public final class CommandLine

Parses a command line into an annotated command and runs it.

A command is a class annotated Command that implements Runnable or java.util.concurrent.Callable<Integer>. Its fields annotated Option and Parameters receive the arguments:

@Command(name = "greet", mixinStandardHelpOptions = true, version = "greet 1.0",
        description = "Prints a greeting.")
public class Greet implements Runnable {
    @Option(names = {"-n", "--count"}, description = "How many times.",
            defaultValue = "1")
    private int count;

    @Parameters(paramLabel = "<name>", description = "Who to greet.")
    private String name;

    public void run() {
        for (int i = 0; i < count; i++) {
            System.out.println("Hello " + name);
        }
    }
}

The names follow picocli, so a picocli command usually needs only its imports changed. Unlike picocli nothing is read by reflection: the build reads the annotations and generates the parser’s bindings, so a mistake in a declaration is a build error, and the command runs the same on the JVM and as a native executable.

The build also writes main. With one top-level command it runs that command; with several, they become the subcommands of one named after the application. In a backend that also has controllers, the server is the serve subcommand and the command line with no arguments still starts it.

Exit codes: 0 for success, the command’s own code from a Callable, 1 when the command throws, 2 for a command line that does not parse.