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UdemyKotlinPaid courseAll LevelsCertificate

Build RESTFUL APIs using Kotlin and Spring Boot (Udemy.com)

A complete hands on approach to learn the Kotlin language and build Restful APIs using Kotlin SpringBoot.

Created by: Pragmatic Code School

Last updated February 2026

Our take

Based on the ratings of 1,485 students, a sample of their written reviews and the syllabus, as the course stood in February 2026. No course pays to be reviewed.

Pragmatic Code School's course is aimed squarely at Java developers who already know Spring Boot. It spends roughly the first half on Kotlin basics: classes, null handling, collections, lambdas and scope functions. The second half builds a course catalog REST service with Spring Data JPA, validation, Postgres and TestContainers tests. It runs about 8.4 hours across 93 lectures, and over 10,000 students have enrolled. The requirements are real: Java, Spring Boot and Maven or Gradle experience are all expected.

Reviewers like the calm, concise teaching and how quickly the fundamentals go by. One called the first half short, fast-moving code walk-throughs, and a developer with one week to prepare for a senior role was glad to have picked it. About 87 percent of the ratings are four or five stars. The complaints are consistent. More than half the course is Kotlin rather than APIs, and one reviewer wants it split, with coroutines added. Others call it basic on internals, note the lack of JWT security and Swagger docs, and say the IntelliJ and Kotlin versions have moved on.

At 8.4 hours this is a quick way in, not a deep one. The last update was February 2026, yet recent reviewers still hit version trouble, so expect to adjust the setup. One reviewer also mentions a misleading assignment and a final section that shows code students never wrote. Recommended for Java developers who want Kotlin habits and a tested Spring example fast. Anyone new to Spring should start elsewhere.

Best forJava and Spring Boot developers who want to pick up Kotlin quickly and build one tested REST service.
Skip it ifYou want coroutines, JWT security, Swagger docs or a deep look at internals.

Pros

  • Kotlin fundamentals move fast, so Java developers reach the Spring Boot build in about half the course
  • Covers testing properly: JUnit5, Mockk, @DataJpaTest and TestContainers against Postgres
  • Calm, concise explanations that reviewers call simple and to the point
  • Source code and slides are provided, so students can code along or compare

Cons

  • More than half the runtime is Kotlin basics, so the REST API part is thinner than the title suggests
  • Reviewers report older IntelliJ and Kotlin versions, and some struggled to get the setup working
  • No JWT security, Swagger docs or coroutines, and some find the treatment basic on internals
Great course with good examples, concise and to the point! I had one week to Upskill my knowledge of Kotlin and SpringBoot (already familiar with SpringBoot), before starting at a new position as a Senior Developer.
Joseph Sterling Grah, a student

Listed as All Levels, but it needs working Java, Spring Boot and Maven or Gradle experience first.

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What you will learn

  • Kotlin Programming Language and its benefits
  • Write Code using Kotlin Programming Language
  • Building Applications using Kotlin
  • Build RestFul Services using SpringBoot and Kotlin
  • Test Kotlin using JUnit5
  • Kotlin and Java Interoperability
  • Integrate Spring Data JPA with Kotlin
  • Integration testing DB Layer using TestContainers & JUnit5
  • Unit Testing Functions calls using Mockk Library

Course content

21 sections · 93 lectures · 8.4 hours of video 4 assignments, 2 articles

  1. 1Getting Started with the Course 2 free previews2 lectures · 3 min
  2. 2Course Slides & Source Code2 lectures
  3. 3Getting Started with Kotlin Programming Language 2 free previews2 lectures · 7 min
  4. 4Kotlin Fundamentals8 lectures · 39 min
  5. 5Functions in Kotlin3 lectures · 21 min
  6. 6Classes, Interfaces and Inheritance16 lectures · 1 quiz · 1.3 hours
  7. 7Nulls in Kotlin3 lectures · 19 min
  8. 8Collections, Arrays & Lamda Expressions9 lectures · 1.2 hours
  9. 9Exceptions In Kotlin1 lecture · 7 min
  10. 10Scope Functions4 lectures · 27 min

Who it is for

The instructor says it suits

  • Developers who are interested in learning Kotlin Programming language
  • Developers who are interested in building applications using Kotlin and SpringBoot
  • Java developers who would like to learn Kotlin Programming Language

What you need before you start

  • Java 11 or Higher is Required
  • Experience working with any IDE( Intellij, Eclipse)
  • Experience working with Java
  • Experience building application using SpringBoot
  • Gradle or Maven Build tool Experience is must

How it compares

Against the other 28 rated Udemy courses in Kotlin on CourseDuck:

  • Rating4.4 out of 5higher than 25% of them
  • Reviews1,485#9 of 29 by number of reviews
  • Length8.4 hoursshorter than 60% of them
  • Last updatedFebruary 2026more recently than 85% of them

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Course Description

Kotlin is the Modern, concise and safe programming language and  is one of the popular JVM language in this day and age.

