- Getting Started 5:55
- Introducing Spring Data REST 6:03
- Entities and Repositories Review 9:28
- Abstract Classes 6:48
- Populating and Relationships 15:39
- Paging 7:12
- Exploring Your API With New Tools - Postman 7:55
- Exploring Your API With New Tools - HAL Browser 3:58
- Versioning 8:52
- Validation 8:31
- Adding Users 11:51
- Adding Authentication 10:35
- Authorizing Deletions 6:56
- Events 7:57
- Wrapping Up 1:18
Preview
Video Player
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00:00
Events
7:57Let's automatically set the reviewer on the creation of new reviewers to the logged in users. We will use an annotated event handler to capture the BeforeCreateEvent.
So we have a nicety that
we'd like to add to our API.
0:00
We want the creator of
the review resource to be set
0:03
as the reviewer when it's created.
0:06
This idea of running certain code at
certain times is pretty common request.
0:09
As you can imagine it's usually
where the business logic lives and
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since all the controller code is
currently tucked away out of sight,
0:16
it might be a little confusing as to
where we should add logic like this.
0:19
Well the good news is that this
problem has been thought about and
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it has been solved for you.
0:26
Probably, there are eight events
that the spring data rest emits.
0:27
These are pretty self-explanatory and
0:31
knowing what you can hook into that
will probably make you feel a lot more
0:33
comfortable about not having
access to those controllers.
0:37
This is usually where you'd
write any custom logic, right?
0:40
So we want to set the reviewer
before things are created.
0:44
So we'll use the before create event.
0:47
Let's do this.
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There are a few ways to register events.
0:51
If you wanna capture all entity creation
you can write an application listener.
0:53
But in our example we're really only
concerned with when reviews are created.
0:56
What we're going to do is
write an annotated handler.
1:01
Which we can restrict to
a review entity specifically.
1:04
So in our review package, let's make
a new class named ReviewEventHandler.
1:07
New Java class ReviewEventHandler.
1:16
Okay and now we'll annotate that
with RepositoryEventHandler.
1:24
And with that does is
that takes a class and
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it's whatever we're interested in watching
which remember that's Review.class.
1:37
So the way that these work is you
define what it is that you're
1:41
trying to do in a descriptive method,
right.
1:44
So let's go ahead and let's say.
1:46
We're trying to do is we're trying to
add the reviewer as it goes, right.
1:49
So let's say public void
addReviewerBasedOnLoggedInUser.
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It can be as descriptive as you want.
1:59
So we'll say review review and
we want this to happen before, right?
2:01
So we're going to do handle before create.
2:09
So having these as separate methods is
pretty nice because each of them are right
2:17
for unit testing right.
2:22
Okay so let's inject our user repository
so we can get stuff out of it, so
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we'll say private final UserRepository,
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so users, and
I'm gonna go ahead and allow this.
2:33
With this automatically add
a constructor parameter and
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then we'll mark our
constructor here as auto wired.
2:43
And because we need to have this
picked up by a component scan,
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we need to mark it as a component.
2:53
And now let's work our magic.
2:56
So, to get the currently long
in user you do this incantation.
2:58
So let's say get user name and
that's from security ContextHolder
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has a getContext, I'll go ahead and
give us some space.
3:10
Has a getContext, and
then it has a getAuthentication,
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and then it has a getName.
3:22
Note that we're going to get a null
pointer exception here if they aren't
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authenticated.
3:28
But alas, they should be so
we'll go grab our user.
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So we'll say user user =
users.findByUserName and
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we'll pass in that username.
3:40
And finally,
we'll just set it on the reviewer and
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the review will say
setReviewer[user] makes sense right?
3:54
Before things are created, okay?
3:59
I will go and reboot our server here.
4:00
Let's see, let's grab somebody
over here to make a review for,
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let's see, let's grab Seth Kroger.
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He is an amazing moderator for us so
let's write an appropriate one for him.
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So we're going to make this a post and
we're going to erase this one and
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we're gonna go to the authorization
we're gonna log in actually as Seth,
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he's got the same password
which is password.
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Seth change that,
say update request, okay.
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And if we come over here to the body,
this is actually a review.
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So what we wanna do is we're
gonna have him give us
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a little bit of a harsh rating.
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Let's say the rating.
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Let's do the course first.
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So "course" and
now again we've moved this.
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So it's "/api/v1 Courses one so
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basics and
we're going to give a rating of two.
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That's pretty harsh stuff,
which what, what's he upset about?
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What is Seth upset about?
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Let's see.
5:07
So for the description come here and
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say why why did you use
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system.io.console.
5:22
Well that's a lot isolation points so
I have to calm down.
5:27
Do you know how many
times I've had to answer
5:30
why this doesn't work in the clip.
5:36
I totally made that up, that's
something Seth would never ever say.
5:41
He's one of those amazing moderators
that makes everyone feel so
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comfortable in the community and thanks
for keeping something so positive and
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being so patient that the students and
I really appreciate it.
5:51
Okay let's see if this works.
5:54
So we have not set the reviewer,
but Seth is logged in, and
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we're going to click send.
6:00
Here we go.
We got a bad request because,
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why did we get bad request?
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No suitable found to read
the request body to object.
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Do I have a weird header?
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I did not set this.
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I said it as text that
something good to know, right.
6:21
So doesn't know it says and
it says right here.
6:23
Can't do with the content type plaintext,
right?
6:25
Let's switch this over to my
application JSON and they set there.
6:27
Maybe that will be an answer for
this one isn't better there in the video.
6:33
So that's maybe one you
don't have to answer.
6:36
Boom, there it is and
here comes Seth Kroger coming across.
6:39
So as you can imagine, we could do all
sorts of other handling in these events,
6:43
including sending notifications,
updating caches, some advance validation.
6:46
But whatever business logic you
can dream up you can put in there.
6:51
Now one thing to always remember here
though is that this action is synchronous
6:54
meaning that it's in the request response
loop so users will be waiting for
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this code here to execute.
7:02
So don't do anything too intense In here.
7:04
Awesome, right?
7:07
I know when I was first looking
at the spring data rest project
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I was not very trusting.
7:11
I was like,
yeah sure I guess we do duplicate
7:13
a lot of code when we write APIs.
7:16
But where's all the business logic code?
7:17
Events are where you can inject that.
7:20
I've also found that these methods
make unit testing your business logic
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simple and quick.
7:25
Speaking of testing,
it's outside the scope of this workshop.
7:27
But I do beg you to remember that
you don't need to test what has
7:30
already been tested by framework creator.
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Remember your boundaries.
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Test only what is your responsibility and
what could actually break.
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I suggest you test your validation,
your security, and
7:41
that your custom events
are working as you intended.
7:43
But please don't go and
test status codes and
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error message that you haven't customized.
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Find the right balance, and
remember to not test what has been so
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graciously abstracted away for you.
7:54