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 already of my previous project. I didn't find any proper example project which uses this thing. Anyone please suggest me any working example where I can use GET and POST method in HTTP request
Using only the standard library with minimal code!
thread {
val jsonStr = try { URL(url).readText() } catch (ex: Exception) { return@thread }
runOnUiThread { displayOrWhatever(jsonStr) }
}
This starts a GET request on a new thread, leaving the UI thread to respond to user input. However, we can only modify UI elements from the main/UI thread, so we actually need a runOnUiThread
block to show the result to our user. This enqueues our display code to be run on the UI thread soon.
The try/catch is there so your app won't crash if you make a request with your phone's internet off. Add your own error handling (e.g. showing a Toast) as you please.
.readText()
is not part of the java.net.URL
class but a Kotlin extension method, Kotlin "glues" this method onto URL
. This is enough for plain GET requests, but for more control and POST requests you need something like the Fuel
library.
GET and POST using OkHttp
private const val CONNECT_TIMEOUT = 15L
private const val READ_TIMEOUT = 15L
private const val WRITE_TIMEOUT = 15L
private fun performPostOperation(urlString: String, jsonString: String, token: String): String? {
return try {
val client = OkHttpClient.Builder()
.connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)
.writeTimeout(WRITE_TIMEOUT, TimeUnit.SECONDS)
.readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
.build()
val body = jsonString.toRequestBody("application/json; charset=utf-8".toMediaTypeOrNull())
val request = Request.Builder()
.url(URL(urlString))
.header("Authorization", token)
.post(body)
.build()
val response = client.newCall(request).execute()
response.body?.string()
}
catch (e: IOException) {
e.printStackTrace()
null
}
}
private fun performGetOperation(urlString: String, token: String): String? {
return try {
val client = OkHttpClient.Builder()
.connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)
.writeTimeout(WRITE_TIMEOUT, TimeUnit.SECONDS)
.readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
.build()
val request = Request.Builder()
.url(URL(urlString))
.header("Authorization", token)
.get()
.build()
val response = client.newCall(request).execute()
response.body?.string()
}
catch (e: IOException) {
e.printStackTrace()
null
}
}
Object serialization and deserialization
@Throws(JsonProcessingException::class)
fun objectToJson(obj: Any): String {
return ObjectMapper().writeValueAsString(obj)
}
@Throws(IOException::class)
fun jsonToAgentObject(json: String?): MyObject? {
return if (json == null) { null } else {
ObjectMapper().readValue<MyObject>(json, MyObject::class.java)
}
}
Dependencies
Put the following lines in your gradle (app) file. Jackson is optional. You can use it for object serialization and deserialization.
implementation 'com.squareup.okhttp3:okhttp:4.3.1'
implementation 'com.fasterxml.jackson.core:jackson-core:2.9.8'
implementation 'com.fasterxml.jackson.core:jackson-annotations:2.9.8'
implementation 'com.fasterxml.jackson.core:jackson-databind:2.9.8'
Send HTTP POST/GET request with parameters using HttpURLConnection
:
POST with Parameters:
fun sendPostRequest(userName:String, password:String) {
var reqParam = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode(userName, "UTF-8")
reqParam += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode(password, "UTF-8")
val mURL = URL("<Your API Link>")
with(mURL.openConnection() as HttpURLConnection) {
// optional default is GET
requestMethod = "POST"
val wr = OutputStreamWriter(getOutputStream());
wr.write(reqParam);
wr.flush();
println("URL : $url")
println("Response Code : $responseCode")
BufferedReader(InputStreamReader(inputStream)).use {
val response = StringBuffer()
var inputLine = it.readLine()
while (inputLine != null) {
response.append(inputLine)
inputLine = it.readLine()
}
println("Response : $response")
}
}
}
GET with Parameters:
fun sendGetRequest(userName:String, password:String) {
var reqParam = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode(userName, "UTF-8")
reqParam += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode(password, "UTF-8")
val mURL = URL("<Yout API Link>?"+reqParam)
with(mURL.openConnection() as HttpURLConnection) {
// optional default is GET
requestMethod = "GET"
println("URL : $url")
println("Response Code : $responseCode")
BufferedReader(InputStreamReader(inputStream)).use {
val response = StringBuffer()
var inputLine = it.readLine()
while (inputLine != null) {
response.append(inputLine)
inputLine = it.readLine()
}
it.close()
println("Response : $response")
}
}
}
Have a look at Fuel library, a sample GET request
"https://httpbin.org/get"
.httpGet()
.responseString { request, response, result ->
when (result) {
is Result.Failure -> {
val ex = result.getException()
}
is Result.Success -> {
val data = result.get()
}
}
}
// You can also use Fuel.get("https://httpbin.org/get").responseString { ... }
// You can also use FuelManager.instance.get("...").responseString { ... }
A sample POST request
Fuel.post("https://httpbin.org/post")
.jsonBody("{ \"foo\" : \"bar\" }")
.also { println(it) }
.response { result -> }
Their documentation can be found here ?
I think using okhttp is the easiest solution. Here you can see an example for POST method, sending a json, and with auth.
val url = "https://example.com/endpoint"
val client = OkHttpClient()
val JSON = MediaType.get("application/json; charset=utf-8")
val body = RequestBody.create(JSON, "{\"data\":\"$data\"}")
val request = Request.Builder()
.addHeader("Authorization", "Bearer $token")
.url(url)
.post(body)
.build()
val response = client . newCall (request).execute()
println(response.request())
println(response.body()!!.string())
Remember to add this dependency to your project https://mvnrepository.com/artifact/com.squareup.okhttp3/okhttp
UPDATE: July 7th, 2019 I'm gonna give two examples using latest Kotlin (1.3.41), OkHttp (4.0.0) and Jackson (2.9.9).