It’s also interoperable with Java and other languages, and provides many ways to reuse code between multiple platforms for productive programming.

This course will focus on using Kotlin for Server-Side Development using SpringBoot framework. This is a pure hands-on oriented course which covers these two topics:

  • Covers Kotlin Fundamentals thats necessary for Java Developers

  • Build RestFul APIs using SpringBoot and Kotlin

Section 1: Getting Started With the Course

  • This section covers the course objectives and the prerequisites that are needed to make the most out of this course.

Section 2: Getting Started with Kotlin Programming Language

  • In this section, I will introduce you to Kotlin Programming Language and why its a powerful language for enterprise development.

    • Introduction to Kotlin

    • How Kotlin Works with the JVM?

Section 3: Kotlin Fundamentals

  • In this section, we will explore the fundamentals of Kotlin.

    • val & var variables in Kotlin

    • Basic Types - Int, Long, Double, String

    • Conditionals - If and when block

    • Ranges , Loops

    • while & do-While

    • break, labels and return

Section 4: Functions in Kotlin

  • In this section, we will learn about functions in Kotlin and different ways of declaring and using them

    • Defining and Invoking Functions

    • Default Value Parameters & Named Arguments

    • Top-Level Functions and Top-level Properties

Section 5: Classes, Interfaces and Inheritance

  • In this section, we will learn about classes, inheritance and interfaces in detail.

    • Introduction to class - Creating a class and objects

    • Primary Constructors

    • Secondary Constructors

    • initializer code using init block

    • Data Classes

    • Custom Getters and Setters

    • Inheritance - Extending Classes

    • Inheritance - Override Functions, Variables

    • object keyword for creating instance of the class

    • companion object Keyword

    • Interfaces

    • Interfaces - Handling Conflicting Functions

    • Interfaces - Defining and Overrding Variables

    • Visibility Modifiers

    • Type Checking, Casting and Smart Cast

    • Enum class

Section 6: Nulls in Kotlin

  • In this section, we will learn about handling nulls in Kotlin

    • Nullable & Non-Nullable types in Kotlin

    • Safe Call(?) , Elvis Operator(?:) & Non Null Assertion(!!) to deal with Null Values

    • Invoking or assigning a Nullable Type to a Non-Nullable Type

Section 7: Collections, Arrays & Lamda Expressions

  • In this section, I will introduce you to collections, arrays and lambda expressions in Kotlin

    • Introduction to Collections

    • Introduction to Lamda Expressions

    • Lambdas and Higher Order Functions

    • Filter Operations on Kotlin Collections

    • Map Operations on Kotlin Collections

    • FlatMap Operations in Collections

    • Working With HashMaps

    • Lazy Evaluation of Collections using Sequences

    • Nullability in Collections

Section 8 : Exceptions In Kotlin

  • In this section, I will cover the exceptions in kotlin and the techniques to handle them.

    • Handling Exceptions using try-catch

Section 9 : Scope Functions

  • In this section, I will introduce you all to scope functions in Kotlin and its usage.

    • Introduction to Scope Functions

    • apply & also Scope Function

    • let Scope Function

    • with & run Scope Function

Section 10 : Getting Started with Kotlin and Spring Boot

  • In this section, I will explain the overview of the app we are going to build and build a very simple API.

    • Overview of the app & Project Setup

    • Build a Simple Endpoint - Greeting Controller

    • Constructor Injection in Spring

    • Setting up different profiles in Spring Boot

    • Set up Logging in Kotlin

Section 11 : Integration/Unit Testing using Junit 5

  • In this section, I will code and explain about the techniques to write different types of test cases using spring boot and Kotlin.

    • Introduction to Automated Tests & Setting up JUnit5

    • Integration Test for Controller

    • Unit Test for Controller - Using the Mockk Mocking library

Section 12 : Build the Course Catalog Service

  • In this section, we will build the Course Catalog Service to manage the Courses

    • Set up the Course Entity & CourseDTO

    • Create CourseRepository & Configure JPA in application.yml file

    • Build the POST Endpoint for adding new Course I

    • ntegration test for the POST endpoint using JUnit5

    • Build the Get Endpoint to retrieve all Courses

    • Integration test for the GET endpoint to retrieve all the courses

    • Build the Update Endpoint to update a Course

    • Integration test for the PUT endpoint using JUnit5

    • Build the DELETE endpoint to delete a Course

Section 13: Unit Testing Controller layer (Web Tier)

  • In this section, we will code and learn about how to write unit tests for the controller

    • Setting up the Unit Test for the CourseController

    • Unit test for the Post Endpoint in CourseController

    • Unit test for the GET Endpoint in CourseController

    • Unit test for the PUT Endpoint in CourseController

    • Unit test for the DELETE Endpoint in CourseController

Section 14 : Bean Validation using Validators and ControllerAdvice

  • In this section, we will code and learn the different techniques to apply bean validations and handle exceptions using the ControllerAdvice Pattern

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Instructor Details

Pragmatic Code School

Pragmatic code school's primary goal is to provide technical training through a practical approach.

