Spring Boot backend development 보관 - Page 22 of 32

Spring Boot Backend Development Course, Understanding the Project with Illustrations

Hello! In this course, we will cover the basics to advanced topics of backend development using Spring Boot. This course is designed to be visually easy to understand with illustrations, making it accessible for beginners. This step-by-step project covers all the elements needed to develop a real web application.

1. What is Spring Boot?

Spring Boot is a modern lightweight framework based on the Spring Framework. It minimizes the time developers spend on setup and configuration tasks, fundamentally simplifying the bootstrap process of Spring applications.

Spring Boot Architecture

Figure 1: Spring Boot Architecture

The main advantages of Spring Boot are as follows:

Fast development: Provides an embedded Tomcat server and automatic configuration features.
Easy deployment: Can be easily deployed on various platforms.
Productive development: Powerful features can be accessed with simple setup.

2. Setting Up the Development Environment

To develop a Spring Boot application, you need to install JDK, Maven, and an IDE. Here’s how to set up each tool.

2.1 Installing JDK

To use Spring Boot, you need to install the Java Development Kit (JDK). Download and install the latest version of the JDK. After installation, set the JAVA_HOME environment variable.

2.2 Installing Maven

Maven is a tool for dependency management. After installing Maven, add the Maven bin path to the PATH environment variable.

2.3 Installing an IDE

You can conveniently manage Spring Boot projects using IDEs like IntelliJ IDEA or Eclipse. IntelliJ IDEA, in particular, is highly recommended due to its excellent support for integration with Spring Boot.

3. Creating Your First Spring Boot Project

Now let’s create a Spring Boot project. You can use Spring Initializr to generate the project. Follow the steps below:

Access the Spring Initializr website.
Enter the project metadata.
Add dependencies. (Spring Web, Spring Data JPA, H2 Database, etc.)
Download the project and open it in your IDE.

3.1 Understanding the Project Structure

The generated project has the following structure:

my-spring-boot-project/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/
│   │   │       └── example/
│   │   │           └── demo/
│   │   │               ├── DemoApplication.java
│   │   │               └── controller/
│   │   │               └── service/
│   │   │               └── repository/
│   │   └── resources/
│   │       ├── application.properties
│   └── test/
│       └── java/
└── pom.xml

In this structure, DemoApplication.java serves as the entry point of the application.

4. Developing a RESTful API

Now let’s create a basic RESTful API. Spring Boot supports building RESTful services very easily.

4.1 Creating the Model Class

First, let’s create a data model class. For example, we will create a User class to store user information.

package com.example.demo.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String email;

    // getters and setters
}

4.2 Creating the Repository Interface

To query or modify data, let’s create a repository interface using JPA.

package com.example.demo.repository;

import com.example.demo.model.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository {
}

4.3 Creating the Service Class

Let’s create a service class to handle business logic.

package com.example.demo.service;

import com.example.demo.model.User;
import com.example.demo.repository.UserRepository;
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 getAllUsers() {
        return userRepository.findAll();
    }

    public User createUser(User user) {
        return userRepository.save(user);
    }

    // Other methods
}

4.4 Creating the Controller Class

Now let’s create a controller class to handle HTTP requests.

package com.example.demo.controller;

import com.example.demo.model.User;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/users")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping
    public List getAllUsers() {
        return userService.getAllUsers();
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        return userService.createUser(user);
    }
}

5. Database Configuration

Now let’s set up the H2 database. Modify the application.properties file to add the database configuration.

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.h2.console.enabled=true
spring.jpa.hibernate.ddl-auto=update

6. Testing

Now everything is ready. When you run the Spring Boot application, you can create and query user data through the RESTful API using the embedded H2 database. Tools like Postman can be used to perform API testing.

Postman Usage Example

Figure 2: API Testing in Postman

7. Conclusion

In this course, you learned how to create a simple backend application using Spring Boot. Spring Boot helps you progress projects quickly without complex configurations and is very suitable for developing RESTful APIs. I hope this course has laid the foundation for you to delve deeper into backend development with Spring Boot.

