I will call this key combination from now on. In both cases, the code will be automatically converted. It is quite easy to use it: You can either open a Java class and press +++K, or you can copy a piece of code from Java file and paste it into the Kotlin one. IntelliJ has built-in support for converting Java classes to Kotlin. While the Kotlin Standard Library is not mandatory, it provides a huge number of useful functions for a small penalty in size. We have to register the Kotlin compiler plugin, apply it to the module, and add some dependencies. Id '' version '1.1.1'Ĭompile ':kotlin-stdlib:$kotlin_version' It means going from this: apply plugin: 'war' Add Kotlin to the Build Scriptīefore converting anything, add the Kotlin compiler to the build script. When you write Java code, you do not think about it too much, but Kotlin does things a bit differently. Proxies intercept calls to the object and enrich them with additional functionality.

A parameterless constructor is needed for instantiation, and the other two requirements are for making proxies. They mostly must be non-final with parameterless constructors and public methods. Java EE servers can be very picky about the way classes are structured. If you would like to run and test it, check the instructions on the GitHub. The project is in the jee/java directory. To get started, pull the fables-kotlin repo from GitHub. Our target for conversion is a simple Java WAR that can store and retrieve records from a database over a REST interface.

Luckily, all those issues can be avoided. Java EE and Kotlin are not really best friends unless you make them. Both of these and mandatory parameterless constructors will ruin attempts to write functional-style code.

Injection will introduce a lot of unnecessary null checks.

While most frameworks require non-final classes, Kotlin classes are final.

However, there are some subtle differences between the two that make conversion tricky:

As it is fairly easy to convert Java to Kotlin, it seems that making Java EE applications in Kotlin should be a no-brainer. One of the main strengths of Kotlin is good Java integration.

Converting kotlin to java