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When you were earning about http,

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you probably heard about
something called cookies.

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Now cookies are bits of data that
are stored on the client and

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are sent on each request
to a specific domain.

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Now, one of the hardest things about using
cookies is avoiding the impulse to say,

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me want cookie, a la Cookie Monster.

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So now that I've got that out of the way,
hopefully I won't do that again.

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I'm sorry about that.

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You can set a cookie on a response and
read it on all future requests.

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That sounds exactly like what we wanna do.

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Let's go use some cookie power.

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Okay, so first thing's first,

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let's go extract that query
parameter that we pulled here.

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Let's put that into its own variable.

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So again,
what you do is you highlight that, and

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you choose Refactor, Extract, Variable.

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And what that will do is it will pull
out a brand new variable line, and

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it's gonna try to name it.

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Did a great job.

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Username's fine.

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And it replaces it.

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So now, this variable is able,
we're able to use this variable twice.

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It's the point of a variable,
the local variable.

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So on the response object,
the ability to set a cookie exists.

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So you do a cookie, and then you save the
name of the cookie that you want it to be.

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So we want it to be called username.

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And we want to set it to that
new variable that we just did.

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Okay, so now every request
that gets sent to our domain,

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which in our case here is localhost.

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It will receive this data.

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Do you wanna see it?

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Cool, let's do it.

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So let's go come here.

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And we will reboot the server.

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And we'll fly over to our page.

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I have my network tools up.

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I'm gonna go ahead, and
I'm gonna type craigsdennis.

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But before I click Sign in,
I wanna show you something.

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So, this is shortend cuz
my screen is smaller here,

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but at these little arrows there's
a thing here called resources.

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Now look at resources.

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There is a thing called cookies and
then there's a thing that says localhost.

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This site has no cookies
because we haven't set it yet.

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Right?

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So I'm gonna set it and when I click send.

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It's gonna run through our sign-in.

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It's gonna pull the request off,
and it's gonna set the cookie.

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Boom, and there it is.

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It's set.

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Okay?.
So

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now you see that the user
name is craigsdennis.

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And now, if I come back,
and I hit the homepage,

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you'll see that the cookies
are still there.

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And if we look back over
here at our network tab.

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Let's look at that again.

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Hit All.

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Look at the local host page here.

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You can see that the cookie has,
it's there, and it's available.

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Let's make the homepage aware of whether
or not we've gathered their username.

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So we need to make a model.

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Right?

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So let's make that same
model like we did before.

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So we'll just do the same thing,
and we'll make a new map.

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And it's a new map of key
values that are both strings.

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And it's called model

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And we'll make a new HashMap.

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It's call String, String.

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Okay, and we are going to put into our
model, we're gonna put a new value

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called username, and
we're gonna pull that cookie.

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So the way that you do that
is just like you might think.

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You just say cookie, and
then the name of the cookie.

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And that will get that value that's there.

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Okay, and now our index.hbs
needs to know about the model.

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And now our template knows
about the username value.

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So let's use it, right?

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Let's go and let's look at our.

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Resources.

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And we'll look in here.

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We'll look under index.

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And what we wanna do is we wanna only
say hello if we know their name.

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So the way to do that in Handlebars is
to use what's known as a block helper.

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So a black helper, you do a pound.

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And the block helper here in this case is
something you're familiar with already.

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It's called if.

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So we're gonna say if username.

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It's a little bit different
of an if than you're used to.

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It's if that exists in the model,
that key exists in the model,

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then run this code that's
inside these two if blocks.

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So we're gonna say h1, Welcome, username.

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Okay?

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And then if we don't know what it is,
we wanna have a block called else.

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So, in here there is an else.

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Okay, and we can grab this code here,
and we can move it up.

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So now what's happening is it comes in.

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It says if there is a username
on the model, show this message,

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Welcome username.

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Otherwise show Welcome Students.

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I Better put the exclamation point here,
so they both get exclmationed.

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All right, so let's go ahead and
we'll click run.

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We'll do a run, and
we'll restart the server.

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All right.

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Let's look at our index page.

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Awesome.

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So that's using the first part of the if,
and it's using the cookie.

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So we can prove that by if we
come over here to the Cookies.

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If you click the Cookies in Chrome,
you can press Delete, and

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now the site has no cookies.

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And now if I refresh this page,
we'll see our form.

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And we can put in our name.

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That prompt is back.

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We don't really need this page anymore,
do we?

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We don't need this sign in page.

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We could just drop them here.

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Awesome.

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By adding cookies to our bag of tricks,

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we now have the core tool set used to make
a web application appear to be stateful.

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You'll find these patterns
of forum submission and

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storing values in cookies very relevant.

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Now that you know these terms,

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it's more a question of how
each framework implements them.

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Try to remember, this is all just sitting
on top of HTTP and providing a nice to use

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abstraction but really not doing
to much more at it's core.

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You should be able to start
understanding most web frameworks now.

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We should have all the tools we need
to start building out the rest of our

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application.

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Let's go do that, and along the way I'll
show you some handy Spark specific tricks

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right after these messages.