springboot+mysql语句

以下是使用SpringBoot和Spring Data JPA连接MySQL数据库并执行增删改查操作的示例代码：

1.在pom.xml文件中添加MySQL和Spring Data JPA依赖：

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

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

2.在application.properties文件中配置MySQL数据库连接信息：

spring.datasource.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update

3.创建实体类User.java：

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

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

    @Column(nullable = false)
    private String password;

    // 省略getter和setter方法
}

4.创建Repository接口UserRepository.java：

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    User findByUsername(String username);
}

5.创建Controller类UserController.java：

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserRepository userRepository;

    @PostMapping("/add")
    public User addUser(@RequestBody User user) {
        return userRepository.save(user);
    }
    @GetMapping("/get/{id}")
    public User getUser(@PathVariable Long id) {
        return userRepository.findById(id).orElse(null);
    }

    @PutMapping("/update")
    public User updateUser(@RequestBody User user) {
        return userRepository.save(user);
    }

    @DeleteMapping("/delete/{id}")
    public void deleteUser(@PathVariable Long id) {
        userRepository.deleteById(id);
    }
}

6.使用Postman等工具测试接口，例如添加用户：

请求方式：POST

请求URL：http://localhost:8080/user/add

请求参数：

{
    "username": "test",    "password": "123456"
}

返回结果：

{
    "id": 1,
    "username": "test",
    "password": "123456"
}