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In Java, a POJO is a Plain Old Java Object. In this video we discuss POJOs and our use of them to model our underlying GIF data.
[SOUND] You've been introduced
to the Spring framework and
0:00
you've even created a Web
app that serves Web content.
0:04
That's awesome.
0:09
What I'd like to do now is start
looking at one of the most subtle,
0:12
but powerful features of Spring and
that is its
0:15
ability to let you use plain old Java
objects to control your application.
0:18
What are these Plain Old Java Objects or
POJOs for short?
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A POJO is a Java object
whose class is coded for
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its natural functionality and not for
the framework which it will be used in.
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That means that the class is coded
with fields, constructors, getters and
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setters, and
methods that are useful to the object
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as it fits in with the other
classes of your application.
0:44
Not because of how it fits in with the
framework you've chosen, such as Spring.
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We're going to see this most clearly
in the way we store our GIF data
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into objects.
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What we'll do is write the code
that models or represents a GIF.
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If this phrasing is unfamiliar to you,
think of it this way.
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Since we'll be storing and interacting
with GIFs we should have a sense of
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the kinds of we want to
track about our GIFs.
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We'll include the following
data on our first go around.
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We'll include the name
which will be a String,
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the date uploaded which will
be a local date object,
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the username of the user who uploaded
the GIF which will also be a String.
1:22
And finally, whether or
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not this GIF is marked as a favorite
which will be a Boolean value.
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The class we write to represent each
GIF object is referred to as a model
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because it serves as a model for
the objects we'll create.
1:35
Kind of like a role model serves
as an example of the traits and
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behaviors we'd like to
practice as human beings.
1:42
Well, see this term pop up again when
we discuss the model view controller
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architectural pattern later on.
1:50
Let's go to our first model together,
the GIF class.
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Just so that we can keep all
potential models organized,
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I'm going to create another package
called com.teamtreehouse.giflib.model.
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So I'll right-click on the giflib package.
2:05
New, Package, and I'll call it model.
2:07
That'll be a package side by
side with controller here.
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This is the package into which we would
put all data models, whether we have 1 or
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even 100.
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To create the model,
I'll create a Java class name Gif.
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Right click, New, Java Class, Gif.
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Now, even though Gif is an acronym, notice
that I'm not capitalizing the I or the F.
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We'll reserve the all caps for
class constants.
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In other words, static final fields.
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So I'll click enter to create the class,
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then we have our blank
class ready to code.
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We mentioned four fields
that we'd be adding here.
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Name, date uploaded,
username, and favorite.
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So let's create those now.
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The name I will use a string for.
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The date uploaded, we're going to
use Java 8's LocalDate object.
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dateUploaded.
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The username will be another string.
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And the favorite will be a boolean.
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Wonderful.
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We'll need getters and setters for
each of these fields at this point, so
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let's create them.
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What I'll do is use the Cmd
+ End keyboard shortcut to
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automatically create new methods.
3:18
So I'll arrow down to Getter and
Setter, hit Enter.
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Then, I'll highlight all
the fields by holding Shift and
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arrowing down until they're all selected.
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You could also do this with the mouse.
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Then I'll hit Enter, and just like that,
boom, they're all generated.
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Pretty sweet.
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If you're using Eclipse, Spring Tool
Suite, which is based on Eclipse, or
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even NetBeans, they all have this option
of generating getters and setters.
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It's a huge time saver.
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And hey, let's use another IDE shortcut to
generate a constructor with all fields.
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So I'll put that at the top here.
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Again, I'll use Cmd+N.
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Hit Enter with constructor highlighted,
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then highlight the fields that I want to
include in the constructor as parameters.
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Again, I'll highlight all of them,
and hit Enter.
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And just like that, our constructor's
created just as we want it.
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Much faster than writing
all that code manually.
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And that's all there is to our
model class for a Gif object.
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Pretty straight forward, right?
4:17
Next, we'll look at how to use
the Gif model in our controller
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to pass data to our timely templates.
4:23
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