Spring Boot Backend Development Course, Libraries and Frameworks

Spring Boot is a Java-based framework that helps developers easily create web applications and microservices. In this course, we will explore the core elements of Spring Boot and carry out actual projects using various libraries and frameworks.

1. Overview of Spring Boot

Spring Boot is a conceptual extension of the Spring framework, designed to minimize application configuration and provide various configuration options to start projects easily. The main features of Spring Boot are:

  • Auto Configuration: Spring Boot automatically configures settings that are generally required.
  • Embedded Server: Servers like Tomcat and Jetty are embedded, so no separate server environment setup is necessary.
  • Starter Packages: Provides bundled libraries needed for specific functionalities, making integration easy.

2. Spring Boot Architecture

Spring Boot consists of various components and is designed following the MVC (Model-View-Controller) pattern. The main architectural components are:

  • Controller: Handles HTTP requests and calls related services to return results.
  • Service: Implements business logic and handles interactions with the database.
  • Repository: Responsible for CRUD operations with the database.

3. Installing and Setting Up Spring Boot

To use Spring Boot, you need to install JDK and either Maven or Gradle. Follow the steps below to install:

  1. Install JDK: Install Oracle JDK or OpenJDK.
  2. Install Maven/Gradle: Choose Maven or Gradle for managing Spring Boot projects and proceed with installation.

4. Creating a Spring Boot Project

You can create a new project through the Spring Initializer website (start.spring.io). Select the necessary dependencies and enter project metadata to download it.

4.1 Setting Up a Gradle-Based Project

plugins {
    id 'org.springframework.boot' version '2.5.6'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

5. Key Libraries of Spring Boot

Spring Boot provides several libraries as defaults. The most commonly used libraries are:

5.1 Spring Web

An essential component for creating RESTful web services or developing web applications based on the MVC architecture.

5.2 Spring Data JPA

A library that simplifies interactions with the database using JPA (Java Persistence API), enabling object-oriented management of the database.

5.3 Spring Security

A library used to add security to applications, helping to easily implement authentication and authorization.

5.4 Spring Boot Actuator

A library that provides application status and management information, facilitating application monitoring and management in production environments.

6. Developing RESTful APIs

Let’s learn how to develop RESTful APIs using Spring Boot. REST APIs offer methodologies to design interactions between clients and servers.

6.1 Adding Dependencies

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
}

6.2 Creating a Controller

Below is an example of a simple REST API controller:

import org.springframework.web.bind.annotation.*;

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

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

6.3 Method Description

In the code above, @RestController indicates that this class is a REST API controller, while @GetMapping defines a method that handles HTTP GET requests. @RequestMapping sets the base URL path.

7. Integrating with a Database

This section introduces how to integrate Spring Boot with a database. Commonly used databases include MySQL and PostgreSQL, and database interactions are managed through JPA.

7.1 Database Configuration

Set the database connection information in the application.properties file:

spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=update

7.2 Creating an Entity

Create an entity class that maps to a database table. Below is an example of a simple user entity:

import javax.persistence.*;

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String name;
    
    private String email;

    // Getters and Setters
}

7.3 Creating a Repository Interface

Create a repository interface for interacting with the database:

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
}

8. Implementing the Service Layer

Implement a service layer that handles business logic to increase code reusability and meet business requirements.

8.1 Creating a Service Class

The service class can be implemented as follows:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public List<User> getAllUsers() {
        return userRepository.findAll();
    }
}

9. Applying Spring Security

To add security to the application, configure Spring Security. This allows you to implement user authentication and authorization features.

9.1 Adding Dependencies

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-security'
}

9.2 Configuring Security

Create a SecurityConfig class to configure Spring Security:

import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
            .anyRequest().authenticated()
            .and()
            .httpBasic();
    }
}

10. Testing and Deployment

Once all functionalities are implemented, write unit tests and integration tests to verify that they work correctly. Then, you can deploy the application using Docker and Kubernetes.

10.1 Unit Testing

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class MyApplicationTests {

    @Test
    void contextLoads() {
    }
}

11. Conclusion

Spring Boot is a very useful framework for modern web application development. We hope this course has laid the foundation for you to develop robust and maintainable web applications using the various features and libraries of Spring Boot.

12. References