Creating a simple application in Open Daylight Controller

In this post I am going to make a simple application in ODL. Main aim of this application will be just to say "I have started" at the time of loading and "Over and out", when it stops.
To program for ODL you need to know java language and Maven, OSGi. Dont panic if you don't know about the last two its fairly easy and I will go step-by-step on that.
When you start developing your folder structure should be as below;

ubuntu@ubuntu:userinfo$ ls
META-INF pom.xml src target 

Here src is where you will have code; target is where you will have binaries META-INF has information related to OSGi (Explained later). You need not to worry about it right now Maven will take care of it.

To understand about OSGi and create a simple java code click here
To understand and create a simple pom file in ODL click here

Once you have build successfully go to your target directory. you will find samples.userinfo-0.4.0-SNAPSHOT.jar over there. Thats your bundle !

Now follow the steps at running a custom bundle and see your sample app running in controller.
If you have any queries feel free to post it :)

Basic pom.xml file for building a bundle in Open DayLight

Maven is something like makefile in linux. Maven helps in compilation. when you say 'mvn install' it reads the pom.xml file. pom.xml have various tags essential tags for creating basic pom.xml are as below. Please note i have put comments between <!-- --> which is standard xml comment tag.
pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

<!-- Do not change above lines. They provide xml version and maven version info -->

    <parent>

<!-- Everything inside this tab is your parents, i.e on top of which you will make your application   --> 

    <groupId>org.opendaylight.controller</groupId>

    <!-- its the project where your parent is located-->

    <artifactId>commons.opendaylight</artifactId>

    <!-- Parent application name-->

    <version>1.4.0-SNAPSHOT</version>

    <!-- Parents version-->

    <relativePath>../../commons/opendaylight</relativePath>

    <!-- Path where parent pom file is located-->

  </parent>

  <scm>

    <connection>scm:git:ssh://git.opendaylight.org:29418/controller.git</connection>

    <developerConnection>scm:git:ssh://git.opendaylight.org:29418/controller.git</developerConnection>

    <url>https://wiki.opendaylight.org/view/OpenDaylight_Controller:Main</url>

  </scm>

    <!-- Everything inside scm tag is for version controlling you can delete this tag if you want-->

  <artifactId>samples.userinfo</artifactId>

  <!-- this is your application name.  -->

  <version>0.0.1-SNAPSHOT</version>

  <!-- Your application version.  -->

  <packaging>bundle</packaging>

  <!-- Tells maven you want to create OSGi bundle.   -->

  <build>

  <!-- Information on how to build the code-->

    <plugins>

      <plugin>

      <!-- Info on which plugin to use from maven   -->

        <groupId>org.apache.felix</groupId>

        <!-- Project name for that plugin-->

        <artifactId>maven-bundle-plugin</artifactId>

        <!-- Kind of obvious we are making an OSGi bundle-->

        <version>2.3.6</version>

        <!-- Plugins option-->

        <extensions>true</extensions>

        <!-- Use extension for this project-->

        <configuration>

          <instructions>

            <Import-Package>

              org.opendaylight.controller.sal.core,

              org.slf4j,

            </Import-Package>

            <!-- Which package to import for building the code-->

            <Export-Package>

              org.opendaylight.controller.samples.userinfo

            </Export-Package>

          <!-- Name of the package, which will be exported-->

            <Bundle-Activator>

              org.opendaylight.controller.samples.userinfo.internal.Activator

            </Bundle-Activator>

           <!-- Address where OSGi activator is located -->

          </instructions>

          <manifestLocation>${project.basedir}/META-INF</manifestLocation>

           <!-- Address of OSGi META file -->

        </configuration>

      </plugin>

    </plugins>

  </build>

  <dependencies>
  <!-- Dependencies on exiting code>
    <dependency>
      <groupId>org.opendaylight.controller</groupId>
      <artifactId>sal</artifactId>
      <version>0.5.0-SNAPSHOT</version>
    </dependency>
  </dependencies>

</project>

For more information on how to make a simple application in open daylight controller click here