Custom Commands in Spring Shell
Introduction
Spring Shell is a powerful framework enabling the development of CLI (Command Line Interface) applications. One of its key features is the ability to create custom commands to extend functionality. This tutorial will guide you through creating, using, and testing custom commands in Spring Shell.
Setting Up Spring Shell
Before we start defining custom commands, ensure that you have a Spring Boot application setup. You can initialize a project using Spring Initializr. Include the following dependency:
spring-boot-starter-shell
Once your project is set up, you can start creating your custom commands.
Creating a Custom Command
To create a custom command, you need to define a method in a Spring-managed bean and annotate it with @ShellMethod. Here’s a simple example:
import org.springframework.shell.standard.ShellComponent;
import org.springframework.shell.standard.ShellMethod;
@ShellComponent
public class MyCommands {
@ShellMethod("Say hello")
public String hello() {
return "Hello, World!";
}
}
In this example, we created a command called hello that outputs "Hello, World!".
Running the Command
After defining your command, you can run your Spring Boot application. Open your terminal and type the following command:
./mvnw spring-boot:run
Once the application is running, type hello in the shell prompt:
hello
Hello, World!
Adding Parameters to Commands
You can also add parameters to your commands. Here’s how to modify the previous example to accept a name parameter:
@ShellMethod("Say hello with a name")
public String hello(String name) {
return "Hello, " + name + "!";
}
Now, you can call the command with a name:
hello John
Hello, John!
Creating Command Options
You can also define options for your commands using the @ShellOption annotation. Here’s an example:
@ShellMethod("Greet with options")
public String greet(@ShellOption(defaultValue = "User") String name) {
return "Hello, " + name + "!";
}
In this example, if no name is provided, it defaults to "User". You can run the command like this:
greet
Hello, User!
Conclusion
Custom commands in Spring Shell allow you to extend the functionality of your CLI applications easily. By following the steps outlined in this tutorial, you can create commands that accept parameters and options, enhancing the user experience. Experiment with different commands and options to fully utilize Spring Shell's capabilities.