website:
The operations is paired: start/stop and suspend/resume.
Stop is performing a Graceful shutdown which means all its internal state, cache, etc is cleared. And the routes is being stopped in a graceful manner to ensure messages are given time to complete. If you start a
CamelContextafter a stop, then its performing a cold start, recreating all the state, cache etc. again.
Also, worth mentioning is the route itself. In the example above, we have created a very simple route which will take the contents of the
in.csv file from the current directory and copy all the contents for the
out.csv file in the same directory. The
noop=true parameter tells Camel not to do anything with the file. Without this option Camel would move the the file into
.camel directory after processing it.
We can now build, and run the application to see it working. First, we need to create some dummy data and put it in the
in.csv file (the content of the file does not matter at this moment).
When that's done we can execute the application with the following Maven command:
We should see the standard maven output followed by the following:
Also if we list the current directory now we should see a new file called
out.csv with the same contents that were put inside the
In the article we explored how to build and run a simple, basic application using Apache Camel.
There are multiple other ways to start a Camel application from scratch (eg. using the Maven Camel archetype or Camel Spring Boot archetype) but the purpose of this article was to show how to build Camel application from ground up without using automatically generated code so that it is more understandable how are all the components wired together and how the Camel application works.
Published at DZone with permission of Krzysztof Kaczmarczyk . See the original article here.
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