jakarta.validation-api with picocli

[ashr123]

is there a way to use jakarta.validation-api with plain picocli (without Springboot/Hibernate etc.)? it may be silly but I'm trying to use it as it is but is doesn't work.
Example:

@CommandLine.Parameters(description = "Is to show sum calculation? (values: true, false)")
private boolean isDetailed;
@Positive
@CommandLine.Parameters(description = "How many roles should the program make?")
private long roles;
@Min(3)
@CommandLine.Parameters(description = "Used to tell the number of side the dice has.")
private int d;
@PositiveOrZero
@CommandLine.Parameters(
		description = "Used to be added per role.",
		defaultValue = "0"
)
private int constantAddition;

[remkop]

I suspect that is not possible but you can ask the maintainers of the jakarta.validation-api project, they may be better positioned to answer that question.

[ashr123]

@remkop I see that hibernate-validator is an implementation that uses validation but there is need to create Validator (see https://docs.jboss.org/hibernate/validator/8.0/reference/en-US/html_single/#_validating_constraints) can this integrate dynamically to picocli (i.e. recognize the existence of hibernate-validator and initiate a Validator)?
Maybe it can be used in picocli.CommandLine#executeUserObject

[remkop]

There are several ways to think about this.
I don't plan on adding built-in support for jakarta.validation-api to the picocli library.

However, the example in the user manual (calling a helper method from the run method) is only one way to accomplish this.

Perhaps a nicer way is to have a custom IExecutionStrategy which does the validation before executing the command.

Such a custom IExecutionStrategy could look something like this:

class ValidatingExecutionStrategy implements IExecutionStrategy {
    public int execute(ParseResult parseResult) {
        validate(parseResult.commandSpec());
        return new CommandLine.RunLast().execute(parseResult); // default execution strategy
    }

    void validate(CommandSpec spec) {
        Validator validator = Validation.buildDefaultValidatorFactory().getValidator();
        Set<ConstraintViolation<Object>> violations = validator.validate(spec.userObject());
        if (!violations.isEmpty()) {
            String errorMsg = "";
            for (ConstraintViolation<?> violation : violations) {
                errorMsg += "ERROR: " + violation.getMessage() + "\n";
            }
            throw new ParameterException(spec.commandLine(), errorMsg);
        }
    }
}

The application would wire it in like this:

    public static void main(String[] args) {
        MyApp app = new MyApp();
        new CommandLine(app)
                .setExecutionStrategy(new ValidatingExecutionStrategy())
                .execute(args);
    }

I have added this example to the user manual (the HTML will be published with the next release),
and updated the java examples
and added a kotlin example.

[ashr123]

@remkop thanks 😃
eventually I went with the following code:

Logger.getLogger("org.hibernate").setLevel(Level.OFF);
final CommandLine commandLine = new CommandLine(DiceRoller.class);
CommandLine.IExecutionStrategy executionStrategy = commandLine.getExecutionStrategy();
commandLine.setExecutionStrategy(parseResult ->
		{
			try (ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory())
			{
				Set<ConstraintViolation<Object>> violations = validatorFactory.getValidator().validate(parseResult.commandSpec().userObject());
				if (!violations.isEmpty())
				{
					final StringBuilder errorMsg = new StringBuilder();
					for (ConstraintViolation<?> violation : violations)
						errorMsg.append("ERROR: ").append(violation.getPropertyPath()).append(' ').append(violation.getMessage()).append(System.lineSeparator());
					throw new CommandLine.ParameterException(parseResult.commandSpec().commandLine(), errorMsg.toString());
				}
			}
			return executionStrategy.execute(parseResult);
		})
		.execute(args);