Ktor post json. respond() function to pass a data object in a response: I have a post request done with Ktor this way val response = httpClient. features. By the end of this tutorial you will know how to do the following: Now, we can retrieve the Post class object from the response body string received from the server: val responseBody = response. Special in this case is that we want to specify parameters and use them then in the reponse. 我已定义了数据类，配置了gson并创建了处理post请求的路由，如下所示：data class PurchaseOrder (val buyer: String, val seller: StrinHow to receive JSON object in Ktor? Learn how to build a REST API using Kotlin and Ktor with this hands-on tutorial. Object  To enable serialization of data objects in Ktor, you need to install the ContentNegotiation plugin and register a required converter (for example, JSON). Also the reverse proxy might be serving via HTTPS and requesting to your server via HTTP. It’s an ideal entry-level tutorial for Kotlin backend developers. Use the client to make HTTP requests to your test application and receive responses. testing. serialization framework if needed. Welcome back to our journey with the Ktor framework. content val bytes: ByteArray = response. Note that serializers for specific formats require additional artifacts. Jun 26, 2021 · I found the data is sent as a String in Ktor while all is a plain JSON with curl or Python. Verify responses using Simplifying Data Validation in Ktor with ValidationBuilder As a developer transitioning from Spring + Kotlin to Ktor, I encountered a challenge that many of you might relate to. Use the println() function to print a status code returned by the server and the close() function to close the stream and release any resources associated with it. For this I used a simple json api call via To validate a request body, use the validate function. The code works when I define four data clas In IntelliJ IDEA, click the red bulb next to the definition and choose Make main suspend. json. Learn to serialize and deserialize JSON in Ktor. Contribute to ktorio/ktor-samples development by creating an account on GitHub. Add Features using Ktor Modules Ktor uses modules to encapsulate specific features for example serialization and routing can be added to the application like so: Learn how to develop a cross-platform full-stack application in Kotlin and Ktor. kt file should look in the following way: Retrofit2 мне, как Android разработчику, нравится, но как на счет того, чтобы попробовать к качестве HTTP клиента Ktor? На мой взгляд, для Android разработки он не хуже и не лучше, просто один из To stream large or dynamic content efficiently, you can use MultiPartFormDataContent with an InputProvider. readText() val readChannel = response. This guide provides practical steps for efficient data handling in your Kotlin applications. Please note that some of response types are Closeable and can hold resources. This causes the SerializationException because the JsonFeature tries to serialize MultiPartFormDataContent object. REST APIs allow your Android app to … 如何使用 kotlin 和 ktor 在 POST 请求中添加 JSON 字符串？ 打印出从文件读取的 Json 字符串，甚至在客户端用 Kotlin 构建的字符串，内容看起来像 JSON。 尽管如此，服务器仍无法将字符串识别为 JSON，并且当我在服务器中打印它时，每个双倍配额都会被反斜杠。 客户端显然添加了反斜杠，因此请求没有按 Deserializing JSON from Requests Ktor excels at automatically deserializing incoming JSON payloads directly into your defined Kotlin data classes. The Main. Quickly serialize and deserialize JSON in Ktor. Ktor provides a ContentNegotiation plugin to negotiate the media type of request and deserialize content to an object of a required type. This capability significantly streamlines the process of handling POST and PUT requests, eliminating much of the boilerplate code typically associated with request body parsing. This library provides ktor client interface integration for the json-kotlin library. I am new to Ktor and I have a route with a request body which i am parsing with Kotlin Serialization. 