ZIO CLI Framework: Common Problem Solving Methods for Command Line Application Development in Java Class Libraries
ZIO CLI Framework: Solutions to Common Problems in Command Line Application Development in Java Class Libraries
Abstract: ZIO CLI is a command-line application development framework based on the ZIO functional programming library. It provides a simple, flexible, and composable way to build command-line applications. This article introduces some common problems and their solutions in the ZIO CLI framework, and provides relevant Java code examples.
How to parse command line parameters?
The ZIO CLI framework provides a set of functions to help parse command-line parameters. You can create a command line application using the 'Args. command' function and define command line parameters using the 'Args. argument' and 'Args. option' functions. Here is a simple example:
import zio.cli.Args;
import zio.cli.HelpDoc;
public class MyApp {
public static void main(String[] args) {
Args.command("myapp", "My application", runProgram()).parse(args).getOrElseThrow();
}
public static Args<HelpDoc> runProgram() {
return Args.argument("name", "Name of the user")
.map(name -> "Hello, " + name + "!")
.flatMap(message -> Args.succeed(() -> System.out.println(message)));
}
}
In the above example, we defined a command-line application called 'myapp', which takes a parameter named 'name' and outputs' Hello, name! '. By calling the 'parse' method, we can parse command line parameters and use the 'getOrElseThrow' method to process the parsing results.
How to handle subcommands?
The ZIO CLI framework supports processing subcommands for command-line applications. You can use the 'Args. command' and 'Args. subcommand' functions to define subcommands. Here is an example:
import zio.cli.Args;
import zio.cli.HelpDoc;
public class MyApp {
public static void main(String[] args) {
Args.command("myapp", "My application", runProgram()).parse(args).getOrElseThrow();
}
public static Args<HelpDoc> runProgram() {
return Args.subcommand("greet", "Greet command", greetProgram());
}
public static Args<HelpDoc> greetProgram() {
return Args
.argument("name", "Name of the user")
.map(name -> "Hello, " + name + "!")
.flatMap(message -> Args.succeed(() -> System.out.println(message)));
}
}
In the above example, we defined a command-line application called 'myapp', which has a subcommand called 'greet'. The subcommand 'greet' takes a parameter named 'name' and outputs' Hello, name! '. By calling the 'parse' method, we can parse command line parameters and execute corresponding processing logic according to the command.
3. How to handle option parameters?
The ZIO CLI framework can help parse option parameters for command-line applications. You can use the 'Args. option' function to define option parameters, and use the 'Args. withDefault' function to provide default values for option parameters. Here is an example:
import zio.cli.Args;
import zio.cli.HelpDoc;
public class MyApp {
public static void main(String[] args) {
Args.command("myapp", "My application", runProgram()).parse(args).getOrElseThrow();
}
public static Args<HelpDoc> runProgram() {
return Args
.option(
Args.longOption("count"),
Args.helpDoc("Count option"),
Args.intArg("COUNT"))
.withDefault(0)
.map(count -> "Count: " + count)
.flatMap(message -> Args.succeed(() -> System.out.println(message)));
}
}
In the above example, we defined a command-line application called 'myapp' that accepts an option parameter called 'count'. The option parameter 'count' is an integer type and has a default value of 0. By calling the 'parse' method, we can parse command line parameters and use the 'getOrElseThrow' method to process the parsing results.
Conclusion:
Through the ZIO CLI framework, we can easily build flexible and composable command-line applications. Using the functions mentioned above, we can parse command line parameters, process subcommands, and process option parameters. These examples provide a convenient guide to getting started with developing Java command-line applications using the ZIO CLI framework.
Appendix: Resources and links related to the ZIO CLI framework:
-Official document: https://zio.github.io/zio-cli/
-GitHub repository: https://github.com/zio/zio-cli
