原始类型的属性上不允许使用'lateinit'修饰符-Kotlin

Question

I'm getting an error while trying to assign a environment variable value to a lateinit variable. The error is "'lateinit' modifier is not allowed on properties of primitive types" .

My application.properties (reading the environment variable)

my.property.from.properties.file=true

MyService class:

@Component
class MyService @Autowired constructor(
    private val someService: SomeService) {

    @Value("\${my.property.from.properties.file}")
    private lateinit var myBooleanEnabled: Boolean

Assigning a value to it does not solve the problem. For example, with

private lateinit var myBooleanEnabled: Boolean = true

I get 2 errors:

• 'lateinit' modifier is not allowed on properties of primitive types
• 'lateinit' modifier is not allowed on properties with initializer

For what I read, I need a Delegated ( https://kotlinlang.org/docs/reference/delegated-properties.html ) but I could not grasp it fully. Also, I don't want to have to write another method to set the property if there is a "cleaner" solution. Any ideas?

Answer 1

The simplest thing is to define myBooleanEnabled as nullable and remove lateinit

private var myBooleanEnabled: Boolean? = null

In this case, it will not be interpreted as a primitive boolean in bytecode.

However, in your case, I'd suggest a constructor injection.

Answer 2

You can use constructor injection as shown below. If you're using Spring 4.3+ you don't need the @Autowired annotation. Spring documentation has some guidelines on this:

https://docs.spring.io/spring/docs/current/spring-framework-reference/languages.html#injecting-dependencies

@Component
class MyService(
    private val someService: SomeService,
    @Value("\${my.property.from.properties.file}")
    private val myBooleanEnabled: Boolean)