Utilizing Maven Plugins: Jetty plugin

The problem: You would like to use a non-standard Maven plugin, such as the Jetty plugin.

The solution: First things first you will probably need to register the plugins group, so that Maven will know where to look. To do this you should put an entry in your settings.xml file. For our example here we will use the Jetty plugin. It has a group id of 'org.mortbay.jetty'. In your settings.xml file put an entry such as:

<pluginGroups>
  <pluginGroup>org.mortbay.jetty</pluginGroup>
</pluginGroups>

What this little piece of configuration does is tell Maven to search for plugins registered under the given group id. You can have as many 'pluginGroup' elements in your xml file as you want/need. In all my work with Maven I have only actually registered two plugin groups, one of which is Jetty... but if you create your own you will need to register your plugin group.

Lets start by creating a web application using a Maven archetype:

mvn archetype:create -DgroupId=com.mycompany.app -DartifactId=my-webapp -DarchetypeArtifactId=maven-archetype-webapp

This will create a folder called 'my-webapp'. Change over to this directory. Now we are going to use the long way of specifying the plugin. This is ugly and you certainly will not want to use this form often (likely ever).

mvn org.mortbay.jetty:maven-jetty-plugin:run

You should now be able to hit your web app on http://localhost:8080. The above command could be broken down as 'mvn groupId:artifactId:goal'. More on this in a bit. Now lets run the same 'run' goal using a short command syntax. Here is a simpler way to do the same thing:

mvn jetty:run

Much easier. Now I'll explain a bit. Since we put the plugin group entry in our settings.xml file we do not need to specify it like we did in the long command above. In the long command, after the group id, we have 'maven-jetty-plugin'. Maven expects the artifact id to be in a form 'maven--plugin'. For the Jetty plugin the artifact id is 'maven-jetty-plugin'. In the part after the colon in the long command we specify this artifact id. Now in the simple version we just have 'jetty'. Maven will take the 'jetty' value and automatically know to look for 'maven-jetty-plugin'. This saves you from typing out the whole shebang.

If your are interested in creating your own plugin I suggest you check this link out. It is not nearly as hard as you may imagine.

Exercise: Continuum

Today's article is going to be a step by step on getting a pretty hefty Maven based project up and running on your machine. I will finish by having the project set up in Eclipse of better development. The project is Continuum. It is a continuous integration server created by the Maven community.

We will start by checking out Continuum. Use this command to get the project from Subversion:

svn checkout http://svn.apache.org/repos/asf/maven/continuum/trunk/ continuum

Once you have the project downloaded 'cd' on over into it. Do a ls or dir command. You will now find you are looking at a multi-module Maven project! Egads thats a different sight in comparison to a non-multi-module project. Well lets kick things off by running:

mvn install -Dmaven.test.skip

We don't want to test, for now. You will need to run install so that each module's artifact (jar) gets put into your local repo. This is important because a module can rely on artifacts created by other modules, and so the artifacts must be available via repo. This will take a bit, Continuum is fairly big. Once things are done you will want to prep Continuum for Eclipse. Run the command:

mvn eclipse:eclipse

This will go into each module and create the Eclipse meta files, so that you can import them into Eclipse no problems.

We now are at the last step. Open up Eclipse, right click in the 'package manager' view (window). Select 'import'. This pops up a window, select 'general > existing projects into workspace'. Point to the folder containing all the modules and click ok. You will notice Eclipse finds a project for each module. Click ok. After a bit of grunting Eclipse will present you will a view full of projects, one for each module.

At this point you may need one last thing. If you do not have the M2_REPO Eclipse you will need to set it. Check the 'problems' view, if you see a bunch of messages about this not being set... bingo. Go into preferences then "java > build path > classpath" and add the var, giving it a value of the location of your local repo. Mine is "/home/ottaway/.m2/repository".