Book Image

Building Applications with Spring 5 and Kotlin

By : Miloš Vasić
Book Image

Building Applications with Spring 5 and Kotlin

By: Miloš Vasić

Overview of this book

Kotlin is being used widely by developers because of its light weight, built-in null safety, and functional and reactive programming aspects. Kotlin shares the same pragmatic, innovative and opinionated mindset as Spring, so they work well together. Spring when combined with Kotlin helps you to reach a new level of productivity. This combination has helped developers to create Functional Applications using both the tools together. This book will teach you how to take advantage of these developments and build robust, scalable and reactive applications with ease. In this book, you will begin with an introduction to Spring and its setup with Kotlin. You will then dive into assessing the design considerations of your application. Then you will learn to use Spring (with Spring Boot) along with Kotlin to build a robust backend in a microservice architecture with a REST based collaboration, and leverage Project Reactor in your application. You’ll then learn how to integrate Spring Data and Spring Cloud to manage configurations for database interaction and cloud deployment. You’ll also learn to use Spring Security to beef up security of your application before testing it with the JUnit framework and then deploying it on a cloud platform like AWS.
Table of Contents (12 chapters)

Using Project Reactor

It is time to update our REST API so that it becomes an event-driven application. You will see that the changes we make are not difficult to apply. We will start by updating our dependencies so that Project Reactor classes are accessible. Open your API application build.gradle configuration and extend it:

...  
dependencies { 
    ...  
    compile 'io.projectreactor:reactor-bus:2.0.8.RELEASE' 
    ...  
} 
...  

Here, we introduced support for a Project Reactor bus. We will use it to trigger an action in some particular situations. We will email the system administrator if the number of total Notes or TODOs in the system reaches a critical level. This example is trivial. One good example would be triggering actions when storage reaches a significant number of sold items. Another could be if the number of unsubscribed users increases more than a...