步骤

1. 打开IntelliJ IDEA，选择 Create New Project
2. 选择 Spring Initializr
3. 在弹出的窗口中，选择项目名称、项目路径、项目类型、语言和Spring Boot版本等
4. 点击 Next
5. 填写 Group、Artifact、Name、Description、Package等信息
6. 点击 Next
7. 选择 Spring Boot Starter 依赖，如 Web、JPA、MySQL等
8. 点击 Next
9. 配置项目信息，如项目名称、项目路径等
10. 点击 Finish

目录结构

├── src
│   ├── main
│   │   ├── java
│   │   │   └── com.example.demo
│   │   │       ├── controller
│   │   │       │   └── UserController.java
│   │   │       ├── dao
│   │   │       │   └── UserRepository.java
│   │   │       ├── entity
│   │   │       │   └── User.java
│   │   │       ├── service
│   │   │       │   ├── impl
│   │   │       │   │   └── UserServiceImpl.java
│   │   │       │   └── UserService.java
│   │   │       └── DemoApplication.java
│   │   └── resources
│   │       ├── application.yml
│   │       ├── static
│   │       └── templates
│   └── test
│       └── java
│           └── com.example.demo
│               └── DemoApplicationTests.java
└── pom.xml

配置内容

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>demo</artifactId>  
    <version>0.0.1-SNAPSHOT</version>  
    <packaging>jar</packaging>  
    <name>demo</name>  
    <description>Demo project for Spring Boot</description>  
    <parent>  
        <groupId>org.springframework.boot</groupId>  
        <artifactId>spring-boot-starter-parent</artifactId>  
        <version>2.5.3</version>  
        <relativePath/>  
    </parent>  
    <properties>  
        <java.version>1.8</java.version>  
    </properties>  
    <dependencies>  
        <dependency>  
            <groupId>org.springframework.boot</groupId>  
            <artifactId>spring-boot-starter-data-jpa</artifactId>  
        </dependency>  
        <dependency>  
            <groupId>org.springframework.boot</groupId>  
            <artifactId>spring-boot-starter-web</artifactId>  
        </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>  

application.yml

server:  
  port: 8080  
spring:  
  datasource:  
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8  
    username: root  
    password: 123456  
    driver-class-name: com.mysql.jdbc.Driver  
  jpa:  
    hibernate:  
      ddl-auto: update  
    show-sql: true  
    database: mysql  
    database-platform: org.hibernate.dialect.MySQL5Dialect  

数据库选择MySQL5.7，使用JPA框架

实体类

@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private Integer age;

    public User() {
    }

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    // getter and setter ...
}

DAO层

UserRepository.java

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

user.sql

CREATE TABLE `user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4;

服务层

UserService.java

public interface UserService {
    List<User> findAll();
    User findById(Long id);
    User save(User user);
    User update(User user);
    void deleteById(Long id);
}

UserServiceImpl.java

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserRepository userRepository;

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

    @Override
    public User findById(Long id) {
        return userRepository.findById(id).orElse(null);
    }

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

    @Override
    public User update(User user) {
        if (user.getId() == null) {
            return null;
        }
        return userRepository.save(user);
    }

    @Override
    public void deleteById(Long id) {
        userRepository.deleteById(id);
    }
}

控制层

UserController.java

@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/users")
    public List<User> findAll() {
        return userService.findAll();
    }

    @GetMapping("/users/{id}")
    public User findById(@PathVariable Long id) {
        return userService.findById(id);
    }

    @PostMapping("/users")
    public User save(@RequestBody User user) {
        return userService.save(user);
    }

    @PutMapping("/users")
    public User update(@RequestBody User user) {
        return userService.update(user);
    }

    @DeleteMapping("/users/{id}")
    public void deleteById(@PathVariable Long id) {
        userService.deleteById(id);
    }
}