What is Spring Boot CLI?

Spring Boot CLI (Command Line Interface) is a command-line tool provided by Spring Boot that allows developers to quickly create, run, and test Spring applications using simple commands.

It helps developers build Spring Boot applications faster without writing large amounts of configuration code or manually setting up complex project structures.

Spring Boot CLI internally uses Groovy and automatically configures many Spring Boot features, making development simple and productive.

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Definition of Spring Boot CLI

Spring Boot CLI is a tool that enables developers to run Spring Boot applications directly from the command line using Groovy scripts and minimal configuration.

It automatically handles dependency management, auto-configuration, and application startup.

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Why is Spring Boot CLI Used?

In traditional Spring development, developers needed to:

• Create Maven or Gradle projects manually
• Add dependencies one by one
• Configure XML or Java configuration files
• Set up application servers
• Write boilerplate code

This process consumed time and increased project complexity.

Spring Boot CLI simplifies development by allowing developers to:

• Run applications quickly
• Create prototypes faster
• Test ideas rapidly
• Reduce configuration effort
• Execute Spring Boot applications using simple commands

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Main Features of Spring Boot CLI

• Fast Spring Boot application development
• Command-line based execution
• Automatic dependency resolution
• Supports Groovy scripts
• Embedded server support
• Auto-configuration support
• Minimal setup required
• Rapid prototyping capability

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How Spring Boot CLI Works

Spring Boot CLI internally uses:

• Groovy language
• Spring Boot auto-configuration
• Embedded Tomcat server
• Dependency resolution mechanism

Developers write simple Groovy scripts, and Spring Boot CLI automatically:

• Detects dependencies
• Configures Spring Boot components
• Starts the embedded server
• Runs the application

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Installing Spring Boot CLI

Installation Using SDKMAN (Linux/macOS)

sdk install springboot

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Verify Installation

spring --version

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Example Output

Spring CLI v3.x.x

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Basic Spring Boot CLI Command

The main command used in Spring Boot CLI is:

spring run filename.groovy

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Simple Spring Boot CLI Example

Create File: app.groovy

@RestController
class HelloController {

    @GetMapping("/")
    String home() {
        return "Welcome to Spring Boot CLI";
    }
}

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Run the Application

spring run app.groovy

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Output

Spring Boot automatically starts the embedded server.

Open browser:

http://localhost:8080

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Browser Response

Welcome to Spring Boot CLI

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How Dependencies Work in Spring Boot CLI

One of the biggest advantages of Spring Boot CLI is automatic dependency detection.

For example:

• If @RestController is used, Spring Boot automatically adds Spring Web dependencies.
• If JPA annotations are used, Spring Boot automatically configures database-related dependencies.

This reduces manual dependency management.

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Adding Custom Dependencies

Developers can manually add dependencies using @Grab.

Example

@Grab("mysql:mysql-connector-java:8.0.33")

@RestController
class AppController {

    @GetMapping("/")
    String home() {
        return "MySQL Dependency Loaded";
    }
}

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Spring Boot CLI Commands

Command	Description
spring run	Runs Spring Boot application
spring test	Runs tests
spring init	Creates Spring Boot project
spring version	Displays Spring Boot version
spring help	Displays help information

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Using spring init Command

Spring Boot CLI can also generate Spring Boot projects using:

spring init myproject

This creates a new Spring Boot project automatically.

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Real-Time Example in Banking Application

Suppose a banking team wants to quickly prototype a REST API for account balance checking.

Using Spring Boot CLI, developers can create a working API within minutes.

Example

@RestController
class BankController {

    @GetMapping("/balance")
    String balance() {

        return "Available Balance: 50000";
    }
}

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Run Application

spring run bank.groovy

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Advantages of Spring Boot CLI

• Very fast development setup
• Minimal configuration required
• Automatic dependency handling
• Good for rapid prototyping
• Simple command-line execution
• Useful for learning Spring Boot
• Embedded server support
• Reduces boilerplate code

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Disadvantages of Spring Boot CLI

• Not commonly used in large enterprise projects
• Groovy knowledge may be required
• Less flexible than full Maven/Gradle projects
• Limited use in complex production systems
• Debugging can become difficult for large applications

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Spring Boot CLI vs Spring Initializr

Feature	Spring Boot CLI	Spring Initializr
Purpose	Run applications quickly	Generate starter projects
Configuration	Minimal	Project-based
Language	Groovy	Java/Kotlin/Groovy
Use Case	Rapid prototyping	Production project setup

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Spring Boot CLI vs Traditional Spring Setup

Feature	Spring Boot CLI	Traditional Spring
Configuration Complexity	Low	High
Development Speed	Fast	Slow
Dependency Management	Automatic	Manual
Server Setup	Embedded	External server needed

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Common Interview Questions on Spring Boot CLI

What is Spring Boot CLI?

Spring Boot CLI is a command-line tool used to quickly create and run Spring Boot applications with minimal configuration.

What language does Spring Boot CLI use?

Spring Boot CLI mainly uses Groovy scripts.

What is the advantage of Spring Boot CLI?

It simplifies development by automatically handling dependencies and configurations.

Is Spring Boot CLI used in production?

It is mainly used for rapid prototyping, learning, and quick development rather than large enterprise production systems.

Can Spring Boot CLI generate projects?

Yes. The spring init command can generate Spring Boot starter projects.

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Best Practices for Using Spring Boot CLI

• Use it for rapid prototyping and learning
• Keep scripts simple and modular
• Use proper dependency versions with @Grab
• Move to Maven or Gradle for large enterprise projects
• Avoid complex business logic in single Groovy files

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Real-World Usage of Spring Boot CLI

Spring Boot CLI is commonly used for:

• Learning Spring Boot
• Creating proof-of-concept applications
• Rapid API prototyping
• Testing Spring features quickly
• Demo applications
• Interview preparation

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Conclusion

Spring Boot CLI is a lightweight and powerful command-line tool that simplifies Spring Boot application development.

It allows developers to quickly create and run applications using Groovy scripts with minimal setup and automatic configuration.

Although it is not commonly used for large-scale enterprise applications, it is extremely useful for learning, rapid prototyping, demos, and testing Spring Boot features quickly.

Understanding Spring Boot CLI helps developers better understand the Spring Boot ecosystem, auto-configuration, and dependency management concepts.