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It's All About the POM
3:41In Maven, an entire project's configuration can be encapsulated in the file named pom.xml. POM stands for "Project Object Model". This video discusses the high-level details of what most POMs will contain.
Now, that we're gonna be peeking into
files and write any a bit of code,
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it's time to switch to an IDE.
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I'll use IntelliJ IDEA, okay, excellent.
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I'll open this project panel and
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then, I will open palm.xml, there it is.
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As I said in the last video,
POM stands for Project Object Model.
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And this file represents a one stop
configuration for the entire project.
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As you can see, it's an XML
representation of the Maven project.
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The root node of a POM will
be this project element
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followed by the model version element.
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Which for
anything using Maven 2.0 or higher,
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the model version will be 4.0.0, okay?
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Next following this model version is
a group of four elements that define what
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are called the Maven coordinates.
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That's the group ID, artifact ID,
package, and version.
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If you've used other
dependency management tools,
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you've have to reference these
coordinates to use a third party library.
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These categorize and
identify the archive that this POM
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will produce on a repository
like Maven central.
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Let me show you an example of what I mean.
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If we need a third party library,
that helps us examine file metadata,
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like file types and
the dates that they were created.
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We might use the Apache Tika library.
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Now, I can go to search.maven.org and
search for Apache Tika.
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And if I scroll down a bit towards
the bottom of the page, I see tika-core.
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And upon clicking on it,
I will see the group ID,
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the artifact ID and
that version right there.
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And even all the way over to the right,
I see this jar, okay, back to IntelliJ.
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This group ID here is a unique identifier
for a business or organization.
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Usually, in a form similar to Java package
naming, in our case, com.teamtreehouse.
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The artifact ID,
is an identifier unique within the group.
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And helps pinpoint the exact project
within combat team treehouse.
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In our case,
it is file-spy skipping to the version and
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this one is fairly self-explanatory.
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What version of file-spy will
the created artifact represent?
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A quick note on SNAPSHOT,
whenever you see that on an archive,
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that means that this project
is a work in progress.
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It is not a final release, yet.
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Now, speaking of that artifact,
if we backtrack to the packaging element,
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we'll see that ours specifies jar.
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And this packaging element specifies
the kind of archive created by this build.
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When put together, the artifact ID,
version, and packaging
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elements all combined, will represent
the name of the generated archive.
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We will see later on that our archive
will be named file-spy-1.0- snapshot.jar.
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Okay, these next two elements, a name and
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url give the project a nice
reader friendly name.
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As well as a url for
the Maven project itself.
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And following that,
we see this dependencies element.
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In this element,
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we'll specify all the external
libraries that this project depends on.
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There is one in there by default and
that is this junit library.
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We'd want this library if
we were writing unit tests.
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Which in a distributed Java application,
we definitely want to do.
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Okay, let's take a break here before
returning to these dependencies in
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the next video where we'll
start coding our application.
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And in doing so,
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we'll lean on a third party library
that will add to our POM file.
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