SpringBoot利用jpa连接MySQL数据库的方法

<!--添加Jpa依赖-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <!--数据库链接驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

# 应用服务 WEB 访问端口
server:
  port: 8080
# 应用名称
spring:
  application:
    name: HelloSpringBoot
  #数据库配置连接
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/hello_jpa?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: "123456"
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    show-sql: true

CREATE TABLE `jpa_user`  (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '自增主键',
  `username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '用户名称',
  `age` tinyint(4) NULL DEFAULT NULL COMMENT '年龄',
  `gender` tinyint(4) NULL DEFAULT NULL COMMENT '性别0女 1男',
  `phone` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '手机号',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

//引入lombok的getset注解，也可以不引入，自己写下面字段的对应getset方法
@Getter
@Setter
//注解此类为实体类
@Entity
//关联数据库表的名称
@Table(name = "jpa_user")
public class User {
 
    //声明属性为主键
    @Id
    //指定主键生成策略
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    // @Column注解，设置属性关联的数据库表字段
    // 注意：如果属性名和表字段名相同，可以不设置，比如这个实体类对应的所有字段就都是与数据库表字段相同的，都可以不设置Column注解
    @Column(name = "id")
    private Long id;
 
    @Column(name = "username")
    private String username;
 
    @Column(name = "age")
    private Integer age;
 
    @Column(name = "gender")
    private Integer gender;
 
    @Column(name = "phone")
    private String phone;
 
    //驼峰命名法和数据库中的下划线字段是对应的
    @Column(name = "access_card_number")
    private String accessCardNumber;
 
}

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

        //insert into jpa_user (access_card_number, age, gender, phone, username) values (?, ?, ?, ?, ?)
        User user = new User();
        user.setUsername("test");
        user.setPhone("13112345678");
        user.setAge(18);
        user.setGender(0);
        user.setAccessCardNumber("ic_001");
        userRepository.save(user);

//select * from jpa_user user where user.id=?
        User user = userRepository.findById(id).orElse(null);

//update jpa_user set access_card_number=?, age=?, gender=?, phone=?, username=? where id=?
        User user = userRepository.findById(1L).orElse(null);
        user.setPhone("13212345678");
        userRepository.save(user);

//update jpa_user set access_card_number=?, age=?, gender=?, phone=?, username=? where id=?
        User user = userRepository.findById(1L).orElse(null);
        user.setPhone("13212345678");
        userRepository.save(user);

//select * from jpa_user user where (user.age between ? and ?) and user.gender=?
 
List<User> findByAgeBetweenAndGender(int minAge, int maxAge, int gender);