What is Spring Boot CLI and how to execute the Spring Boot project using boot CLI?

Question

Accepted Answer

Spring Boot CLI (Command Line Interface) is a lightweight tool that allows developers to create, run, and test Spring Boot applications directly from the command line without setting up a complete Maven or Gradle project. It uses Groovy scripts and automatically manages dependencies through Spring Boot's auto-configuration mechanism.

Key Points:
• Spring Boot CLI reduces boilerplate code and simplifies rapid prototyping.
• It automatically downloads and manages required dependencies.
• It is mainly used for learning, demonstrations, proof-of-concepts, and small applications.

Example:
Suppose you want to quickly create and run a REST API without creating a full Maven project structure. Using Spring Boot CLI, you can write a simple Groovy script and execute it immediately from the terminal.

Code Example:

```
@RestController
class HelloController {

@RequestMapping("/")
    String home() {
```
        return "Hello Spring Boot CLI"
```
    }
}
```
Execution Command:

spring run app.groovy

This command automatically starts the embedded server and runs the application.

Steps to Execute a Spring Boot Application Using CLI:

1. Install Spring Boot CLI

Verify installation:

spring --version

2. Create a Groovy Script

Example:

app.groovy

3. Navigate to the Project Directory

cd project-directory

4. Execute the Application

spring run app.groovy

5. Access the Application

http://localhost:8080

Useful Spring Boot CLI Commands:

Run Application:

spring run app.groovy

Test Application:

spring test app.groovy

Package Application:

spring jar myapp.jar app.groovy

Initialize Project:

spring init --dependencies=web,data-jpa demo-project

Advantages:
• Faster application setup.
• Minimal configuration required.
• Automatic dependency management.
• Ideal for rapid development and experimentation.

Limitations:
• Uses Groovy instead of standard Java source files.
• Not commonly used in enterprise production projects.
• Limited flexibility compared to Maven or Gradle projects.

Real-World Usage:
Spring Boot CLI is often used for:

• Learning Spring Boot concepts.
• Creating quick prototypes.
• Building demonstration applications.
• Testing framework features.

Most enterprise applications prefer Maven or Gradle for dependency management and build automation.

Interview Tip:
A concise interview answer is: Spring Boot CLI is a command-line tool that allows developers to create and run Spring Boot applications using Groovy scripts without creating a full Maven or Gradle project. After installing the CLI, an application can be executed using the command `spring run app.groovy`, which automatically resolves dependencies and starts the embedded server.