The courses are completely hands-on oriented and cover different techniques and patterns that are used in enterprise development standards

Each course explains the concepts by building applications which will give an experience of building a real enterprise application.

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COURSES ROADMAP:  |

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Course roadmap to enroll in the Kafka Courses.

For Experienced Kafka Developers:

1. Apache Kafka for Developers using Spring Boot[LatestEdition]

2. Kafka Streams API For Developers using Java/SpringBoot 3.X

3. Kafka for Developers - Data Contracts using Schema Registry

For Kafka Beginners:

1. Apache Kafka for Beginners - Learn Kafka by Hands-On

2. Apache Kafka for Developers using Spring Boot[LatestEdition]

3. Kafka Streams API For Developers using Java/SpringBoot 3.X

4. Kafka for Developers - Data Contracts using Schema Registry


Course roadmap to enroll in the Modern Java Courses.

1. Modern Java - Learn Java 8 features by coding it

2. Multithreading,Parallel & Asynchronous Coding in Modern Java


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Reviews

4.4

1,485 ratings on Udemy

Select a bar to show only those reviews.Select the bar again to show every rating.

By Kushal Karamchandani on 2/22/2026

very informative. A lot of the code was already available from the zip file. For me personally, it was more fun to code along and take some time getting familiar with the codebase rather than just having a few coding assignments. I noticed in one instance a student had written a course adding function in an integration unit test, indicating that maybe not everyone is working along 100%

By Joseph Sterling Grah on 9/18/2025

Great course with good examples, concise and to the point! I had one week to Upskill my knowledge of Kotlin and SpringBoot (already familiar with SpringBoot), before starting at a new position as a Senior Developer. And I am glad I chose this course! Thank You

By Samuel Tavares Da Silva on 4/15/2025

The course starts with the fundamentals without spending too much time on them. It delivers a lot of valuable information, including not only abstract concepts but also a complete, real-world example with all the necessary support and resources to grasp the most important topics.

By Anonymized User on 1/9/2025

Overall, the review was positive. However, it could be enhanced by including a dedicated section for setting up PostgreSQL on macOS for users not using Docker. Additionally, providing a basic tutorial on Docker would be beneficial, enabling users to proceed with the setup more confidently.

By ALEXANDRE A BARBOSA on 3/27/2024

Dilip is absolutely fantastic! His ability to delivery key information precisely when needed, catering to various skills levels and technologies, truly impressived me. I am eargely antecipating his next advanced Kotlin + Spring Boot course. With Dilip's extensive experience, evident throughout this course, I wouldn't hesitate to choose his instruction again.

By Mikko Luhtasaari on 3/12/2024

Goes through the basics but at times there seems to be a weird focus on irrelevant details and that makes it difficult to focus on the relevant stuff. You'll get the same knowledge from a couple of getting started tutorials from the official docs.

By Peter Anyaduba on 6/22/2023

My IntelliJ is IntelliJ IDEA 2023.1.2 (Community Edition) Build #IC-231.9011.34, built on May 16, 2023 Runtime version: 17.0.6+10-b829.9 aarch64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o. My System is macOS 12.3 GC: G1 Young Generation, G1 Old Generation Memory: 16GB Cores: 10 Metal Rendering is ON Kotlin: 231-1.8.21-IJ9011.34 I was able to scale through even though my IntelliJ was slightly ahead of the trainer's IntelliJ. I didn't find it difficult to follow.

By Amit Siwach on 4/20/2023

They Try to covered all impotent topics within minimum time... this course is ok for those who have good experience in Java, SpringBoot, JPA, Docker, Junit5. Some Topics they try to finish very quickly .... Thats Why we have to give more time to understand clearly...overall it will give you confidence after completing successfully to develop first Rest api In Kotlin. Go for it But don't expect much from this course.

By M. H. on 2/25/2023

The course was really helpful especially the spring content. The instructor, Dilip, is really good at explaining the topics. He is really committed to his course and in helping someone out if there are any problems with the understanding of topics or if you have any additional questions. Here and there are some minor issues but that doesn't really matter. It's definitly worth it's price.

By N A on 8/4/2022

The Good: - clear explanations - covers pretty much everything I needed for working generally with spring boot. - covers the whole dev for an app - dev + testing (unit + ITTest) - definitely excellent for those that come from a java + spring boot background - might be tricky for those that dont. - great demonstration for how spring boot and kotlin can be used together. Bad: - the only thing i can think off is that not every kotlin feature is covered

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Quality Score

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Overall Score : 88 / 100