UPDATE: January 25th, 2021 Everything is okay with the most updated versions.
<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.module/jackson-module-kotlin -->
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-kotlin</artifactId>
<version>2.12.1</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.squareup.okhttp3/okhttp -->
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>4.9.0</version>
</dependency>
Get Method
fun get() {
val client = OkHttpClient()
val url = URL("https://reqres.in/api/users?page=2")
val request = Request.Builder()
.url(url)
.get()
.build()
val response = client.newCall(request).execute()
val responseBody = response.body!!.string()
//Response
println("Response Body: " + responseBody)
//we could use jackson if we got a JSON
val mapperAll = ObjectMapper()
val objData = mapperAll.readTree(responseBody)
objData.get("data").forEachIndexed { index, jsonNode ->
println("$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() + ".")
}
For everybody stuck with NetworkOnMainThreadException for the other solutions: use AsyncTask or, even shorter, (yet still experimental) Coroutines:
launch {
val jsonStr = URL("url").readText()
}
If you need to test with plain http don't forget to add to your manifest:
android:usesCleartextTraffic="true"
For the experimental Coroutines you have to add to build.gradle as of 10/10/2018:
kotlin {
experimental {
coroutines 'enable'
}
}
dependencies {
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:0.24.0"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:0.24.0"
...
Without adding additional dependencies, this works. You don't need Volley for this. This works using the current version of Kotlin as of Dec 2018: Kotlin 1.3.10
If using Android Studio, you'll need to add this declaration in your AndroidManifest.xml:
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
You should manually declare imports here. The auto-import tool caused me many conflicts.:
import android.os.AsyncTask
import java.io.BufferedReader
import java.io.InputStreamReader
import java.io.OutputStream
import java.io.OutputStreamWriter
import java.net.URL
import java.net.URLEncoder
import javax.net.ssl.HttpsURLConnection
You can't perform network requests on a background thread. You must subclass AsyncTask
.
To call the method:
NetworkTask().execute(requestURL, queryString)
Declaration:
private class NetworkTask : AsyncTask<String, Int, Long>() {
override fun doInBackground(vararg parts: String): Long? {
val requestURL = parts.first()
val queryString = parts.last()
// Set up request
val connection: HttpsURLConnection = URL(requestURL).openConnection() as HttpsURLConnection
// Default is GET so you must override this for post
connection.requestMethod = "POST"
// To send a post body, output must be true
connection.doOutput = true
// Create the stream
val outputStream: OutputStream = connection.outputStream
// Create a writer container to pass the output over the stream
val outputWriter = OutputStreamWriter(outputStream)
// Add the string to the writer container
outputWriter.write(queryString)
// Send the data
outputWriter.flush()
// Create an input stream to read the response
val inputStream = BufferedReader(InputStreamReader(connection.inputStream)).use {
// Container for input stream data
val response = StringBuffer()
var inputLine = it.readLine()
// Add each line to the response container
while (inputLine != null) {
response.append(inputLine)
inputLine = it.readLine()
}
it.close()
// TODO: Add main thread callback to parse response
println(">>>> Response: $response")
}
connection.disconnect()
return 0
}
protected fun onProgressUpdate(vararg progress: Int) {
}
override fun onPostExecute(result: Long?) {
}
}
If you are using Kotlin
, you might as well keep your code as succinct as possible. The run
method turns the receiver into this
and returns the value of the block.
this as HttpURLConnection
creates a smart cast. bufferedReader().readText()
avoids a bunch of boilerplate code.
return URL(url).run {
openConnection().run {
this as HttpURLConnection
inputStream.bufferedReader().readText()
}
}
You can also wrap this into an extension function.
fun URL.getText(): String {
return openConnection().run {
this as HttpURLConnection
inputStream.bufferedReader().readText()
}
}
And call it like this
return URL(url).getText()
Finally, if you are super lazy, you can extend the String
class instead.
fun String.getUrlText(): String {
return URL(this).run {
openConnection().run {
this as HttpURLConnection
inputStream.bufferedReader().readText()
}
}
}
And call it like this
return "http://somewhere.com".getUrlText()
You can use kohttp library. It is a Kotlin DSL HTTP client. It supports the features of square.okhttp and provides a clear DSL for them. KoHttp async calls are powered by coroutines.
httpGet
extension function
val response: Response = "https://google.com/search?q=iphone".httpGet()
you can also use async call with coroutines
val response: Deferred<Response> = "https://google.com/search?q=iphone".asyncHttpGet()
or DSL function for more complex requests
val response: Response = httpGet {
host = "google.com"
path = "/search"
param {
"q" to "iphone"
"safe" to "off"
}
}
You can find more details in docs
To get it with gradle use
implementation 'io.github.rybalkinsd:kohttp:0.12.0'
import java.io.IOException
import java.net.URL
fun main(vararg args: String) {
val response = try {
URL("http://seznam.cz")
.openStream()
.bufferedReader()
.use { it.readText() }
} catch (e: IOException) {
"Error with ${e.message}."
}
println(response)
}
Source: Stackoverflow.com