springBoot整合JPA

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

spring:
  application:
    name: jpa-study
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      # mysql 8.0 以下
      # url: jdbc:mysql://localhost:3306/test?useSSL=false&characterEncoding=utf8&autoReconnect=true
      # driver-class-name: com.mysql.jdbc.Driver
      # mysql 8.0 以上使用
      url: jdbc:mysql://localhost:3306/my-study?useSSL=false&serverTimezone=GMT%2B8&characterEncoding=utf8&autoReconnect=true&failOverReadOnly=false
      driver-class-name: com.mysql.cj.jdbc.Driver
      username: root
      password: 123456
  jpa:
    hibernate:
#      自动更新ddl-auto是hibernate的配置属性，其主要作用是：自动创建、更新、验证数据库表结构。该参数的几种配置如下：
      #    ·create：每次加载hibernate时都会删除上一次的生成的表，然后根据你的model类再重新来生成新表，哪怕两次没有任何改变也要这样执行，这就是导致数据库表数据丢失的一个重要原因。
      #    ·create-drop：每次加载hibernate时根据model类生成表，但是sessionFactory一关闭,表就自动删除。
      #    ·update：最常用的属性，第一次加载hibernate时根据model类会自动建立起表的结构（前提是先建立好数据库），以后加载hibernate时根据model类自动更新表结构，即使表结构改变了但表中的行仍然存在不会删除以前的行。要注意的是当部署到服务器后，表结构是不会被马上建立起来的，是要等应用第一次运行起来后才会。
      #    ·validate：每次加载hibernate时，验证创建数据库表结构，只会和数据库中的表进行比较，不会创建新表，但是会插入新值。
      ddl-auto: update
#      开启驼峰_转换
      naming:
        physical-strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
#        日志中显示sql语
    show-sql: true

@Entity
@Data
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name", length = 20)
    private String name;

    @Column(name = "age", length = 4)
    private int age;
}

@Repository
public interface PersonRepository extends JpaRepository<Person, Long> {
    
}

@RestController
public class PersonController {

    @Autowired
    private PersonRepository personRepository;

    @PostMapping(path = "addPerson")
    public void addPerson(Person person) {
        personRepository.save(person);
    }

    @DeleteMapping(path = "deletePerson")
    public void deletePerson(Long id) {
        personRepository.deleteById(id);
    }

    @GetMapping("getPerson")
    public Object getPerson(){
        Optional<Person> byId = personRepository.findById(1L);
        return personRepository.findById(1L);
    }
    
}

public interface UserRepository extends JpaRepository<User, Long> {

  @Query("select u from User u where u.emailAddress = ?1")
  User findByEmailAddress(String emailAddress);
}

public interface UserRepository extends JpaRepository<User, Long> {

  @Query("select u from User u where u.firstname like %?1")
  List<User> findByFirstnameEndsWith(String firstname);
}

public interface UserRepository extends JpaRepository<User, Long> {

  @Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?1", nativeQuery = true)
  User findByEmailAddress(String emailAddress);
}

public interface UserRepository extends JpaRepository<User, Long> {

  @Query(value = "SELECT * FROM USERS WHERE LASTNAME = ?1",
    countQuery = "SELECT count(*) FROM USERS WHERE LASTNAME = ?1",
    nativeQuery = true)
  Page<User> findByLastname(String lastname, Pageable pageable);
}