This comprehensive guide will take you through creating a simple Spring Boot application from scratch, and demonstrate how to build a RESTful API that retrieves data from a database. We will cover the basic concepts and features of Spring Boot, including its benefits and use cases, and the common pitfalls and challenges of working with it. Our step-by-step tutorial will show you how to create the project structure, add dependencies, define entity and repository classes, create a service and controller class, and test the API using Postman. Finally, we will briefly touch on deployment and monitoring with Spring Boot Actuator. If you want to get started with Spring Boot and build robust applications, this tutorial is perfect for you.

System Requirements

Before we get started with Spring Boot, let's ensure that our system meets the following requirements:

• Java 8 or above

• Maven or Gradle installed

• An Integrated Development Environment (IDE)

• Postman

Introduction

Spring Boot is a popular framework for building web applications and microservices using the Spring Framework. Here are the basic concepts and features of Spring Boot, its benefits and use cases, and the common pitfalls and challenges of working with it:

Basic Concepts and Features

• Spring Boot is built on top of the Spring Framework and provides a set of opinionated defaults and auto-configurations to reduce the boilerplate code required to build a Spring application.

• It includes a range of starter dependencies for popular libraries and frameworks, such as Spring Data, Spring Security, and Thymeleaf, which can be easily added to a project.

• Spring Boot also includes an embedded web server, which makes it easy to create standalone web applications that can be deployed without the need for an external web server.

• It supports a wide range of databases and data sources, and provides several ways to configure them, such as application.properties, YAML files, and environment variables.

Benefits and Use Cases

• Spring Boot makes it easy to get started with Spring and build applications quickly.

• It reduces the amount of boilerplate code and configuration required to build a Spring application, which improves developer productivity.

• Its opinionated defaults and auto-configurations help ensure that applications are consistent and follow best practices.

• Spring Boot is suitable for building a wide range of web applications and microservices, including RESTful APIs, web applications, and backend services.

• It is also well-suited for building cloud-native applications, as it provides support for deploying applications to cloud platforms, such as Kubernetes and Cloud Foundry.

Common Pitfalls and Challenges

• While Spring Boot reduces the amount of configuration required, it can still be challenging to configure some aspects of the application, such as security and data sources.

• As Spring Boot includes a lot of dependencies, it can lead to large application sizes and longer startup times.

• Developers need to be careful not to rely too heavily on the auto-configurations and to ensure that they understand how the application is configured and what dependencies are included.

• Spring Boot is constantly evolving, which means that developers need to keep up-to-date with the latest changes and best practices.

Overall, Spring Boot is a powerful and popular framework for building web applications and microservices. By understanding its basic concepts and features, benefits and use cases, and common pitfalls and challenges, developers can build robust and scalable applications that take advantage of its many features and capabilities.

Step 1: Create a Spring Boot Project

The first step is to create a new Spring Boot project using the Spring Initializr. You can do this by visiting start.spring.io and selecting the following options:

• Project: Maven

• Language: Java

• Spring Boot: 2.5.x or higher

• Group: online.techstories.demo

• Artifact: getting-started

• Packaging: jar

• Java Version: 8

• Dependencies: Spring Web, Spring Data JPA, Spring Boot Actuator, H2 Database

Click "Generate" to download the project.

The Main class should look like below:

@SpringBootApplication
public class GettingStartedApplication {

    public static void main(String[] args) {
        SpringApplication.run(GettingStartedApplication.class, args);
    }

}

This class is annotated with @SpringBootApplication, which is a convenience annotation that combines @Configuration, @EnableAutoConfiguration, and @ComponentScan. These three annotations are used to configure the application context, enable auto-configuration, and scan for components respectively. The main method simply starts the application by calling SpringApplication.run().