8. Additional Resources

If you want to learn more, check out the resources below:

Spring Boot Backend Development Course, Git and GitHub

Hello! In this tutorial, we will explore how to utilize Git and GitHub while starting Spring Boot development. Let’s understand the importance of source code management and version control, and learn how to apply them in actual projects.

1. What is Spring Boot?

Spring Boot is a sub-project of the Spring framework, which is a Java-based web application development framework, and it helps to develop web applications faster and more easily. Its main features include:

Auto-configuration: Spring Boot automatically configures necessary settings without the need for the developer to define a configuration file.
Integration with the Spring ecosystem: Spring Boot can be easily integrated with various Spring projects (Spring MVC, Spring Data, etc.).
Standalone: It can be distributed as a standalone JAR file without requiring a separate web server when deployed on a server.

2. What are Git and GitHub?

2.1 Git

Git is a distributed version control system that records the history of code changes and allows multiple developers to work simultaneously. Git has several advantages, including:

Fast performance: All operations are performed locally, leading to smooth software performance.
Small size: The size of the repository is kept small, allowing effective management of multiple versions of code.
Distributed: Each developer’s local repository is managed independently, so it does not rely on a central server.

2.2 GitHub

GitHub is a platform that helps manage source code using Git, allowing for collaboration and public sharing. Its main features include:

Code hosting: You can store and manage project code in the cloud.
Issue tracking: It provides useful tools for tracking and managing bugs or improvement requests.
Collaboration: It enables multiple developers to work on the same project simultaneously.

3. Setting up the environment

3.1 Installing Java

To use Spring Boot, you need to install the Java Development Kit (JDK). You can install it from Oracle’s official website or OpenJDK.

sudo apt update
sudo apt install openjdk-11-jdk
java -version

3.2 Installing Spring Boot CLI

Using the Spring Boot CLI (Command Line Interface), you can easily create Spring Boot applications. The installation steps are as follows:

brew tap spring-io/tap
brew install springboot

3.3 Installing Git

If Git is not yet installed, you can install it using the following command:

sudo apt install git

3.4 Creating a GitHub account

4. Creating a simple Spring Boot application

Now, let’s create a Spring Boot application. Use the following command to create a new project:

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

Once the project is created, navigate to the directory.

cd my-spring-boot-app

4.1 Creating a simple REST API

Let’s write a simple example that provides data using a REST API in a Spring Boot application. Create a file named `src/main/java/com/example/myapp/MyController.java` and write the following code:

package com.example.myapp;

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

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

Now, let’s run the application. You can execute the following command to run the application:

./mvnw spring-boot:run

After running, check the result by accessing http://localhost:8080/hello in your web browser, where you should see the message “Hello, Spring Boot!”.

5. Version control using Git and GitHub

5.1 Initializing Git

Now, let’s initialize Git in the project. Move to the project folder and enter the following command:

git init

Executing this command will create a .git directory in the current directory, initializing a Git repository.

5.2 Adding files and committing

Let’s add files and commit. Use the following command to add all files to the staging area:

git add .

Then proceed with a commit.

git commit -m "Initial commit: Created Spring Boot application"

5.3 Creating a repository on GitHub

Go to GitHub and create a new repository. After creating the new repository, add the remote repository.

git remote add origin https://github.com/username/my-spring-boot-app.git

5.4 Pushing to the remote repository

Now, let’s push the project to GitHub. Push using the following command:

git push -u origin master

Now you can check the project code on GitHub.

6. Utilizing GitHub for team collaboration

As the project grows, you will collaborate with multiple team members, and you can utilize various collaboration features of GitHub at this time. There are many features, including merge requests (Pull Requests), code reviews, and issue management.

6.1 Issue management

Create issues to manage bugs or requests. Issues allow team members to share opinions and assign tasks.

6.2 Code review

After pushing the code, you can request a review from team members. Reviews help improve code quality and receive various feedback.

6.3 Merge requests (Pull Request)

After developing a new feature, use a pull request to merge that feature into the main branch. This option allows other team members to review and approve the changes.

