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Let's learn what to do when you have the awesome problem of too much data. We'll also explore custom search queries.
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Okay, so we have a good problem, right?
0:00
We have way too much data.
0:02
Now a typical solution to this is
that I introduced paged results and
0:04
guess what, it's super easy to do.
0:08
So let's pop over to the CourseRepository.
0:11
Now remember this is what's
generating our controllers, right.
0:14
So let's pop over here, and
if we simply change this from
0:16
CrudRepository to
PagingandSortingRepository.
0:21
And then, let's also do that for reviews
while we're in here because we're probably
0:28
gonna have a lot of these too,
at least hopefully, right?
0:31
And if we swing down here and
we reboot our server, I'm gonna ahead and
0:33
click this Reboot button.
0:38
Let's let this go.
0:44
Awesome, so now if we flip over back to
our courses page, if I refresh this, if
0:47
we scroll down, we will see that there is
a lot of new things here at the bottom.
0:52
Namely first, right?
0:58
So this is the first page and
there's only 20.
1:00
So right, so there's only 20 on this page.
1:02
It still kind of seems like a lot but
there's only 20 and
1:04
it shows the next page which is page 1 and
it shows the last page.
1:06
Pretty cool, right?
1:11
Now let's think about this for
a minute, what if the users of our API,
1:12
like our other teams, what if they were
trying to add a feature to find all
1:15
the courses with a certain word in it?
1:19
I guess what they'd have to do now right
is search through each of these pages.
1:21
That'd be a bummer, right?
1:24
Well again, no surprise.
1:26
This can just happen.
1:28
Okay, so let me show you.
1:30
So, if you head over back
to your course repository,
1:31
we can just add a new query here, right?
1:35
And if we use the standard
naming conventions,
1:37
our query will just be exposed.
1:41
So what do we say we wanted?
1:43
Right.
1:45
Let's say that we wanted to find all
the courses with a certain word in
1:46
their title.
1:49
So to do that, what we'll do is we'll add
a method that returns a page of courses.
1:50
And the proper naming thing,
we're gonna say, findByTitleContaining.
1:57
You probably remember this from spring
data, findByTitle containing, right.
2:03
And we're gonna pass in
the parameter of title,
2:08
parameter of a named query param there.
2:12
And it's going to be the title.
2:15
And then finally we're
gonna pass in an iterator.
2:17
It will get an interior.
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Expect an iterator.
2:26
Okay.
2:28
Give us some more space there.
2:30
There we go.
So,
2:32
again a special name
findByTitleContaining,
2:32
title being the field.
2:35
And we're gonna say,
call it title when it comes across.
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Watch this.
2:40
So, we're gonna restart and
refresh the course.
2:41
Pop up over here.
If we take a look and
2:50
we go again down all the way to the
bottom, we'll see here that there's this
2:51
new search item that's available, so
that says that we can search on courses.
2:56
So let's bring that up and
3:00
again it's just added that automatically
because we have something there.
3:02
And now there's a thing called
findByTitleContaining and
3:05
it shows you what you can do here,
what parameters it takes.
3:09
This is a templated, right, so
this is a templated search.
3:12
So we're gonna go ahead and let's do this,
let's say findByTitleContaining.
3:14
And the query parameter that we're gonna
pass is title and we want it to start with
3:21
something, whatever, let's say,
Java lets see what, what comes up.
3:26
Here is all of the Java reports,
look at that?
3:29
Looks like our database loader has
the same number of things, I'm assuming.
3:40
So let's add one more on here.
3:47
And let's say we wanna
learn about spring HATEOAS.
3:50
So let's refresh this.
3:57
That will happen if you're generating
data and they have the same.
4:00
So the trick that kind of isn't working
for the the different modelos there.
4:02
So we rebooted this.
4:06
Let's go ahead and look again for
everything containing java.
4:07
There we go.
4:11
See that the titles are different now.
4:12
Java 9, different course numbers.
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There we go.
4:16
And also look, it's still paged, right?
4:19
So we know that there's only 18 on this.
4:22
There's only 1 page.
4:24
But isn't that cool?
4:26
It's still paged.
4:27
Search results, so what if we didn't
like this findByTitleContaining?
4:28
What if that seems a little bit
awkward to use in a REST world?
4:32
So one thing that you can do, and you can
do this actually with just about anything
4:35
that gets generated over here, is we
can change what this is displayed as.
4:41
So if we use the annotation RestResource,
we can say that the rel, you
4:46
know this is what the the link is called
in the search there, that's available.
4:52
Since we're on a search here.
4:57
I'm sorry,
back here in the search page here.
5:00
We'll see that this is the REL here,
findByTitleContaining.
5:05
So we can change that
to be title-contains.
5:08
And we can also even
change the path to it.
5:11
So let's make that read,
let's say instead of find,
5:14
let's have it be called containsTitle.
5:17
That should be clear, right?
5:19
So again, if we refresh
5:22
Come over here, you'll see that it's now
called title-contains and is looking for
5:31
contains-title as the link.
5:35
Pretty cool, right?
5:36
For more on these powerful search queries,
see the teacher's notes.
5:37
Now, side note here too is that this
rest resource little name that we did,
5:40
on the course repository.
5:45
We can also change this up here.
5:47
So you could change what the default
pluralization of the route.
5:49
Now you can also change the global paging
size with a simple configuration change.
5:53
Let me show you this.
5:57
It's a pretty common
stack overflow request.
5:58
So first remember that spring
boot looks specifically for
6:00
property files in the class path.
6:03
So if we come over here and we make a new
file In the resources root new file and
6:06
we call it application.properties.
6:13
We can set different configuration things.
6:18
So let's say that we find that our
team wants to only show five of these
6:20
courses on a page at a time or
reviews too and
6:23
they keep specifying a different size
in the URL, we don't wanna make them
6:26
do that what we really wanna always have
the default page size to be 5, right?
6:30
So you do
spring.data.rest.default-page-size.
6:34
And now, by default it was 20, right?
6:41
We were seeing 20 on the page.
6:43
What if we say 5?
6:44
So we'll just do equals 5, and
then if we come back over to our
6:45
All right, PI over here.
6:55
If you just look at courses,
you'll see that there are only 5.
6:57
And now it shows that
the last page is page 20.
7:03
There's 20 pages of fun.
7:05
Awesome, right?
7:07
We'll go over a few more of the options
that you can tweak in here and
7:08
I've included the link
in the teacher's notes.
7:10
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