My earlier article launched Ktor and a few of its primary options for constructing net functions. Now, we’ll increase the instance utility developed in that article by including persistent knowledge and HTMX, which is able to present extra interactive views. This provides us a setup with loads of energy in a comparatively easy stack.
Please see the earlier article for the instance utility code and setup. We’ll construct on that instance right here.
Add persistence to the Ktor-HTMX utility
Step one towards making our utility extra highly effective is so as to add persistent knowledge. The preferred solution to work together with an SQL database in Kotlin is with the Uncovered ORM framework. It provides us a few methods to work together with the database, utilizing both a DAO mapping or a DSL. Kotlin’s native syntax means the general really feel of utilizing the ORM mapping layer has much less overhead than others you may need encountered.
We’ll want so as to add a number of dependencies to our construct.gradle.kt, along with these we have already got:
dependencies {
// present deps...
implementation("org.jetbrains.uncovered:exposed-core:0.41.1")
implementation("org.jetbrains.uncovered:exposed-jdbc:0.41.1")
implementation("com.h2database:h2:2.2.224")
}
You’ll discover we’ve included the uncovered core and JDBC libraries, in addition to a driver for the in-memory H2 database. We’ll use H2 as a easy persistence mechanism that may simply be converted to an exterior SQL database like Postgres in a while.
Add companies
To begin with, we’ll create a few easy companies that work together with a important service, which talks to the database. Right here’s our QuoteSchema.kt file to date, which units up the database schema and supplies service features for interacting with it:
// src/important/kotlin/com/instance/plugins/QuoteSchema.kt
package deal com.instance.plugins
import kotlinx.coroutines.*
import org.jetbrains.uncovered.sql.*
import org.jetbrains.uncovered.sql.transactions.transaction
object Quotes : Desk() {
val id: Column = integer("id").autoIncrement()
val quote = textual content("quote")
val creator = textual content("creator")
override val primaryKey = PrimaryKey(id, title = "PK_Quotes_ID")
}
knowledge class Quote(val id: Int? = null, val quote: String, val creator: String)
class QuoteService {
droop enjoyable create(quote: Quote): Int = withContext(Dispatchers.IO) {
transaction {
Quotes.insert {
it[this.quote] = quote.quote
it[this.author] = quote.creator
} get Quotes.id
} ?: throw Exception("Unable to create quote")
}
droop enjoyable checklist(): Record = withContext(Dispatchers.IO) {
transaction {
Quotes.selectAll().map {
Quote(
id = it[Quotes.id],
quote = it[Quotes.quote],
creator = it[Quotes.author]
)
}
}
}
}
There’s so much happening on this file, so let’s take it step-by-step. The very first thing we do is declare a Quotes object that extends Desk. Desk is part of the Uncovered framework and lets us outline a desk within the database. It does loads of work for us primarily based on the 4 variables we outline: id, quote, creator, and main key. The id ingredient might be auto-generated for an auto-increment main key, whereas the opposite two may have their acceptable column sorts (textual content turns into string, for instance, relying on the database’s dialect and driver).
Uncovered can also be sensible sufficient to solely generate the desk if it doesn’t exist already.
Subsequent, we declare an information class known as Quote, utilizing the constructor type. Discover id is marked as optionally available (since it is going to be auto-generated).
Then, we create a QuoteService class with two suspendable features: create and checklist. These are each interacting with the concurrent help in Kotlin, utilizing the IO dispatcher. These strategies are optimized for IO-bound concurrency, which is acceptable for database entry.
Inside every service methodology, we’ve got a database transaction, which does the work of both inserting a brand new Quote or returning a Record of Quotes.
Routes
Now let’s make a Database.kt file that pulls within the QuoteService and exposes endpoints for interacting with it. We’ll want a POST for creating quotes and a GET for itemizing them.
//src/important/kotlin/com/instance/plugins/Database.kt
package deal com.instance.plugins
import io.ktor.http.*
import io.ktor.server.utility.*
import io.ktor.server.request.*
import io.ktor.server.response.*
import io.ktor.server.routing.*
import java.sql.*
import kotlinx.coroutines.*
import org.jetbrains.uncovered.sql.*
import org.jetbrains.uncovered.sql.transactions.transaction
enjoyable Software.configureDatabases() {
val database = Database.join(
url = "jdbc:h2:mem:check;DB_CLOSE_DELAY=-1",
person = "root",
driver = "org.h2.Driver",
password = "",
)
transaction {
SchemaUtils.create(Quotes)
}
val quoteService = QuoteService()
routing {
put up("/quotes") {
val parameters = name.receiveParameters()
val quote = parameters["quote"] ?: ""
val creator = parameters["author"] ?: ""
val newQuote = Quote(quote = quote, creator = creator)
val id = quoteService.create(newQuote)
name.reply(HttpStatusCode.Created, id)
}
get("/quotes") {
val quotes = quoteService.checklist()
name.reply(HttpStatusCode.OK, quotes)
}
}
}
We start through the use of Database.join from the Uncovered framework to create a database connection utilizing customary H2 parameters. Then, inside a transaction we create the Quotes schema, utilizing our Quotes class we outlined in QuoteSchema.kt.
