Spring Shell with Spring Boot Tutorial

Introduction to Spring Shell

Spring Shell is a subproject of the Spring Framework that provides an interactive shell for Spring applications. It allows developers to create command-line interfaces (CLIs) with ease, enabling quick interaction with their application. Spring Shell's command execution is based on the Spring Bean lifecycle, making it a powerful tool for managing applications.

Setting Up the Project

To get started with Spring Shell in a Spring Boot application, you need to set up a new Spring Boot project. You can do this using Spring Initializr or manually.

Using Spring Initializr

Visit Spring Initializr and configure your project with the following settings:

• Project: Maven Project
• Language: Java
• Spring Boot: 2.5.0 or later
• Dependencies: Spring Shell, Spring Boot DevTools

Once you have configured your project, click on Generate to download the project.

Adding Spring Shell Dependency

If you created your project manually, ensure you include the Spring Shell dependency in your pom.xml file:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-shell</artifactId>
</dependency>

Creating Your First Command

Let's create a simple command that greets the user. First, create a new class called GreetingCommand.java in your resource folder.

import org.springframework.shell.standard.ShellComponent;
import org.springframework.shell.standard.ShellMethod;

@ShellComponent
public class GreetingCommand {

    @ShellMethod("Greet the user")
    public String greet(String name) {
        return "Hello, " + name + "!";
    }
}

In this code, we define a shell command that takes a name as a parameter and returns a greeting message.

Running the Application

To run your Spring Boot application, you can use the following command in your terminal:

Once the application starts, you will see the shell prompt. You can now test your command by typing:

Customizing the Shell

Spring Shell allows for customization of the shell environment. You can change the prompt, add colors, and more. Here’s how to customize the prompt:

import org.springframework.shell.standard.ShellComponent;
import org.springframework.shell.standard.ShellMethod;
import org.springframework.shell.standard.ShellOption;

@ShellComponent
public class CustomShell {

    @ShellMethod("Set custom prompt")
    public void setPrompt(@ShellOption(defaultValue = "MyShell") String prompt) {
        System.setProperty("spring.shell.interactive.prompt", prompt);
    }
}

This command allows you to set a custom prompt for your shell. You can call this method from the shell to change the prompt dynamically.

Conclusion

In this tutorial, we covered how to set up a Spring Boot application with Spring Shell, create commands, and customize the shell environment. Spring Shell provides powerful capabilities for building interactive command-line applications. You can explore further by adding more complex commands and integrating other Spring features.