7. Conclusion

In this tutorial, we created a simple backend application using Spring Boot and explored source code management and collaboration methods using Git and GitHub. Through this process, we hope you gain a basic understanding of Spring Boot and Git.

To further enhance your skills, search for additional resources and apply them to various projects. In the next tutorial, we will delve deeper into Spring Boot’s JSON processing, configuration management, and more.

References

Spring Boot Backend Development Course, Aspect-Oriented Programming

Efficiency in modern software development is achieved through the introduction of various programming paradigms. In particular, Spring Boot is a very popular framework in the Java ecosystem, primarily used for microservice architecture and RESTful API development. This article discusses the concepts and practicality of Aspect-Oriented Programming (AOP) in the backend development process based on Spring Boot.

1. What is Aspect-Oriented Programming (AOP)?

Aspect-Oriented Programming (AOP) is a programming paradigm that allows for the separation and management of cross-cutting concerns without affecting the core business logic of the program. It is used alongside Object-Oriented Programming (OOP) to clearly separate business logic from cross-cutting concerns, thereby improving code readability and maintainability and helping reduce code duplication.

Separation of Concerns: This separates the business logic of the application from common modules (e.g., security, logging, transaction management), making the code base more concise.
Reusability: Common functionalities can be written once and reused in multiple places.
Improved Maintainability: Since common logic is managed centrally, maintaining the code becomes easier when modifications are needed.

2. AOP Support in Spring

The Spring Framework provides several features to support AOP, allowing developers to easily define and apply various aspects. Spring AOP is proxy-based and primarily operates at method execution points.

2.1 Key Terms of AOP

Aspect: An element that modularizes a cross-cutting concern. For example, an aspect responsible for logging.
Join Point: A point where an aspect can be applied, usually at a method call.
Advice: The action to be taken at a join point. This is the core functionality of AOP.
Pointcut: An expression that defines which join points an advice should be applied to.
Weaving: The process of combining aspects with business logic. This can occur at runtime, compile time, or load time.

3. Applying AOP in Spring Boot

Setting up AOP in Spring Boot is relatively straightforward. It consists of the following steps.

3.1 Adding Dependencies

To use AOP in a Spring Boot application, you need to add the `spring-boot-starter-aop` dependency. Add the following code to your `pom.xml` file.

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

3.2 Creating an Aspect Class

Create a class that defines the aspect. This class will use the @Aspect annotation to indicate that it is an aspect. The example below implements an aspect that logs messages before method execution.

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class LoggingAspect {

    @Before("execution(* com.example.service.*.*(..))")
    public void logBeforeMethod() {
        System.out.println("Before method execution: logging");
    }
}

3.3 Defining Pointcut

In the example above, the logBeforeMethod() method defines a pointcut that logs messages right before executing any method in the service package. You can specify the package and return type in the execution expression.

3.4 Testing

You can now log messages from your service methods. When you call a method in the service class, the log message will be printed by the aspect.

import org.springframework.stereotype.Service;

@Service
public class MyService {
    public void performTask() {
        System.out.println("Performing task...");
    }
}

3.5 Caution

When using AOP, performance degradation should be considered. Especially if the pointcut is broad, performance issues may arise, so it’s advisable to specify the necessary scope only.

4. Use Cases of AOP

AOP can be utilized in various fields. Here are some common use cases.

4.1 Logging

Logs can be recorded at the start and end of a method, allowing for tracking the flow of function calls. This is useful for debugging and performance monitoring.

4.2 Transaction Management

AOP can be used to define the transaction boundaries of business logic and commit only when completed successfully. This helps reduce duplicate transaction-related code within your codebase.

4.3 Security

Access control can be implemented for specific methods or classes. AOP can be employed to allow method execution only under certain conditions.

5. Optimizing AOP in Spring Boot

Since AOP operates based on proxies, poorly configured aspects may affect system performance. Here are some tips for optimizing AOP in Spring Boot.

5.1 Pointcut Optimization

Narrow the scope of pointcuts to minimize the targets of AOP application. For example, limiting to specific packages or classes can prevent performance degradation.

