ZIO CLI framework: creating interactive command-line applications in Java class libraries
ZIO CLI framework: creating interactive command-line applications in Java class libraries
ZIO CLI is a command-line interface (CLI) framework built on the ZIO functional programming library, which allows developers to easily create interactive command-line applications. As a powerful Java class library, ZIO CLI provides a simple and flexible way to handle command line parameters, execute commands, and respond to user input.
The core concepts of ZIO CLI are commands and options. Commands represent specific actions that an application can perform, while options are used to configure these actions. Developers can define their own commands, specify some flags, and specify the properties of options through annotations. This makes building command based applications very simple.
The following is an example of building an interactive command-line application using the ZIO CLI framework:
import zio.*;
import zio.cli.*;
import zio.console.Console;
import zio.console.Console.Live;
import java.util.List;
public class MyCLIApp {
public static void main(String[] args) {
List<Command<MyCLIEnv>> commands = List.of(
new Command<>("hello")
.withDescription("Say hello to someone")
.withOptions(Options.<String>argument("name", "The person to greet")
.required()
.validate(Validation.hasText()))
.mapCmd((name) -> sayHello(name))
);
ZManaged.environment().flatMap(env ->
ZIO.fromOption(Command.build(args, commands))
.flatMap(cmd -> cmd.fold(
help -> ZIO.succeed(0),
cmdFunc -> {
MyCLIEnv myCLIEnv = env.getOrElseThrow(() -> new IllegalStateException("Missing CLI environment"));
return cmdFunc.apply(myCLIEnv);
}
))
).orDie().exitCode();
}
private static ZIO<MyCLIEnv, Throwable, Integer> sayHello(String name) {
return console().putStrLn("Hello, " + name + "!").exitCode();
}
private static Console.Service console() {
return new Live();
}
static record MyCLIEnv(Console.Service console) {
public static MyCLIEnv fromServicesZManaged(ZManaged<Console, Throwable, Console.Service> console) {
return new MyCLIEnv(console.orDie());
}
}
}
In the above code, we used the ZIO CLI framework to create a command called 'hello'. This command accepts an option called 'name' to specify the person to greet. In the command implementation, we simply print the person's name to the console.
Then, we use the 'Command. build' method in the 'main' function to parse command line parameters and execute the corresponding command function based on the parsing results. Note that the 'mapCmd' method is used to convert the input type of the command function from 'List<String>' to 'String' to adapt to the specific command function we define.
Finally, we execute the entire ZIO program through the 'ZIORuntime' and use the returned 'ExitCode' as the exit code of the program.
Through the ZIO CLI framework, we can easily build interactive command-line applications and define the specific functions of the application by defining commands and options. At the same time, ZIO's functional programming capabilities also provide us with powerful error handling, concurrency, and resource management capabilities, making developing command-line applications easier to maintain and expand.
