Spring Data JPA的简单使用

阿里云国际版折扣https://www.yundadi.com

阿里云国际，腾讯云国际，低至75折。AWS 93折免费开户实名账号代冲值优惠多多微信号：monov8 飞机：@monov6

Spring Data JPA的简单使用

1、新建Spring Boot项目，引入对应的依赖
2、根据数据库信息，添加yaml配置信息
3、编写实体类，同时设置好数据库表对应的字段名字
4、编写mapper
5、编写测试类

Spring Data JPA官方地址

1、新建Spring Boot项目，引入对应的依赖

<dependencies>
   <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
        <version>2.7.4</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.16</version>
    </dependency>
   <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <version>2.7.4</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.20</version>
    </dependency>
</dependencies>

2、根据数据库信息，添加yaml配置信息

spring:
  datasource:
    username: root
    password: 123456
    url: jdbc:mysql://localhost:3306/jpa?useSSL=false&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8
    driver-class-name: com.mysql.jdbc.Driver

  jpa:
    show-sql: true
    hibernate:
      ddl-auto: updatez

3、编写实体类，同时设置好数据库表对应的字段名字

@Table
@Entity(name = "user")
@Data
@AllArgsConstructor
@NoArgsConstructor
@EqualsAndHashCode
@ToString
public class User {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "user_id")
  private Integer userId;

  @Column(name = "user_name")
  private String name;

  @Column(name = "class_name")
  private String className;

  @Column(name = "age")
  private Integer age;

}

4、编写mapper

public interface UserMapper extends JpaRepository<User, Integer> {

  List<User> findUsersByName(String name);

  List<User>  findByAgeAndName(Integer age, String name);
}

5、编写测试类

@SpringBootTest
class SpringbootjpaApplicationTests {

  @Autowired
  private UserMapper userMapper;

  /**
   * 使用jpa自带的方法，向数据库中添加数据
   */
  @Test
  void contextLoads() {

    userMapper.save(buildUser("mobian", "初一", 13));
    userMapper.save(buildUser("pan", "高一", 22));
    userMapper.save(buildUser("wang", "初二", 15));
  }

  private static User buildUser(String name, String className, Integer age) {
    User user = new User();
    user.setClassName(className);
    user.setName(name);
    user.setAge(age);
    return user;
  }

  /**
   * 使用jpa自带的方法，查询所有的数据，再分页后返回
   */

  @Test
  void findAll() {
    System.out.println(userMapper.findAll(PageRequest.of(1, 2)));
  }

  /**
   * 使用jpa自带的方法，根据主键id查询数据库数据
   */
  @Test
  void findAllById() {
    System.out.println(userMapper.findById(1));
  }

  /**
   * 使用mapper中自定义的方法，不需要写sql，直接根据方法命名规则完成sql逻辑
   */
  @Test
  void findAllByName() {
    System.out.println(userMapper.findUsersByName("mobian"));
  }

  /**
   * 使用mapper中自定义的方法，不需要写sql，直接根据方法命名规则完成sql逻辑
   */
  @Test
  void findAllByAge() {
    System.out.println(userMapper.findByAgeAndName(22, "pan"));
  }
}

附JPA支持的方法换sql的表格：

Keyword	Sample	JPQL snippet
`Distinct`	`findDistinctByLastnameAndFirstname`	`select distinct … where x.lastname = ?1 and x.firstname = ?2`
`And`	`findByLastnameAndFirstname`	`… where x.lastname = ?1 and x.firstname = ?2`
`Or`	`findByLastnameOrFirstname`	`… where x.lastname = ?1 or x.firstname = ?2`
`Is`, `Equals`	`findByFirstname`,`findByFirstnameIs`,`findByFirstnameEquals`	`… where x.firstname = ?1`
`Between`	`findByStartDateBetween`	`… where x.startDate between ?1 and ?2`
`LessThan`	`findByAgeLessThan`	`… where x.age < ?1`
`LessThanEqual`	`findByAgeLessThanEqual`	`… where x.age <= ?1`
`GreaterThan`	`findByAgeGreaterThan`	`… where x.age > ?1`
`GreaterThanEqual`	`findByAgeGreaterThanEqual`	`… where x.age >= ?1`
`After`	`findByStartDateAfter`	`… where x.startDate > ?1`
`Before`	`findByStartDateBefore`	`… where x.startDate < ?1`
`IsNull`, `Null`	`findByAge(Is)Null`	`… where x.age is null`
`IsNotNull`, `NotNull`	`findByAge(Is)NotNull`	`… where x.age not null`
`Like`	`findByFirstnameLike`	`… where x.firstname like ?1`
`NotLike`	`findByFirstnameNotLike`	`… where x.firstname not like ?1`
`StartingWith`	`findByFirstnameStartingWith`	`… where x.firstname like ?1` (parameter bound with appended `%`)
`EndingWith`	`findByFirstnameEndingWith`	`… where x.firstname like ?1` (parameter bound with prepended `%`)
`Containing`	`findByFirstnameContaining`	`… where x.firstname like ?1` (parameter bound wrapped in `%`)
`OrderBy`	`findByAgeOrderByLastnameDesc`	`… where x.age = ?1 order by x.lastname desc`
`Not`	`findByLastnameNot`	`… where x.lastname <> ?1`
`In`	`findByAgeIn(Collection<Age> ages)`	`… where x.age in ?1`
`NotIn`	`findByAgeNotIn(Collection<Age> ages)`	`… where x.age not in ?1`
`True`	`findByActiveTrue()`	`… where x.active = true`
`False`	`findByActiveFalse()`	`… where x.active = false`
`IgnoreCase`	`findByFirstnameIgnoreCase`	`… where UPPER(x.firstname) = UPPER(?1)`