Step 2: Create an Entity class

An Entity class represents a table in a database. To create an Entity class, we need to define a class with the @Entity annotation. Follow the below steps to create an Entity class:

1. Create a new package called online.techstories.demo.gettingstarted.model

2. Create a new class called Employee in the above package.

3. Add the @Entity annotation to the Employee class.

4. Add the @Id annotation to the id field.

5. Add the @GeneratedValue annotation to the id field.

Here is an example of an Employee Entity class:

@Entity
public class Employee {

    @Id
    @GeneratedValue
    private Long id;
    private String name;
    private String email;

    // Constructor, getters, and setters
}

Step 3: Define a Repository class

A Repository class is responsible for interacting with the database. To create a Repository class, we need to define an interface that extends the JpaRepository interface. Follow the below steps to create a Repository class:

1. Create a new package called online.techstories.demo.gettingstarted.repository

2. Create a new interface called EmployeeRepository in the above package.

3. Extend the JpaRepository interface and specify the Entity class and primary key type.

4. Add the @Repository annotation to the Employee class.

Here is an example of an EmployeeRepository interface:

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long> {
}

Step 4: Create a Service class

A Service class contains the business logic of the application. To create a Service class, we need to define a class with the @Service annotation. Follow the below steps to create a Service class:

1. Create a new package called online.techstories.demo.gettingstarted.service

2. Create a new class called EmployeeService in the above package.

3. Add the @Service annotation to the EmployeeService class.

4. Inject the EmployeeRepository in the EmployeeService class.

5. Define a method to get all employees from the database.

Here is an example of an EmployeeService class:

@Service
public class EmployeeService {

    @Autowired
    private EmployeeRepository employeeRepository;

    public List<Employee> getAllEmployees() {
        return employeeRepository.findAll();
    }
}

Step 5: Create a Controller class

A Controller class is responsible for handling HTTP requests and returning the appropriate response. To create a Controller class, we need to define a class with the @RestController annotation. Follow the below steps to create a Controller class:

1. Create a new package called online.techstories.demo.gettingstarted.controller

2. Create a new class called EmployeeController in the above package.

3. Add the @RestController annotation to the EmployeeController class.

4. Inject the EmployeeService in the EmployeeController class.

5. Define a method to get all employees and return them as a JSON array.

Here is an example of an EmployeeController class:

@RestController
public class EmployeeController {

    @Autowired
    private EmployeeService employeeService;

    @GetMapping("/employees")
    public List<Employee> getAllEmployees() {
        return employeeService.getAllEmployees();
    }
}

Step 6: Deploy the application

To deploy a Spring Boot application, you can create a deployable package in the form of a JAR or a WAR file. You can then deploy this package to a server that supports Java web applications.

To create a JAR file using Maven, run the following command:

mvn package

This command creates a JAR file in the target directory of your project.

If you're using Gradle, you can run the following command to create a JAR file:

./gradlew bootJar

This command creates a JAR file in the build/libs directory of your project.

Step 7: Run the Application

Now that we've written our code, it's time to run the application. To run the application using Maven, navigate to the root directory of your project in the terminal and run the following command:

mvn spring-boot:run

This command starts the Spring Boot application and deploys it to an embedded server.

If you're using Gradle, you can run the following command:

./gradlew bootRun

Step 8: Using Spring Boot Actuator

Spring Boot Actuator provides a set of endpoints and tools for monitoring and managing your Spring Boot application. It includes endpoints for checking the health of the application, inspecting metrics, and viewing the application's configuration.

To enable Spring Boot Actuator, add the following dependency to your pom.xml file:

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

If you're using Gradle, you can add the following line to your build.gradle file:

implementation 'org.springframework.boot:spring-boot-starter-actuator'

Once you've added the dependency, you can access the Actuator endpoints by navigating to http://localhost:8080/actuator in your web browser. This will display a list of available endpoints and their current status.

Step 9: Test the API using Postman

Postman is a tool that allows us to test APIs by sending HTTP requests and receiving responses. Follow the below steps to test the API:

1. Open Postman and create a new request.

2. Set the request method to GET.

3. Set the request URL to http://localhost:8080/employees

4. Send the request and verify that the response contains a JSON array of employees.

Congratulations! You have successfully created a simple Spring Boot application that retrieves data from a database and exposes it as a RESTful API.

Conclusion

In this tutorial, we covered the basic concepts and features of Spring Boot, its benefits and use cases, and the common pitfalls and challenges of working with it. We also provided a step-by-step guide on how to create a simple Spring Boot application that retrieves data from a database and exposes it as a RESTful API. We hope this tutorial was helpful, and you can now get started with Spring Boot and build amazing applications!

GitHub Code

Please refer to the below GitHub location for the completed project:

https://github.com/BeingSujeetK/techstories-demo-spring-boot/tree/main/springboot-getting-started