5.2 Performance Monitoring

Monitor the performance when using AOP in your application to prevent excessive time consumption. This will help continuously assess the impact of AOP.

5.3 Method Separation

Separate methods to allow common logic to be reused, preventing tight coupling between aspects and business logic. This benefits code reusability and readability.

Conclusion

Aspect-Oriented Programming is one of the important paradigms in backend development using Spring Boot. By effectively separating and managing cross-cutting concerns, developers can focus more on business logic. This approach leads to cleaner code that is easier to maintain and reduces redundancy.

I hope you will experiment and plan for various application areas of AOP in the future. I look forward to seeing you leverage common modules like AOP to contribute to the development of better software in your future development processes.

Spring Boot Backend Development Course, Development Environment, Creating a Project

Hello! In this course, we will learn how to develop backend applications using Spring Boot. Spring Boot is a lightweight framework based on the Spring Framework that helps you quickly develop production-grade applications. In this article, we will explain in detail how to set up the development environment and create a project.

1. Setting Up the Development Environment

Before starting a Spring Boot project, you need to set up the following development environment.

1.1. Install JDK

Since Spring Boot is based on Java, you need to install the JDK (Java Development Kit). The JDK is a tool that compiles and runs Java source code.

JDK Download: [Oracle JDK Download Page](https://www.oracle.com/java/technologies/javase-jdk11-downloads.html) or [OpenJDK Download Page](https://openjdk.java.net/install/)
After installation, check if it was successful by running the command java -version in the terminal.

1.2. Install an IDE

You need to use an IDE (Integrated Development Environment) to write code. There are various IDEs like IntelliJ IDEA, Eclipse, and VSCode, but in this course, we recommend IntelliJ IDEA.

IntelliJ IDEA Download: [JetBrains Official Website](https://www.jetbrains.com/idea/download/)
After installation, you can create a new Spring Boot project through the ‘Create New Project’ menu.

1.3. Install Maven

Spring Boot uses Maven to manage dependencies. You can easily add the necessary libraries by installing Maven.

Maven Download: [Maven Official Website](https://maven.apache.org/download.cgi)
After installation, check if it is completed by running the command mvn -v.

2. Creating a Project

Now that the development environment is fully prepared, the next step is to create a Spring Boot project.

2.1. Using Spring Initializr

Spring Initializr is a web-based tool that allows you to easily create Spring Boot projects. Follow the steps below to create a project.

Open [Spring Initializr](https://start.spring.io/) in your browser.
Select Project: Choose either Maven Project or Gradle Project.
Select Language: Choose Java.
Select Spring Boot Version: Choose the latest stable version (e.g., 2.6.6).
Enter Project Metadata: You need to fill in the following fields.

Group: com.example
Artifact: demo
Name: demo
Description: Demo project for Spring Boot
Package name: com.example.demo
Packaging: Choose Jar.
Java: Select the version that matches your JDK version (e.g., 11).

Add Dependencies: Select the libraries you need for your project. For example, you can add Spring Web, Spring Data JPA, H2 Database, etc.
Click the Generate button to create the project and download the ZIP file.

2.2. Opening the Project in IntelliJ

After extracting the downloaded ZIP file, open IntelliJ IDEA and follow the steps below.

Select ‘File’ -> ‘Open’ and choose the extracted project folder.
IntelliJ will recognize Maven and download the necessary libraries. Once this process is complete, the project structure will be ready.

2.3. Writing Application Code

Now let’s create a simple Spring Boot application. Open the src/main/java/com/example/demo/DemoApplication.java file and enter the following code.

Spring Boot Backend Development Course, Development Environment, Installing IntelliJ on Windows

Hello! In this blog, we will learn about Spring Boot backend development. Backend development is responsible for data processing and business logic in web applications, and various tools and frameworks are needed to perform these functions efficiently. Among them, Spring Boot is a Java-based framework that allows for rapid and convenient development. This article will provide detailed instructions on how to set up the development environment necessary for using Spring Boot, particularly how to install and configure IntelliJ in a Windows environment.