Subsequent, we create two routes utilizing the syntax we developed in the primary stage of this instance and counting on the create and checklist features and Quote class from QuoteSchema.
Don’t overlook to incorporate the brand new operate in Software.kt:
// src/important/kotlin/com/instance/Software.kt
package deal com.instance
import com.instance.plugins.*
import io.ktor.server.utility.*
import io.ktor.server.response.*
import io.ktor.server.routing.*
enjoyable important(args: Array) {
io.ktor.server.netty.EngineMain.important(args)
}
enjoyable Software.module() {
configureTemplating()
//configureRouting()
set up(RequestLoggingPlugin)
configureDatabases()
}
Discover I’ve commented out the outdated configureRouting() name, so it received’t battle with our new routes.
To do a fast check of those routes, we are able to use the curl command-line device. This line inserts a row:
$ curl -X POST -H "Content material-Kind: utility/x-www-form-urlencoded" -H "Host: localhost:8080" -d "quote=FooBar.&creator=William+Shakespeare" http://localhost:8080/quotes
And this one outputs the prevailing rows:
$ curl http://localhost:8080/quotes
Utilizing HTMX for interactive views
Now let’s bounce proper into making a UI to work together with the companies utilizing HTMX. We wish a web page that lists the prevailing quotes and a type that we are able to use to submit a brand new quote. The quote might be dynamically inserted into the checklist on the web page, with out a web page reload.
To attain these objectives, we’ll want a route that pulls every thing on the outset after which one other route that accepts the shape POST and returns the markup for the newly inserted quote. We’ll add these to the Database.kt routes for simplicity.
Right here is the /quotes-htmx web page that offers us the preliminary checklist and type:
get("/quotes-htmx") {
val quotes = quoteService.checklist()
name.respondHtml {
head {
script(src = "https://unpkg.com/htmx.org@1.9.6") {}
}
physique {
h1 { +"Quotes (HTMX)" }
div {
id = "quotes-list"
quotes.forEach { quote ->
div {
p { +quote.quote }
p { +"― ${quote.creator}" }
}
}
}
type(methodology = FormMethod.put up, motion = "/quotes", encType = FormEncType.applicationXWwwFormUrlEncoded) {
attributes["hx-post"] = "/quotes"
attributes["hx-target"] = "#quotes-list"
attributes["hx-swap"] = "beforeend"
div {
label { +"Quote:" }
textInput(title = "quote")
}
div {
label { +"Creator:" }
textInput(title = "creator")
}
button(sort = ButtonType.submit) { +"Add Quote" }
}
}
}
}
First, we seize the checklist of quotes from the service. Then we begin outputting the HTML, starting with a head ingredient that features the HTMX library from a CDN. Subsequent, we open a physique tag and render a title (H1) ingredient adopted by a div with the id of quotes-list. Discover that id is dealt with as a name from contained in the div block, as a substitute of as an attribute on div.
Inside quotes-list, we iterate over the quotes assortment and output a div with every quote and creator. (Within the Specific model of this utility, we used a UL and checklist gadgets. We may have completed the identical right here.)
After the checklist comes the shape, which units a number of non-standard attributes (hx-post, hx-target, and hx-swap) on the attributes assortment. These might be set on the output HTML type ingredient.
Now all we’d like is a /quotes route to just accept the incoming quotes from POST and reply with an HTML fragment that represents the brand new quote to be inserted into the checklist:
put up("/quotes") {
val parameters = name.receiveParameters()
val quote = parameters["quote"] ?: ""
val creator = parameters["author"] ?: ""
val newQuote = Quote(quote = quote, creator = creator)
val id = quoteService.create(newQuote)
val createdQuote = quoteService.learn(id)
name.respondHtml(HttpStatusCode.Created) {
physique{
div {
p { +createdQuote.quote }
p { +"― ${createdQuote.creator}" }
}
}
}
That is fairly easy. One wrinkle is that Kotlin’s HTML DSL doesn’t wish to ship an HTML fragment, so we’ve got to wrap our quote markup in a physique tag, which shouldn’t be there. (There’s a easy workaround we’re skipping for simplicity, present in this venture known as respondHtmlFragment). It appears seemingly that producing HTML fragments will ultimately grow to be a normal a part of the HTML DSL.
Apart from that, we simply parse the shape and use the service to create a Quote after which use the brand new Quote to generate the response, which HTMX will use to replace the UI dynamically.
Conclusion
We went quick and lean with this instance, to discover the essence of Ktor. Nonetheless, we’ve got all the weather of a extremely performant and dynamic stack with out a lot overhead. As a result of Kotlin is constructed on prime of the JVM it provides you entry to every thing Java does. That, coupled with its highly effective union of object-oriented and purposeful programming, and DSL capabilities, makes Kotlin a compelling server-side language. You should utilize it for constructing functions with conventional RESTful JSON endpoints, or with dynamic HTMX-powered UIs, as we’ve seen right here.
See my GitHub repository for the entire supply code for the Ktor-HTMX utility instance.