The official Kotlin documentation includes an example of a DSL for working with HTML. The example includes a playground to work with the DSL to see how the different functions work.
The following code snippet demonstrates the usage of this Kotlin DSL to declare valid HTML code via Kotlin syntax:
fun main() {
val result = html {
head {
title { +"HTML encoding with Kotlin" }
}
body {
h1 { +"HTML encoding with Kotlin" }
p {
+"this format can be used as an"
+"alternative markup to HTML"
}
// an element with attributes and text content
a(href = "http://jetbrains.com/kotlin") { +"Kotlin" }
// mixed content
p {
+"This is some"
b { +"mixed" }
+"text. For more see the"
a(href = "http://jetbrains.com/kotlin") {
+"Kotlin"
}
+"project"
}
p {
+"Can even leverage loops and control flow"
ul {
for (i in 1..3)
li { +"${i}*2 = ${i*2}" }
}
}
}
}
println(result.toString())
}
The preceding code makes use of various functions as well as control flow structures. It's a good example of how you can develop a DSL to abstract away details of a problem space. In this case, you don't need to remember the exact syntax for each HTML element, and instead can rely on statically typed functions to build your document definition.
The previous code snippet will generate the follow result when printed to the screen:
<html>
<head>
<title>
HTML encoding with Kotlin
</title>
</head>
<body>
<h1>
HTML encoding with Kotlin
</h1>
<p>
this format can be used as an
alternative markup to HTML
</p>
<a href="http://jetbrains.com/kotlin">
Kotlin
</a>
<p>
This is some
<b>
mixed
</b>
text. For more see the
<a href="http://jetbrains.com/kotlin">
Kotlin
</a>
project
</p>
<p>
Can even leverage loops and control flow
<ul>
<li>
1*2 = 2
</li>
<li>
2*2 = 4
</li>
<li>
3*2 = 6
</li>
</ul>
</p>
</body>
</html>
This approach for building a DSL for HTML is similar to the approach being taken in the development of the Jetpack Compose library for Android development, which is a Kotlin-based DSL for building a declarative UI.