2 onwards, this library uses the json-streaming library for on-the-fly JSON parsing. Nov 15, 2025 · This guide walks you through effectively parsing incoming JSON requests and generating JSON responses using Ktor's built-in capabilities. jackson. I've found nearly everywhere in ktor-client documentation and examples they use empty formData to show how the client works formParameters: Parameters = Parameters. Json) setBody (UnfollowRequestBody (userId, In this tutorial, you’ll learn the basics of routing, handling requests, and parameters in Kotlin with Ktor by building a task manager application. Uploading multipart form data using Ktor In this tutorial, we will learn how to make multipart form data post calls to upload files and Http form data. Ktor Client allows you to make requests and handle responses, extend its functionality with features, such as authentication, JSON serialization, and so on. After upgrading to V1. I know that the request body is expected to conform to the request body data class but then, I Hey buddy! I wanted to share something cool I’ve been working with lately — using Ktor to make API calls in Android apps. Sample projects for Ktor. I already know how to receive a JSON object and automatically deserialize it into the required format (e. Ktor supports the following formats out-of-the-box: JSON, XML, CBOR, and ProtoBuf. Sep 18, 2020 · In this article you will learn how to create a post route which receives json, does some logic with the content of the json and returns json content to the executor. client. fasterxml. This means that the input data is parsed into an internal form as it is being read, and avoids the need to allocate Beyond live game broadcasts, ESPN creates an entire entertainment ecosystem around football that includes pre-game analysis shows, post-game discussions, fantasy football integration, and year-round content that keeps fans engaged during the off-season. LinkedTreeMap cannot be cast to MyClass If i post simple object and parse it in ktor with call. To solve your problem you can access URL parameters by referring them with call. receive Ktor Documentation Ktor is a framework for building asynchronous server-side and client-side applications with ease. 3. Update: all looks ok with JsonElement from Json. See below the screenshots of the … Making HTTP Requests in Kotlin using Ktor As an app developer, you may need to interact with remote servers by sending and receiving data over HTTP. Perfect for beginners looking to get started with web development. serialization API Integration: Makes HTTP requests to external weather services I have data class defined, configured gson and created rout to handle post request as follows: data class PurchaseOrder(val buyer: String, val seller: String, val poNumber: String, val date: Stri Ktor: POST request with parameters In this tutorial we will create another POST-Route. A parsed JWT token. In this tutorial, you will discover how to use Kotlin Multiplatform to build for Android, iOS, and desktop, and handle data effortlessly using Ktor. post ("$ {BASE_URL}/following") { contentType (ContentType. Empty So what's the kotlin/ktor Thank you @AlekseiTirman, I figured out that it is in io. receive<MultiPartData>() val inputStream = response. g. In above code second line throws exception com. You Deserializing JSON from Requests Ktor excels at automatically deserializing incoming JSON payloads directly into your defined Kotlin data classes. In Kotlin, Ktor is a lightweight and powerful … JSON Web Token is an open standard for securely transmitting information between parties as a JSON object. serialization seamlessly, enabling robust data handling. HttpResponse exposes the API required to get a response body in various ways (raw bytes, JSON objects, etc. Thank you Aleksei, I have the JsonFeature enabled, so ktor created a json-string out of a json-string :D Thanks for pointing me to the right driectionproblem solved. But before we start actual coding, lets This article is about how to create a simple REST API using Ktor and Exposed. 今天我們就來談談怎麼用 Ktor 處理 JSON 格式的回傳。 jackson 我們可以看看專案裡面 jackson 的安裝範例 install(ContentNegotiation) { jackson { enable(SerializationFeature. So issue is only when parsing list of objects. parameters and manually create ShowPostURL object. serializer. Ktor is a framework for building asynchronous servers and clients in connected systems using the powerful Kotlin programming language. In Ktor, you can verify a token and validate the claims contained within it using the jwt authentication. * import io 使用 Python 的 requests 库发送 POST 请求（data vs json 参数详解） 在使用 requests. Depending upon the query, the response may contain a list of one of two types. Customizing requests 我们不能只进行 get 请求，Ktor 允许使用任何 HTTP 动词构件复杂请求，并且灵活地以多种方式处理响应。 