(Moshi in kotlin) #Json vs #field:Json - json

Question

Serialization does not happen properly when I use #Json in the fields but it started working after changing to #field:Json.
I came through this change after reading some bug thread and I think this is specific to kotlin. I would like to know what difference does #field:Json bring and is it really specific to kotlin?

Answer 1

Whatever you put between # and : in your annotation specifies the exact target for your Annotation.
When using Kotlin with JVM there is a substantial number of things generated, therefore your Annotation could be put in many places. If you don't specify a target you're letting the Kotlin compiler choose where the Annotation should be put. When you specify the target -> you're in charge.
To better see the difference you should inspect the decompiled Java code of the Kotlin Bytecode in IntelliJ/Android Studio.
Example kotlin code:
class Example {
#ExampleAnnotation
val a: String = TODO()
#get:ExampleAnnotation
val b: String = TODO()
#field:ExampleAnnotation
val c: String = TODO()
}
Decompiled Java code:
public final class Example {
#NotNull
private final String a;
#NotNull
private final String b;
#ExampleAnnotation
#NotNull
private final String c;
/** #deprecated */
// $FF: synthetic method
#ExampleAnnotation
public static void a$annotations() {
}
#NotNull
public final String getA() {
return this.a;
}
#ExampleAnnotation
#NotNull
public final String getB() {
return this.b;
}
#NotNull
public final String getC() {
return this.c;
}
public Example() {
boolean var1 = false;
throw (Throwable)(new NotImplementedError((String)null, 1, (DefaultConstructorMarker)null));
}
}
For more info go to Kotlin docs.