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Compose allows you to prepend your function to the start of the function chain.
Addendum
Whoops! I forgot to use the Markdown input I made. HTML can be passed through CommonMark without a problem. So here is the updated code, also available in the repository.
String result = Renderer.render(htmlInput, markeddownSanitizer);
System.out.println("HTML is safe...");
System.out.println(result);
result = Renderer.render(markdownInput, markeddownSanitizer);
System.out.println("Markdown is too...");
System.out.println(result);
Learn more
- Atlassian's commonmark
- Markdown Syntax
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Okay, so
0:00
now our application wants to allow users
to submit Markdown instead of HTML.
0:01
And we already have Markdown in our
library because we are using an open
0:06
source library called CommonMark.
0:10
And it's made by the people
over at Atlassian.
0:12
And I just wanted to give a quick shout
out here and thank companies who do that,
0:15
who allow us to use things.
0:20
They've built these things, it's very
common, you just wanna render a document,
0:21
you pass it some text and
it turns into HTML.
0:25
And let's take a look at what
some of that Markdown looks like.
0:27
But big shout out to those of you
out there that are making and
0:30
sharing open source work.
0:34
It really makes a difference.
0:36
So let's make a Markdown input here.
0:37
And I wanna make it
the same as what's here.
0:41
So, it's something like this.
0:43
Using strong tags, and
then to make a strong tag,
0:46
you do ** allows you to over promote.
0:51
All right,
we don't want that on our composure pages.
0:55
And links look like this.
0:58
So, Links open in a new browser.
1:00
So that's the text inside of it.
1:05
I'm running out of space over here.
1:09
Making use of this nice feature,
just press Enter, look at that.
1:12
Told you, it thinks of everything,
speaking of open source.
1:16
Okay, and
we're gonna say http://www.google.com.
1:19
Great, so
now we have some Markdown input, and
1:25
that method over there that we saw
is Markdown and it's called render.
1:29
And it takes a string,
and it returns a string.
1:34
And that string is HTML.
1:38
So right now we have our sanitizer,
we're moving forward but
1:39
I'm just gonna run this Markdown input
through so you can see what happens.
1:42
Our strong tag is back and
our link doesn't have external on there.
1:48
No, we've got to sanitize our stuff again.
1:55
But we already have the sanitizer, right?
1:57
We already have this right here.
1:59
So my guess is that we're just gonna
compose these together, right?
2:01
But we have a problem, before we did
this and then we put it at the end but
2:04
now we need to put it at the beginning.
2:08
So this is a good time to introduce
the compose method on a function.
2:12
So if I do sanitizer and
then I do .compose.
2:16
This basically just works the other way.
2:21
So what happens is it's
gonna run this first and
2:23
pass that into this function which is
then I got to pass this into this.
2:25
So it's like putting it at
the front of the chain.
2:29
Let's take a look and see what happens.
2:32
And boom.
2:36
We've got rid of our strong tag and
our rel external is visible.
2:36
And this is because it
ran this method first.
2:41
It took the Markdown,
passed it into the sanitizer which again,
2:43
the sanitizer is this
function all the way through.
2:46
So, as you can imagine,
I can also take this here and
2:49
I can extract a variable again and
2:54
I can call this markeddownSanitizer.
2:58
And of course I could export that and
3:02
share that wherever I
want in the code base.
3:04
Pretty slick, right?
3:07
So this is a great example of
breaking down composable function, so
3:09
that you can create a functional pipeline.
3:13
It's a great way to keep your composure
as these feature requests are coming in.
3:15
And that brings us to
the end of this workshop.
3:20
Please, let me know
what you thought of it.
3:22
I'd love to hear your feedback and
if you've got more ideas for
3:24
things that we can break down like this,
let me know.
3:27
See you soon.
3:29
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