HttpClient

Learn HttpClient configuration.

HttpClient configuration

When you create an HttpClient you can open a config block and add plugins. The most common plugin is ContentNegotiation, which handles JSON serialization automatically.

Example: HttpClient { install(ContentNegotiation) { json() } }. This block turns a JSON body into a Kotlin object automatically. Plugins are added with the install function. To switch engine you call HttpClient(CIO) { ... }. Central configuration means all requests share the same behavior.

JSON with ContentNegotiation

ContentNegotiation is the plugin that turns HTTP bodies into Kotlin objects automatically. With json() it uses kotlinx.serialization.

Once this plugin is added, client.get<User>(url) returns a User object directly. The body no longer needs manual parsing. The same applies to client.post bodies, which are serialized automatically. The plugin picks the format by looking at the Content-Type header: application/json for JSON, application/xml for XML.

Exercise Configure HttpClient and print

Configure the client with HttpClient { install(ContentNegotiation) { json() } }. Print println("Configured"), then close with client.close().

Show example solution

fun main() {
    val client = HttpClient {
        install(ContentNegotiation) { json() }
    }
    println("Configured")
    client.close()
}

Test yourself

Complete the install call

HttpClient {
    ____(ContentNegotiation) { json() }
}

Show answer

HttpClient {
    install(ContentNegotiation) { json() }
}

Match HttpClient plugins

ContentNegotiation

Converts JSON
install

Adds plugin
json()

Picks format
HttpClient

Client
Which function adds a plugin to HttpClient?
- use
- install
- with
- add
Show answer

install — answer: install. Plugins are added with install.

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