- What is MVC? 3:10
- Model View Controller Basics 3 questions
- Create a Category Model 1:40
- Fix a Model 1 objective
- Add a CategoryRepository 5:41
- Add a CategoryController 9:40
- Fix a Controller 1 objective
- Code Two More Thymeleaf Templates 4:13
- Fix a Thymeleaf Template 1 objective
- Wrappin' It Up 1:18
- Spring MVC Review 3 questions
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Add a CategoryController
9:40In this video, you are tasked with creating a controller to handle requests related to categories.
With our model and data repository in
place, let's move on to the controller.
0:00
We'll need a controller for categories
that can capture requests to a URI for
0:05
all the categories and
a URI for a single category.
0:09
So, here's your next task.
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Create a Category Controller with one
method [SOUND] that captures requests to
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/categories and returns a String.
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This method should fetch the entire
list of category objects from
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an auto-wired category repository and
add it to a ModelMap.
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[SOUND] Then, the method should return
the string categories to associate it
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with the provided Thymeleaf Template.
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Are you ready for this?
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Okay.
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Go ahead, have at it.
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But wait, remember to use the GIF
controller as an example to follow.
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Ready, set, code.
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>> All right, what you're looking at
here is my category controller class,
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which I put in the controller
package with the other controller.
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You can see that I've annotated the class
with Controller and included an Autowired
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category repository that I can use
in the controller method down here.
1:00
As for this method, I've annotated
it with request mapping to capture
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any requests for the category list page,
which is /categories.
1:09
Here is my modelMap parameter, and
inside is the the call to the repository's
1:14
getALLCategories method that
we wrote together earlier.
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I added the list that was returned
by this method to the modelMap using
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modelmap.put here.
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And here I've returned the name of
the time leave template, or categories.
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This is will ensure that it's
the categories.html template that will be
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rendered when this page is requested.
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The last piece of this controller,
we'll do together.
1:41
We'll need another method that will
capture requests to an individual
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category.
1:46
To start that, I'll request
a mapping to a single category page,
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category/, and
here we're going to use an integer id.
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The name won't work well
as a URI placeholder
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here because names could
have spaces in them.
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So instead,
I'll use the integer id as a placeholder.
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Then we'll start typing the method
public String category.
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And the first parameter I'm going
to list is our @PathVariable.
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That will capture the value
that's passed into
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the id placeholder that's in
our RequestMapping annotation.
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So I will call it id.
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And of course, we'll include
an instance of a modelMap that'll
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be passed in by the Spring framework.
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>> Now, I know I'm going to return
the single categories template,
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which is given in category.html, so
I'll type in that return value right now.
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That's going to be return "category".
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Now I know the category page
in the browser should probably
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contain the category name, as well as
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all GIFs related to that category,
>> So by the time we reach the return
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statement we better have added to
the model map, both a category object
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associated with this ID as well as a list
of GIFs associated with this category.
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Let's tackle each of those now.
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First, the category object.
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You just wrote a findById method, so
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we'll call that now and
add the result to the model map.
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I'll create the category object,
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And use the categoryRepository field and
call its findById method
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passing it the integer id that
came into our path variable.
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Then I'll add the category object that
was returned by the findById method to
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the model, using modelMap.put.
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The name I'll give it will be simply
category, and I'll pass category.
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Whatever value was stored in there
as a result of this return value,
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I will add to the ModelMap.
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Now onto the next item.
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For a list of the GIFs associated with
this category, we'll need to use a GIF
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repository to fetch all those GIFs
within a certain category ID, like this.
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I'll give myself a couple
lines to separate this code.
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And the first thing I'll
do is define a list that'll
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hold that list of GIFs that comes
back from the GIF repository.
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Make sure to import the GIF class there,
since we haven't done that yet.
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And I'll call the gifRepositories,
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findByCategoryId method,
passing it the id.
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And finally, adding that list to
the model map with modelMap.put.
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I'll call that "gifs" in the map key,
and pass it the object gifs.
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But wait,
there are two problems with this.
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First, there is no GIF
repository variable defined.
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And second, there is no
findByCategoryId method defined for
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a GIF repository object.
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The first one we can fix right here.
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We'll simply add an Autowired
gift repository to the object.
5:00
So I'll add that with the @Autowired
annotation, add a GifRepository.
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That fixes the first error, but
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we still have this error with
the missing findByCategoryId method.
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This one will take a bit more work.
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But it's still pretty quick.
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We'll hop over to the GifRepository class,
and add a findByCategoryId method.
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So let's scroll down here and
I'll just add it to the bottom.
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That'll return a list.
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FindByCategoryId, and let's have
it accept a single end parameter.
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So this method, given some int id,
will essentially iterate over our
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list up here looking for
objects that have a given category id.
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If they haven't given a category id,
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I will include those in
the list that I return.
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So to start, we better initialize
a brand new empty list.
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I'll make it a list of GIFs and
initialize it as a new ArrayList.
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Make sure to import those classes,
excellent.
6:18
Now, let's use a for each loop to
iterate over the list of ALL_GIFS.
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So for every Gif,
I keep typing Fig, how about Gif?
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For every Gif in ALL_GIFS Let's
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check to see if the category id of the Gif
object in this iteration of the loop is
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equal to the id value that
was passed in as a parameter.
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So, if gif.getCategoryId ==,
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I can use double equals here.
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It's a primitive value.
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I don't need to use dot equals.
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Then what I want to do
is add that to the list.
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So, by the time we get through this loop,
any Gif in the list that has the category
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ID that was passed in
as a parameter value,
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will be added to the list name Gifs.
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And once I get through my loop,
what I'd like to do is return
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whatever list has resulted
by iterating over all gifs.
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Now that we've coded this method, after
we jumped back to the category controller
7:24
class, we should see that that error
right there has been resolved,
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since we created that method.
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At this point, we should at least be
able to see the category list page,
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even if it hasn't been
infused with live data.
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Let's redeploy and check it out.
7:44
So if your boot run task is still running,
go ahead and stop it.
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And after a few moments,
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you can rerun that bootRun task to reboot
your server and redeploy your web app.
7:52
And it looks like I have a compiler error.
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I see what happened here.
8:06
So this error right here says that I can't
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leave this generic between these
angle brackets here empty.
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And why does it say that?
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Well, it says that because in my
build file, if I go to my build file,
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build.gradle, I said I wanted
my Java source code to
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be compatible with Java five,
that is version 1.5, and
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I have to use source 7 or
higher to enable the diamond operator.
8:33
That's the operator that allows
us to leave that generic empty.
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So, what I'm going to do is, well, I could
do one of two things, I could remove
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the source compatibility here, I could
increase the source compatibility here, or
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I could go back to this line right here,
and actually add gif right there.
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I'm simply actually going to
delete the source compatibility.
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Delete that.
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We'll save it and
now I'm going to rerun the bootRun task.
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And there it looks like
the compilation has succeeded.
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And the web server's up and running.
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My application is deployed.
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Let's check it out.
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So I'm going to go back to my main page.
9:19
There's the home page,
we didn't touch it in this last task.
9:22
What we did touch, though,
is the Categories page.
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And there it is!
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It's working!
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We see that the template is actually
displayed, though it has static HTML.
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And from this, you can probably guess
what your final task is going to be.
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