About

This is a simple Kotlin & Spring Boot backend CRUD app.

Development Notes

Kotlin

• Statically typed (type checking done by compiler during compile time) programming language running on JVM (JVM isn’t compulsory for the reason below)
• Can be compiled to JS or native code (ahead-of-time compilation, AOT) using Kotlin/Native
• Kotlin/Native is a technology for compiling Kotlin code to native binaries, which can run directly on hardware without the need for a virtual machine
• Kotlin Code -> Java Bytecode -> JVM

Kotlin for Backend

• Technologies that enable Kotlin to be used as backend
• Spring Boot
• Ktor
• Vert.x
• Micronaut
• Exposed (This is more of a database technology)
• The above technology (except exposed) support standalone backend development

Spring & Spring Boot

• Spring is a comprehensive framework that provides a wide range of features for building enterprise-level applications, requiring manual configuration and setup.
• Spring Boot builds on top of Spring, offering auto-configuration, embedded servers, and production-ready features to simplify and accelerate the development and deployment of Spring applications. It reduces the complexity and boilerplate code associated with traditional Spring applications, making it easier to get started and maintain.

Creating a new Spring Boot application

• Using Spring Initializer
• Using IDEs eg. Eclipse & IntelliJ IDEA
• Using Spring Boot CLI

Maven Vs Gradle

• Both are build automation tools
• Maven is XML based (less flexible)
  • .pom file for configuration
  • Convention over configuration
  • Convention over Configuration (CoC) is a software design principle that aims to reduce the number of decisions developers need to make by following a set of predefined conventions.
• Gradle is Groovy/Kotlin based (more flexible)
  • build.gradle or build.gradle.kts for configuration
• Uses Groovy or Kotlin DSL (Domain Specific Language)

Using Spring Initilizr (Web)

JAR vs WAR packaging

• Packaging in refers to the process of bundling all the components of a software application into a single file or set of files that can be easily distributed and deployed.
• JAR files are used for general-purpose Java applications and libraries, while WAR files are specifically designed for web applications and include additional structure and configuration needed for deployment on web servers.
• For a typical backend application, especially one built with Spring Boot, use JAR packaging. It offers flexibility, ease of deployment, and aligns well with modern deployment practices.

Feature Topics

• CRUD operation
• Setting-up development/production/qa environments
• Authentication & authorisation
• Kotlin Coroutines
• Connectivity with Different DBs(MySQL, Postgres, MongoDB)
• Unit test
• Integration test
• Containerisation
• Deployment

Controller Class

• Controller classes act as an intermediary between the user interface (external requests) and the application's business logic.
• They handle incoming HTTP requests and return response to the client.
• Annotated with @RestController or @Controller to indicate Spring controller
  • @RestController is a specialization of @Controller that automatically applies @ResponseBody to all methods (meaning return values are written directly to the HTTP response body)

Service Class

• A service class is used to encapsulate business logic and interact with repositories.
• A service is used by controller.
• Acts as a middle layer between controllers and repositories or other data source
• Annotated with @Service