Default http methods 与 request 类似，还有几个可以 使用最常见的 HTTP 动词（GET 、 POST 、 PUT 、 DELETE 、 PATCH 、 HEAD 以及 OPTIONS Learn how to use Ktor Client for HTTP requests in Android, explore its engine plugin, customization options, and see a real-world app demo. You have the line contentType(ContentType. With MultiPartFormDataContent, you can also monitor upload progress using the onUpload callback. In this tutorial you will learn how to create, open and run a new Ktor project. Oct 20, 2025 · Negotiating media types between the client and server. Here's the curl command for reference: curl -X POST -H 要能回传 json 格式的资料，我们需要安装新的套件 安装套件之前，我们先将 IntelliJ Idea 的 auto import 打开 我们打开 Preferences > Build, Execution, Deployment > Gradle 点开视窗之后，我们勾选里面的“Automatically import this project on changes in build script files” 然后点视窗右下方的“Apply” 这样，之后我们更新 build Fetching Data from an API Using Ktor in Your Android App Follow along as we build a simple Comments App that fetches data from the network using the Ktor library. ClientProvider. The JSON Lines format is particularly suitable for streaming data, and the kjson-ktor library includes functions to output JSON Lines data from a Channel or a Flow: Content Negotiation: converts request body based on the content type header. Ktor Client is an efficient way of executing HTTP request in Android projects which also supported in Kotlin Multiplatform. InputProvider allows you to supply file data as a buffered stream rather than loading it entirely into memory, making it well-suited for large files. Ktor is a powerful Kotlin-based framework for building asynchronous servers and clients, and i Previously, the API returned this response at the root path: call. You'll learn how to integrate libraries like Jackson or kotlinx. They look the same when you print them, but of course they are not equally interpreted by the JVM. ktor:ktor-client-json-js artifact. ) allow you to receive a response as an HttpResponse object. Optionally, configure the HTTP client. What I will cover? Create simple POST request with ktor In this tutorial we will create our first POST-Route in ktor and test it. 首先，必须创建 HTTP Request 文件（api 或者 http 扩展名 How to Make HTTP Requests With Ktor — Android Grab a cup of coffee ☕, and explore the type-safe HTTP client called Ktor. But not sure how should I send JSON properly. Serializable @Serializable data class ResponseData(val id: Int, val value: String) suspend fun fetchAndProcessData() { The ability to perform file uploads and downloads is a staple part of any good web server framework. string to get the response object as a string, you could then get single JSON keys and their corresponding values. For more information, see Receiving responses. This function returns a ValidationResult object representing a successful or unsuccessful validation result. Popular We are sending a post request using Ktor. Learn how to use Kotlin and Ktor to build a single-page application (SPA) in which RESTful services link to database repositories. ktor. You can test a Ktor application using the testApplication {} function and the provided HTTP client. They give a nice example of how to test a GET endpoint here, however I'm having trouble with an http POST. To use this feature with Kotlin/JS, you need to include the io. Is there a complete documentation? According to this, I need to use httpClient. Enjoy! :-)Thank you for commenting and asking questions. Learn how to integrate Kotlinx. Then serialize it with the kotlinx. bodyAsText() val post = Json. Json) that sends the Content-Type header with application/json value. serialization for efficient data handling in your web applications. Serializers The JsonFeature has a default serializer (implicitly obtained or by calling defaultSerializer()) based on a ServiceLoader on JVM (supporting Gson or Jackson depending on the artifact included), and a serializer based on kotlinx. It uses the Exposed SQL library and allows you to fake repositories for testing. Here's how to configure it: Handling HTTP responses efficiently requires understanding Ktor's tools for parsing and processing responses. server. Configure and run a test instance of your application. Get started with building your first Ktor Server application. 2 to support kotlin 1. receive() function that accepts a data class as a parameter: Learn to build Kotlin RESTful APIs with Ktor. Also look here: How to receive JSON object in Ktor? My problem now i All functions used to make an HTTP request (request, get, post, etc. For example, kotlinx. serialization. Jan 20, 2026 · HttpResponse exposes the API required to get a response body in various formats – such as a string, a JSON object, and more – as well as retrieving response parameters, such as a status code, content type, and headers. HttpResponse 类 这里 列出了 HttpResponse 的 API 参考。 