:exploding_head: I'm having trouble with Kotlin + ...

# spring

[Marian Schubert]

🤯 I'm having trouble with Kotlin + Spring magic (@Transactional) in following code:

class MyBoolean(var value: Boolean) {
    fun get(): Boolean = value
}

abstract class Foo {
    private val _hasError = MyBoolean(false)                                // <- line 16
    val hasError: Boolean get() = _hasError.get()
}

@Component
class MyFoo : Foo() {
    @Transactional
    fun doFoo() {
    }
}

class FooTest : SpringTest() {
    @Autowired
    lateinit var foo: MyFoo

    @Test
    fun `is null`() {
        assertThat(foo.hasError).isFalse                                    // <- line 33
        foo.doFoo()
    }
}

code/test above throws exception

java.lang.NullPointerException: Cannot invoke "com.bitsafe.behi.admin.projections.MyBoolean.get()" because "this._hasError" is null

at Foo.getHasError(FooTest.kt:16)
at <http://FooTest.is|FooTest.is> null(FooTest.kt:33)

which doesn't make sense as _hasError should never be null? If I remove @Transactional from doFoo method everything works as expected. What's going on?

BTW problem also disappears if I put stuff from abstract class Foo directly into class MyFoo (which I don't want).

[Chris Lee]

In the test foo is declared as lateinit - but not initialized.

[Chris Lee]

ah, its injected. perhaps put a breakpoint and see what things looks like.

[Marian Schubert]

good point with debugger

[Chris Lee]

hmmm. the generated proxy (for @Transactional) set it to null. is this a recent Spring version that would understand it’s a Kotlin class (with non-null semantics)?

[Marian Schubert]

Spring Boot 2.7.2 with Kotlin 1.7.10 and/or 1.6.21

[Chris Lee]

this link indicates that making the property open may address this. Are you using the Gradle koting/spring plugin to set objects to open? (this requires @Component on the classes to take effect)

[Marian Schubert]

ok if I change private val _hasError to open val _hasError it works

[Chris Lee]

cool. Adding @Component to the abstract class my also do it.

[Chris Lee]

(assuming the kotlin-spring plugin is in play)

[Marian Schubert]

yes adding @Component also fixed it. thanks a lot!

[sreich]

you may also wanna consider the all-open/spring plugin