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Let's look at some legacy code, and spot the problems.
The code to this project can be found on GitHub.
Changes are made to the live branch.
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[MUSIC]
0:00
Now, I realize that this
might cause some trauma.
0:04
But work with me here.
0:08
So imagine, if you will, that this code
here to connect to our legacy database
0:10
is repeated hundreds of times.
0:15
Every single time we need
to connect the database
0:17
this same code dance happens over and
over.
0:20
And it's a bit of a hassle.
0:23
So let's take a look at it really quick.
0:25
So we get a database and then we open
up a try block because this connection
0:26
could definitely throw an IO exception,
and
0:31
sometimes this connection for
some reason it comes back closed.
0:34
So what we've done as a team is we've
made sure that everybody knows that,
0:38
hey make sure that the connection
is open before you do it.
0:42
So it's become part of our dance,
it's become part of our ritual,
0:46
we need to do this.
0:48
So we open it up then we go ahead and
we execute and we get some stuff back.
0:50
This is kind of really the meat of what
the whole thing is trying to do, but
0:54
look at all this code surrounding it.
0:57
So we're going to catch that exception,
right,
0:59
because maybe this connection opens up and
it doesn't work or whatever.
1:01
So we want to catch that, we need
to catch it because it throws that.
1:05
And then finally we need to make
sure that we clean up, right?
1:07
We don't want to leave these
things dangling out there but
1:10
there's a problem there too, right?
1:13
So the cleanUp also might
throw an IO exception.
1:14
Now this is a pretty intense stance and
because it's so
1:17
intense and there's all these places
where it might happen, we've copied and
1:21
pasted this all over our code base.
1:24
It's nobody's fault really because
they were told this is the dance
1:26
that we need to do.
1:29
So let's go ahead and let's run it and
let's just see what happens.
1:30
Now I have gone ahead and
I mocked all the stuff out.
1:32
So basically,
I let us know when things are happening.
1:36
So we know the new database was called,
the connection was opened.
1:39
Then we run our query and then we call
cleanUp which closes the connection.
1:42
So that's what this cleanUp method here
does is it kind of closes the connection
1:46
that, any connection that was open.
1:49
So let's take a look really
quick at our legacy database.
1:51
That's interesting,
it implements AutoCloseable.
1:57
Now this is part of,
Java 7 did this really cool feature so
1:59
that you could kind of help resources that
need to be closed afterwards can do this.
2:03
Now I notice that ours is not using
this try with resources block,
2:07
it's still doing this this finally move
here so let's go ahead and let's fix this.
2:12
Now what I want to point
out here is that we evolved
2:18
our legacy database here to meet the Java
7 standards, but people aren't using it,
2:22
people are copying and pasting and that's
because it's still a bit of a dance.
2:26
Let's go ahead and I'm gonna make this,
so the try with resources block,
2:29
you open it up like this.
2:34
And then go ahead and put that in there
and we're going to lose our finally here.
2:35
I'm gonna go ahead and, we need to
catch an exception now though, right?
2:42
Cuz the autocloseable will
throw an exception so.
2:47
This is kind of what we look like here.
2:53
Actually, guess we can probably
lose this catch, right?
2:56
And we'll just catch any sort
of exception that comes through.
2:59
All right so, what happens is
anything that's inside of this,
3:03
this try with resources,
now it will automatically close.
3:05
Now this is still a dance, right?
3:08
We still need to, we're still making
sure this connection is open.
3:10
We're still going through here.
3:13
We could say, hey everybody on staff,
look, this is how you do it now.
3:15
Don't worry about that finally block
anymore now that we have this try with
3:20
resources.
3:23
But I really think there's a lot
of code that's duplicated here.
3:24
Now, not only is the code duplicated and
that's a problem,
3:28
that you're typing these things over and
over again and you're doing the copy and
3:31
pasta, basically you're just copying and
pasting this, right?
3:34
Let's be honest, you're copying and
pasting this block of code and
3:37
people are copying and
pasting the older block of code.
3:39
So it's hard to shift everybody's
mind to the new way of doing things.
3:41
This is pretty much better,
it's not the best, right?
3:45
One of the things that's really horrible
is that innovation has stalled right?
3:50
Like let's say that we wanted
to do connection pools, right?
3:53
It'd be kind of hard to do that
in each one of these patterns,
3:56
right, you'd have to change the way
that this getConnection comes out here.
3:59
What if we wanted to do transactions,
right,
4:03
like let's make sure that you only want
to have this happen if it was successful.
4:05
That'd be really hard to
do because of this dance,
4:09
is there a better way to do this?
4:12
There is, let's take a look at consumers.
4:14
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