HTTP Request in Kotlin

Question

I\'m completely new to Kotlin. I want to do a login validation using POST method and to get some information using GET method. I\'ve URL, server Username and Password alread

Answer 1

I think using okhttp is the easiest solution. Here you can see an example for POST method, sending a json, and with auth.

val url = "https://example.com/endpoint"

val client = OkHttpClient()

val JSON = MediaType.get("application/json; charset=utf-8")
val body = RequestBody.create(JSON, "{\"data\":\"$data\"}")
val request = Request.Builder()
        .addHeader("Authorization", "Bearer $token")
        .url(url)
        .post(body)
        .build()

val  response = client . newCall (request).execute()

println(response.request())
println(response.body()!!.string())

Remember to add this dependency to your project https://mvnrepository.com/artifact/com.squareup.okhttp3/okhttp

UPDATE: July 7th, 2019 I'm gonna give two examples using latest Kotlin (1.3.41), OkHttp (4.0.0) and Jackson (2.9.9).

Get Method

fun get() {
    val client = OkHttpClient()
    val url = URL("https://reqres.in/api/users?page=2")

    val request = Request.Builder()
            .url(url)
            .get()
            .build()

    val response = client.newCall(request).execute()

    val responseBody = response.body!!.string()

    //Response
    println("Response Body: " + responseBody)

    //we could use jackson if we got a JSON
    val mapperAll = ObjectMapper()
    val objData = mapperAll.readTree(responseBody)

    objData.get("data").forEachIndexed { index, jsonNode ->
        println("$index $jsonNode")
    }
}

POST Method

fun post() {
    val client = OkHttpClient()
    val url = URL("https://reqres.in/api/users")

    //just a string
    var jsonString = "{\"name\": \"Rolando\", \"job\": \"Fakeador\"}"

    //or using jackson
    val mapperAll = ObjectMapper()
    val jacksonObj = mapperAll.createObjectNode()
    jacksonObj.put("name", "Rolando")
    jacksonObj.put("job", "Fakeador")
    val jacksonString = jacksonObj.toString()

    val mediaType = "application/json; charset=utf-8".toMediaType()
    val body = jacksonString.toRequestBody(mediaType)

    val request = Request.Builder()
            .url(url)
            .post(body)
            .build()

    val response = client.newCall(request).execute()

    val responseBody = response.body!!.string()

    //Response
    println("Response Body: " + responseBody)

    //we could use jackson if we got a JSON
    val objData = mapperAll.readTree(responseBody)

    println("My name is " + objData.get("name").textValue() + ", and I'm a " + objData.get("job").textValue() + ".")
}