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Getting Started With Apache Camel Part 1

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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.

· Integration Zone ·
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Introduction

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:

Shell


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:

XML


I will also require a camel.version variable to be defined in the properties section of the pom.xml file, like so:

XML


Altogether, the file should look like the following:

XML


At this point, the directory structure should look like this:

Shell


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:

Java


Most notable thing happening above are:

1. Importing packages which will be used

Java


2. Creating a default Camel context:

Java


3. Adding a route to the context:

Java


4. Starting and stopping the context:

Java


Camel context implements a Java Service lifecycle interface so it has  start()  and  stop()  methods. In addition to that, it implements  suspend()  and  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 CamelContext after 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:

Shell


We should see the standard maven output followed by the following:

Shell


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.csv  file.

Summary

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.

Topics:
apache camel, apache maven, java, tutorial

Published at DZone with permission of Krzysztof Kaczmarczyk . See the original article here.

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