Spring Shell: required Boolean with non-default value

Question

spring shell version: 3.1.6

In one of my commands, I want to make sure that the end-user specifically indicates whether they either want A or B by using a Boolean. I don't want to make the choice for the end user.

When I add the following @Option on my command:

@Option(required = true, description = "Description", longNames = "Some long name")  Boolean booleanOption

Spring Shell, automatically transforms the booleanOption to defaultValue false. The help menu of the command indicates that the booleanOption is optional.

When transforming into

@Option(required = true, description = "Description", longNames = "Some long name")  boolean booleanOption

Still, the help menu indicates the booleanOption as optional. I assume for 2 reasons that this should not be the case: (1) it is a boolean and not Boolean. (2) required is explicitly set to true. The defaultValue is again false.

Setting the defaultValue to 'true' explicitly seems to be working.

@Option(required = true, description = "Description", longNames = "Some long name", defaultValue = "true")boolean booleanOption

It will show that the boolean is optional, but the default value will be true.

But again, I didn't want to choose for the user. I want the end user to articulate their choice when doing a command specifically.

If I write:

@Option(required = true, description = "Description", longNames = "Some long name", defaultValue = "")Boolean booleanOption

Or

@Option(required = true, description = "Description", longNames = "Some long name", defaultValue = "null")Boolean booleanOption

The defaultValue still translates to false (while as a Boolean I would expect it to be able to be null).

Is this the intended behavior? Is there a way to make this work?

Answer 1

Looks like this is by design org.springframework.shell.command.annotation.support.CommandRegistrationFactoryBean:

else if (ClassUtils.isAssignable(boolean.class, parameterType)){
    optionSpec.required(false);
    optionSpec.defaultValue("false");
}

I guess this is a side-effect of:

Boolean types are usually used as flags meaning argument value may not be needed

https://docs.spring.io/spring-shell/docs/current/docs/index.html#boolean

A possible "workaround" might be to add your own Boolean Enum and use that instead of boolean:

enum MyBoolean
{
    false,
    true
}