Step-by-Step Guide to Setting Up a Spring Boot Project

 Spring Boot is a powerful framework for building Java-based backend applications. It simplifies the setup process and allows developers to create stand-alone, production-ready applications with minimal configuration.

In this guide, we will walk through the Spring Boot setup process, covering everything from installation to running your first Spring Boot application. By the end, you'll have a fully functional Java backend project.

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Prerequisites

Before setting up a Spring Boot project, ensure you have the following installed:

• Java Development Kit (JDK 17 or later)
• Maven or Gradle (for dependency management)
• IDE (IntelliJ IDEA, Eclipse, or VS Code)
• Spring Boot CLI (optional)

Checking Java Installation

To verify if Java is installed, open a terminal or command prompt and run:

java -version

If Java is not installed, download and install it from the Oracle JDK or OpenJDK.

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Step 1: Creating a Spring Boot Project

There are multiple ways to create a Spring Boot project:

1.1 Using Spring Initializr (Recommended)

Spring Initializr is an online tool for generating Spring Boot projects.

1. Go to Spring Initializr
2. Select the following options:
• Project: Maven / Gradle
• Language: Java
• Spring Boot Version: Latest Stable Version
• Dependencies: Spring Web, Spring Boot DevTools, Lombok (optional), and H2 Database (optional)
3. Click Generate to download the project as a ZIP file.
4. Extract the ZIP and open it in your IDE.

1.2 Using Spring Boot CLI

If you have Spring Boot CLI installed, run the following command:

spring init --name=my-spring-boot-app --dependencies=web my-spring-boot-app

This will generate a new Spring Boot project with Spring Web dependency.

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Step 2: Understanding the Project Structure

Once you open the project in an IDE, you will see the following structure:

my-spring-boot-app/
├── src/
│   ├── main/
│   │   ├── java/com/example/demo/
│   │   │   ├── DemoApplication.java (Main Class)
│   │   ├── resources/
│   │   │   ├── application.properties (Configuration File)
│   ├── test/ (Test cases)
├── pom.xml (Maven Build File)

Key Files:

• DemoApplication.java: The main entry point of the Spring Boot application.
• application.properties: Configuration file for the application.
• pom.xml or build.gradle: Manages project dependencies.

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Step 3: Running the Spring Boot Application

To run the project, navigate to the root folder and use one of the following methods:

Using Maven:

mvn spring-boot:run

Using Gradle:

gradle bootRun

Running as a Java Application

You can also run the project directly from the main class:

java -jar target/my-spring-boot-app-0.0.1-SNAPSHOT.jar

Once started, the application will be available at:

http://localhost:8080

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Step 4: Creating a Simple REST API

Now, let's create a simple REST Controller in Spring Boot.

Creating a Controller Class

Inside the com.example.demo package, create a new class HelloController.java:

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api")
public class HelloController {

    @GetMapping("/hello")
    public String sayHello() {
        return "Hello, Spring Boot!";
    }
}

Testing the API

Run the Spring Boot application and open a browser or use Postman to access:

http://localhost:8080/api/hello

Expected Output:

Hello, Spring Boot!

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Step 5: Configuring Application Properties

Spring Boot uses the application.properties or application.yml file for configuration.

Example application.properties:

server.port=9090
spring.application.name=MySpringBootApp

Restart the application, and now it will run on port 9090 instead of the default 8080.

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Step 6: Connecting to a Database

Spring Boot supports multiple databases, including MySQL, PostgreSQL, and H2. Let's configure an H2 in-memory database for this project.

Adding Database Dependencies (For Maven)

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

Updating application.properties:

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.h2.console.enabled=true

Now, access the H2 database console at:

http://localhost:9090/h2-console

Use JDBC URL: jdbc:h2:mem:testdb

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Common Errors & Troubleshooting

1. Port Already in Use

Error:

Port 8080 is already in use

Solution: Change the port in application.properties:

server.port=9090

2. ClassNotFoundException: org.h2.Driver

Solution: Ensure that the H2 dependency is included in pom.xml.

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Spring Boot Interview Questions

1. What is Spring Boot and how is it different from Spring Framework?
2. How does Spring Boot handle dependency management?
3. What are the key features of Spring Boot?
4. How do you create a Spring Boot project using Spring Initializr?
5. What is the purpose of application.properties in Spring Boot?
6. How do you change the default port in Spring Boot?
7. What are Spring Boot starters?
8. What is the difference between @Component, @Service, and @Repository annotations?
9. How do you handle exceptions in Spring Boot?
10. How do you secure a Spring Boot application?

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Conclusion

Setting up a Spring Boot project is quick and efficient with tools like Spring Initializr and Spring Boot CLI. With minimal configuration, you can develop Java backend applications efficiently. By following this Spring Boot tutorial, you've created a REST API and configured a database, giving you a solid foundation to build upon.

Got questions? Leave a comment below! 🚀