1. What is Spring Boot?

Spring Boot is an extension of the Spring framework designed for rapid application development. It reduces complex XML configurations and provides minimal settings required to run the application. Spring Boot supports embedded servers (e.g., Tomcat, Jetty), making it easy to deploy and run applications.

2. Features of Spring Boot

Auto Configuration: Spring Boot automatically performs basic configuration, helping developers use it easily even if they are not familiar with it.
Standalone Application: Spring Boot applications are packaged with an embedded server and can run independently.
Starter Dependencies: It provides starter packages to quickly add required dependencies.
Actuator: It offers functionality to monitor the state and performance of the application.

3. Setting Up the Development Environment

To use Spring Boot, you will need the Java Development Kit (JDK), an IDE like IntelliJ IDEA, and Spring Initializr. This section will explain how to install and configure IntelliJ on Windows.

3.1 Installing JDK

Download JDK: Download the JDK from Oracle’s official website or OpenJDK.
Installation: Run the downloaded file to install it. After installation, set the environment variable to specify `JAVA_HOME` as the installation directory of the JDK.
Verification: Open a command prompt and enter the command java -version to verify the installation was completed successfully.

3.2 Installing IntelliJ IDEA

IntelliJ IDEA is a Java IDE provided by JetBrains, optimized for Spring Boot development. Let’s follow the steps to install IntelliJ.

Step 1: Download IntelliJ

Visit JetBrains’ official website (https://www.jetbrains.com/idea/download/) and download the free community version.

Step 2: Installation

Run the downloaded installation file.
Follow the installation wizard’s instructions. You can choose useful options like “Create Desktop Shortcut” during the installation options.

Step 3: Initial Setup

Once the installation is complete, launch IntelliJ.
Select “Do not import settings” to use the default configuration.
Choose the theme and other user settings.

Step 4: Installing Plugins

You can install Spring-related plugins from IntelliJ’s plugin marketplace. Go to “File” -> “Settings” -> “Plugins” menu, search for necessary plugins in the “Marketplace” and install them.

4. Creating a Project Using Spring Initializr

After installing IntelliJ, let’s learn how to create a Spring Boot project. Using Spring Initializr allows you to easily create a project template.

Step 1: Create a New Project

Run IntelliJ and select “New Project.”
Select “Spring Initializr” on the left and click “Next.”

Step 2: Enter Project Metadata

Group: com.example
Artifact: demo
Name: demo
Package Name: com.example.demo
Packaging: Selectable (jar or war)
Java Version: Choose the JDK version you will use.

Step 3: Add Dependencies

You can select “Spring Web” for web development and “Spring Data JPA” for database connectivity.
After adding dependencies, click “Next” and then “Finish” to create the project.

5. Basic Structure of a Spring Boot Project

Let’s explain the basic directory structure of the generated project. A Spring Boot project has the following structure:

com
└── example
    └── demo
        ├── DemoApplication.java
        ├── controller
        ├── service
        └── repository

DemoApplication.java: This is the entry point of the Spring Boot application. It performs Spring configuration and component scanning via the @SpringBootApplication annotation.
controller: Contains controller classes responsible for handling web requests.
service: Contains service classes that handle business logic.
repository: Contains repository classes for database access.

6. Creating Your First REST API

Now let’s create a simple REST API that returns user information.

Step 1: Create a Controller

package com.example.demo.controller;

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

@RestController
public class UserController {
    
    @GetMapping("/users")
    public String getUsers() {
        return "User List";
    }
}

Step 2: Run the Application

Run the DemoApplication.java file in IntelliJ to start the application.
Access http://localhost:8080/users in a web browser to verify the result.

7. Conclusion

In this article, we covered how to set up a backend development environment using Spring Boot, how to install IntelliJ, and how to create your first REST API. Spring Boot provides powerful features and flexibility, so I encourage you to continue exploring its various functionalities. The next article will discuss how to integrate a database and create more complex APIs. I hope you learn a lot through consistent practice and hands-on experience.

Thank you!