This project is designed to show step by step how to migrate from Java to Kotlin with Spring Boot step by step:

• Step 0: Initial Java project
• Step 1: Java to Kotlin
• Step 2: Spring Boot 2
• Step 3: Spring WebFlux
• Step 4: Kotlin routing DSL

See Spring Kotlin support documentation for more details.

Code:

• No more semicolon at end of lines
• Type suffixed with colon, as statically typed as Java, optional type inference
• Show how to configure return type inference hints
• Short syntax for declaring properties and initializing them from the primary constructor instead of super verbose mostly auto-generated POJO
• Data classes
• Data classes
• Syntax help using naturally immutable classes
• : instead of extends
• No need for { } for empty classes / interfaces
• Optional parameter default value
• public by the default
• fun to declare functions
• Better lambdas: { } last parameter notation, lambda without collect, it default parameter
• Constructor without new
• main() top level method
• Utils class -> Kotlin extensions
• .getBody() -> .body
• Meaningful function names between backticks
• Show copy and paste Java to Kotlin

Build:

• Dependencies:
  • kotlin-stdlib-jre8
  • kotlin-reflect
  • jackson-module-kotlin
• Plugins:
  • kotlin
  • kotlin-spring
  • kotlin-noarg
• Configure to build Java 8 bytecode

Go to step 2: Spring Boot 2