Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll
Well done!
You have completed Intro to Java Web Development with Spark!
You have completed Intro to Java Web Development with Spark!
Preview
Let’s use the Data Access Objects pattern to build an interface that you can use to store your data. You will not be connecting to a database in this course, but this is one way to ensure that your code will work when you do.
Learn more:
- The Spark site has some great tutorials. Here is one on using sql2o with Spark which will get you up and running with a database.
- Data Access Object Pattern and a pretty good tutorial on them.
- Check out our Hibernate Basics Course!
Related Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign upRelated Discussions
Have questions about this video? Start a discussion with the community and Treehouse staff.
Sign up
[NOISE] So
let's keep moving on our project.
0:00
I find that working on the model is
a great way to shake out a prototype.
0:06
So let's think through our problem a bit.
0:11
We obviously need to have an idea,
which has a title.
0:13
And the idea'll also have a creator.
0:17
Now, we'll worry about how to
keep track of votes in a bit.
0:19
First, let's create the ability to
add ideas and then retrieve them.
0:22
Now, to me, that sounds like we
need to store things somewhere.
0:25
I mean, what we wanna do is make it so
that even if our web server restarts,
0:29
that our data is saved someplace,
or persistent.
0:34
That's a little out of scope for
this project, though, so
0:37
check the teacher's notes for more info.
0:40
So let's do this.
0:42
Let's use an interface and
0:43
we'll build a prototype implementation
that just uses normal data structures.
0:44
Sound good?
0:48
That way, later we can swap out
a database implementation or
0:49
anything for that matter.
0:53
As long as it meets our contract,
we'll be good to go.
0:53
That seems like a pretty light way to
do things in its micro framework land.
0:57
Now, larger frameworks provide some of
this capability out of the box, but our
1:01
micro framework here doesn't necessarily
force us into any direction at all.
1:05
So what do you say we drop that contract.
1:09
So let's make a new class.
1:13
And we're gonna put it in a new package.
1:17
So we're gonna say model.Courseidea.
1:19
And this is where we will store
the data structure basically.
1:28
So we said that this is gonna have
a string [BLANK AUDIO] called title,
1:32
and we also said it's gonna have
a private string called creator.
1:39
So let's go ahead and we'll generate,
remember that was Cmd+N,
1:45
we're gonna generate the constructor.
1:50
And then, we'll take both of those.
1:54
Title and creator and while we're at it,
let's do another generation.
1:57
Let's generate some getters.
2:01
And while we're here, let's go ahead and
let's generate the equals and hashCode.
2:10
I'll just use the default one.
2:16
Great.
2:20
Made you type all that stuff out?
2:22
Sorry about that.
2:25
Now, the simplest way to get where we're
headed is to have a single interface that
2:26
accesses all we need data storage wise.
2:31
So let's build it and we'll talk about it.
2:34
So a commonly recognized way of naming
the way that you plan to access the data
2:36
is with the acronym DAO,
or Data Access Object.
2:40
This is a design pattern that's used
to abstract a way how you retrieve and
2:46
store data.
2:49
Check the teacher's notes for
more on this.
2:50
So what we wanna do is in our new model,
here,
2:52
we wanna make a new Java Class and
we're gonna change it to be an Interface.
2:55
And what we're gonna make that
3:01
called is the CourseIdeaDAO,
3:06
Data Access Object.
3:11
So all we really need for
this is a way to add new ideas.
3:14
So we wanna make something called add and
it will take a CourseIdea,
3:21
called an idea, and then we also
need to have a way to find them.
3:28
So let's do that.
3:33
Let's make a list of CourseIdeas
3:34
and it's returned from a method
that's called findAll.
3:40
Now note, because this is the interface,
3:43
we aren't writing any
of the implementation.
3:45
We're gonna do that now, so
let's add our silly implementation.
3:47
So let's make a new class
in this model here.
3:53
Make a new Java Class and we're going
to call it SimpleCourseIdeaDAO.
3:57
Now, i'm calling it simple just to make
sure that we remember that this is
4:04
a simple way of doing things,
this is not how we should actually do it.
4:09
So let's do this.
4:12
And what we want it to do
is wanna implement that
4:14
Data Access Object interface.
4:18
So that's the CourseIdeaDAO.
4:21
Right away,
it's gonna start complaining, and
4:24
it's gonna say that we need to
implement the methods, so let's do it.
4:25
We'll implement both of these guys.
4:29
Then, we're gonna need to have a private
list of ideas that will maintain,
4:35
cuz we're gonna do this all
using normal data structures.
4:41
We're not gonna be using a database.
4:45
So we'll put here, we'll put private
4:48
List<CourseIdea> and
we'll call those ideas.
4:52
And on the constructor, [BLANK AUDIO] we
5:00
will automatically just
create a new ArrayList.
5:05
[INAUDIBLE] So
we'll say ideas = new ArrayList.
5:11
Awesome.
5:20
And it's using the diamond method.
5:22
So now we just kinda do
what we would think.
5:25
So if somebody calls add,
we wanna add our idea to our list.
5:28
And then, just in case somebody tries
to get cheeky and does a findAll and
5:36
appends the list, let's go ahead and
make sure that we make a copy of the list.
5:42
So we're gonna say new ArrayList.
5:47
And remember, collections can take another
collection and it makes a new one from it.
5:51
So this is not actually
a reference to the list.
5:56
It is a brand new list,
so you can't append this.
5:59
You can't do findAll and then do your
own appending to it, make sense?
6:03
And now for
the part that's pretty crazy/cool, ready?
6:08
So we're gonna flip back to the app Main.
6:13
And in here, remember we're
inside of a main method here.
6:17
So let's go ahead and
make our model appear.
6:21
So we're gonna say CourseIdeaDAO,
and we're gonna call that dao.
6:26
So remember,
this CourseIdeaDAO is our Interface.
6:34
And this is our implementation.
6:40
So we're gonna implement
the SimpleCourseIdeaDAO.
6:42
Now, later if we wanted to, we would
switch that out with the database one.
6:44
So any one of these route methods
can now close over this DAO.
6:48
Does that make sense?
6:54
Now, I want to remind you this
should only be used for prototyping.
6:56
Do not do this at home.
7:00
This SimpleCourseIdeaDAO will
not survive a server restart.
7:02
We'll talk about more of it here in a bit.
7:08
But remember it's called simple,
don't do it at home.
7:10
Please, please, please remember
that this is just a prototype.
7:14
Do not run this live.
7:18
That simple CourseIdea,
data access object, is goofy and
7:20
won't survive a server restart.
7:24
You really wanna persist or
save this data for later use.
7:26
And our implementation is
really cutting corners.
7:30
So after we use this a bit, you will for
7:32
sure want to implement a data
based implementation, or
7:34
even a file based implementation, just so
you don't need to keep re-adding things.
7:37
That said though, let's go ahead and
7:42
add the ability to add,
right after this break,
7:44
You need to sign up for Treehouse in order to download course files.
Sign upYou need to sign up for Treehouse in order to set up Workspace
Sign up