通过 HttpResponse 可以轻松获取响应内容： val readChannel: ByteReadChannel = response. ktor:ktor-client-json dependency added. Manually parsing incoming data and building a JSON string for every response is not ideal. As part of my series “An opinionated Kotlin backend service”, I was checking out different ways to serialize/deserialize JSON payloads 3 For the Ktor http client to deserialize to your custom object, you would need to install JsonFeature while creating your http client, which would need the io. Serializing/deserializing the content in a specific format when sending requests and receiving responses. decodeFromString<Post>(responseBody) 如何使用kotlin和ktor在POST请求中添加JSON字符串？ 打印出从文件中读取的JSON字符串，甚至在客户端使用Kotlin构造字符串，内容看起来像Json。 尽管如此，服务器不能将字符串识别为JSON，并且当我在服务器中打印它时，每个双倍配额都被反斜杠。 In this tutorial, we will explore how to use Ktor Android Client to make all types of HTTP requests including GET, POST, PUT, DELETE, and form submissions. submitFormWithBinaryData but can’t find how to change the default POST method. Post request a raw json with Ktor client Asked 3 years, 6 months ago Modified 7 months ago Viewed 3k times How can I send POST request to other server with Ktor server? Asked 5 years, 3 months ago Modified 2 years, 10 months ago Viewed 10k times All functions used to make an HTTP request (request, get, post, etc. And the only way I could think of including the [] in the json was with listOf but I am not even sure it is writing it correctly hence the need to see exactly what Ktor is sending in Json. with a data class). but I don't know how to specify parameters, I read the I am working on an Android app that uses Ktor for HTTP requests to an API. Conclusion In this post, we extended the HTTP API created in the previous post to secure the protected and admin endpoints with native JWT validation support provided by Ktor. ) and obtain response parameters, such as a status code, content type, and headers. google. For an unsuccessful result, RequestValidationException is raised. import io. Edit page Last modified: 20 October 2025 After adding the client dependencies, you can instantiate the client by creating the HttpClient class instance and passing an engine as a parameter: With retrofit, you can use response. Today, we take things a step further with a hands-on approach, showing you how to Reverse proxy support: origin and local When behind a reverse-proxy (for example an nginx or a load balancer), the received request is not performed by the end-user, but that reverse proxy. That means that the client IP address of the connection would be the one of the proxy instead of the client. It facilitates developing a standalone application with embedded servers. Ktor has support for both operations in just a few lines. Thankfully, there’s a Example of Posting Data with Forms 编辑本页 预计阅读时间： 1 分钟 Browse the source code on GitHub: ktor-samples-post JWT authorization flow  The JWT authorization flow in Ktor might look as follows: A client makes a POST request with the credentials to a specific authentication route in a server application. The validate function has two overloads allowing you to validate a request body in two ways: The first validate overload allows you to access a request body as the I'm trying to send a POST request to the server, this post requires parameters "email" and "password". receive<MyClass>() then it will work fine. The example below shows an HTTP client POST request with the credentials passed in JSON: 现在是时候试一下后端服务了。 如果有 IntelliJ IDEA Ultimate，可以使用其 HTTP 请求客户端； 如果没有，也可以使用 postman 或者 curl： IntelliJ IDEA Ultimate： IntelliJ IDEA Ultimate 还有 PhpStorm 以及其他 JetBrains IDE 都包含一个 很好的 基于编辑器的 Rest 客户端. Recently I had a problem, where I should get the last successful build hash of a Jenkins Job. Jan 13, 2021 · The solution is to pass to the HTTP POST request a JSON object not a String object. You use json configuration function which is most likely is not appropriate for the configuration of ContentNegotiation. We then created an Auth0 API and application and accessed our backend API by a sample frontend application integrated with Auth0. Our previous post introduced you to JSON Web Tokens (JWT) and their impact on authentication in modern web applications. You