Spring Data JPA的简单使用

Posted 2023-02-22 默辨

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)