Spring Boot Project Structure Example

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my-spring-boot-app
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com
│   │   │       └── example
│   │   │           ├── MySpringBootApplication.java
│   │   │           ├── controller
│   │   │           │   └── UserController.java
│   │   │           ├── service
│   │   │           │   └── UserService.java
│   │   │           ├── dto
│   │   │           │   └── UserDTO.java
│   │   │           ├── dao
│   │   │           │   └── UserDAO.java
│   │   │           └── model
│   │   │               └── User.java
│   │   └── resources
│   │       └── application.properties
│   └── test
│       └── java
│           └── com
│               └── example
│                   └── MySpringBootApplicationTests.java
└── pom.xml
    

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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>my-spring-boot-app</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>my-spring-boot-app</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <java.version>11</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>
    

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package com.example.controller;

import com.example.dto.UserDTO;
import com.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/users")
public class UserController {

    @Autowired
    private UserService userService;

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

    @GetMapping("/{id}")
    public UserDTO getUserById(@PathVariable Long id) {
        return userService.getUserById(id);
    }

    @PostMapping
    public UserDTO createUser(@RequestBody UserDTO userDTO) {
        return userService.createUser(userDTO);
    }

    @PutMapping("/{id}")
    public UserDTO updateUser(@PathVariable Long id, @RequestBody UserDTO userDTO) {
        return userService.updateUser(id, userDTO);
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        userService.deleteUser(id);
        return ResponseEntity.noContent().build();
    }
}
    

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package com.example.service;

import com.example.dto.UserDTO;
import com.example.dao.UserDAO;
import com.example.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.stream.Collectors;

@Service
public class UserService {

    @Autowired
    private UserDAO userDAO;

    public List<UserDTO> getAllUsers() {
        return userDAO.findAll().stream().map(UserDTO::new).collect(Collectors.toList());
    }

    public UserDTO getUserById(Long id) {
        return userDAO.findById(id).map(UserDTO::new).orElse(null);
    }

    public UserDTO createUser(UserDTO userDTO) {
        User user = new User(userDTO);
        user = userDAO.save(user);
        return new UserDTO(user);
    }

    public UserDTO updateUser(Long id, UserDTO userDTO) {
        User user = userDAO.findById(id).orElse(null);
        if (user != null) {
            user.setName(userDTO.getName());
            user.setEmail(userDTO.getEmail());
            user = userDAO.save(user);
            return new UserDTO(user);
        }
        return null;
    }

    public void deleteUser(Long id) {
        userDAO.deleteById(id);
    }
}
    

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package com.example.dto;

import com.example.model.User;

public class UserDTO {

    private Long id;
    private String name;
    private String email;

    public UserDTO() {}

    public UserDTO(User user) {
        this.id = user.getId();
        this.name = user.getName();
        this.email = user.getEmail();
    }

    // Getters and Setters
}
    

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package com.example.dao;

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

@Repository
public interface UserDAO extends JpaRepository<User, Long> {
}
    

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package com.example.model;

import com.example.dto.UserDTO;

import javax.persistence.*;

@Entity
@Table(name = "users")
public class User {

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

    @Column(nullable = false)
    private String name;

    @Column(nullable = false, unique = true)
    private String email;

    public User() {}

    public User(UserDTO userDTO) {
        this.name = userDTO.getName();
        this.email = userDTO.getEmail();
    }

    // Getters and Setters
}
    

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package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MySpringBootApplication {

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