can use JSON Web Tokens for authorization: when the user is logged in, each request will include a token, allowing the user to access resources that are permitted with that token. kts file, add the necessary dependencies for Ktor and any other libraries you might need, like Ktor serialization for JSON handling. createClient but got Cannot importcreateClient, functions and properties can be imported only from packages or objects How do I send json in form data from the ktor client and receive it on a ktor server? I need multiple keys (json and json2) with json data in them in the same request. Get started with Ktor Server Learn how to create, run and test a server application with Ktor. I'm trying to get the username, email, password, password_check from a composable textField in kotlin, then within ktor to send an HTTP post request to my django REST API. To receive and convert content for a request, call the ApplicationCall. This tutorial covers setup, routing, and testing on a real-life example. But can’t find the proper way to do this. INDENT_OUTPUT) } } 這個部分幫我們安裝了一個 ContentNegotiation 的套件：jackson import com. HI, I am developing an app which generates Images from text using Stability AI the code uses KTor which is as follows suspend fun… The ContentNegotiation feature in Ktor provides a way to serialize and deserialize objects into JSON using libraries like Jackson or kotlinx. For this, it uses the Accept and Content-Type headers. receive<ByteReadChannel>() val multiPart = response. databind. post () 方法时，我们经常会遇到 data 和 json 两个参数，它们在传递数据时有着不同的用途和行为。 Hello, I’m trying to upload a JSON file with a PUT method. * import kotlinx. gson. tv/$/invite/@mikemoellernielsen:9Get 25 % discount on your Add Dependencies: In your build. You learned about the key benefits of JWT, such as statelessness, improved scalability, cross-platform compatibility, and enhanced security. Ktor (kotlin web framework) has an awesome testable mode where http requests can be wrapped in unit tests. kotlinx. Ktor is a framework for building asnchronous servers with the kotlin programming … Building Connected Applications with Ktor: A Deep Dive into JSON and Data Serialization (Part 2) Welcome back to our Ktor journey! Before if you not check with our initial setup then please visit Ktor — full type safe json api with endpoint definitions Ktor Endpoints One nice thing of using Ktor is that you can share some code between the server app, and the client -with KMP it can be a … To stream large or dynamic content efficiently, you can use MultiPartFormDataContent with an InputProvider. respondText("{\\"message\\":\\"Hello World!\\"}") As we add new features, the API’s codebase will grow, and we will need to represent requests and responses using data classes to make the code more maintainable. readBytes() val text: String = response. From version 0. Then, you can use the call. Dec 5, 2024 · This article aims to guide you through making GET and POST requests with Ktor client, which is a powerful and flexible HTTP client library that is suitable for both Android applications and web server applications. parseToJsonElement(data) Tool Handlers: Implements handler functions for weather-related tools Client-Side Components HttpClient Configuration: Creates a Ktor HttpClient with CIO engine Content Negotiation: Configures automatic JSON serialization using kotlinx. * import io. internal. Serialize JSON HttpResponse to Kotlin Objects with Ktor. If you’re… Ktor JSON Parsing on Post Request is not working Asked 3 years, 11 months ago Modified 3 years, 9 months ago Viewed 1k times I'm trying to create a multipart/form-data POST request in Ktor using Kotlin, similar to an HTTP request I previously implemented using curl. serialization: serialize/deserialize JSON (and other formats if needed). 7, the request body started showing empty and nothing is actually sent in the body. gradle. serialization for Native as well as for JavaScript. To achieve this is in Ktor, use response Getting Started with REST API in Android using Ktor Introduction In the world of Android development, working with REST APIs is a common and essential task. Library sign up referral link:https://lbry. serialization requires the ktor-serialization-kotlinx-json dependency for JSON. A typical workflow includes the following steps: Define a test using testApplication {}. Application. 0qkmx, ti1aa, kio3, 8b4g, naod, uqqn, 7naxnl, wvhzwk, c4vh, 25pu7,