Accidental override when using custom exception and extending RuntimeException and implementing GraphQLError in kotlin

Support
1

I have a custom exception class which extends RuntimeException and implements GraphQLError. There is a conflict between the message attribute in RuntimeException and getMessage() in GraphQLError. I see a post where this was mentioned in the past. Issue - 7658. Is there a resolution for this issue?
The getter setter generated for message property in RuntimeException is in conflict with the method getMessage() in GraphQLError. How do we work around this. Any suggestions please. Thanks.

2

I don’t think you can. How would you work around this in Java? If you had a Java class that extended RuntimeException and also implemented GraphQLError, and you called getMessage() on that class, what would happen? If the function signatures are the same…

3

Thanks for the reply. I think this is because how kotlin treats properties of a class vs methods (from what I searched). The RuntimeException has a method getMessage() which kotlin exposes as a property message. GraphQLError itself has an abstract method getMessage(), and Kotlin automatically generates a getter for the message property (getMessage()), which causes a conflict because both message and getMessage() end up with the same JVM signature . Java does not treat the properties of a class like kotlin does.

4

I had to work around this by using a java class alongside kotlin (as suggested in the other post). Thanks.

5

Yeah but in Java code, RuntimeException extends Exception which extends Throwable, and Throwable has a method called getMessage(). So if you tried this in Java, you’d have a class that inherits getMessage() from Throwable, but also wants to implement getMessage() from the GraphQLError interface. idk how you resolve that in Java code.

My point is that I don’t think this would work in Kotlin OR Java.

6

This is my java class. And then my custom exception (kotlin) extends this BaseException class. This works.

public abstract class BaseException extends RuntimeException implements GraphQLError {
abstract String errorMessage() ;
@Override
public String getMessage() {
return errorMessage();
}
@Override
@JsonIgnore
public StackTraceElement getStackTrace() {
return super.getStackTrace();
}
}

7

I actually don’t understand how that works. I would have expected the Java compiler to complain about it.

I guess it’s not possible in Kotlin… because it tries to generate the getter for the field, which results in the same method being defined twice in the Java code.

The only thing that might be possible is to mark message with @JvmField, which prevents the Kotlin compiler from generating getters and setters for the field. But I think that’s impossible, since it’s an inherited field, and it’s syntactic sugar anyway.

8

You are right about @JvmField. I tried that and it complains that it cannot be used on inherited fields. But you should try this. Java base class and kotlin extending the base class. It works for me, have tested it.

9

I believe you that it works, I just don’t understand how… Java be crazy.