The first time you execute this (or any other) command, Maven will need to download all the plugins and related dependencies it needs to fulfill the command. From a clean installation of Maven this can take quite a while (in the output above, it took almost 4 minutes). If you execute the command again, Maven will now have what it needs, so it won’t need to download anything new and will be able to execute the command much more quickly.
As you can see from the output, the compiled classes were placed in ${basedir}/target/classes, which is another standard convention employed by Maven. So, if you’re a keen observer, you’ll notice that by using the standard conventions the POM above is very small and you haven’t had to tell Maven explicitly where any of your sources are or where the output should go. By following the standard Maven conventions you can get a lot done with very little effort! Just as a casual comparison, let’s take a look at what you might have had to do in Ant to accomplish the same thing.
Now, this is simply to compile a single tree of application sources and the Ant script shown is pretty much the same size as the POM shown above. But we’ll see how much more we can do with just that simple POM!
Now you’re successfully compiling your application’s sources and now you’ve got some unit tests that you want to compile and execute (because every programmer always writes and executes their unit tests *nudge nudge wink wink*).
