Spring Data JPA 在 SpringBoot 应用中的简单实践
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2022-04-22 08:02:29
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Spring Data JPA 在 SpringBoot 应用中的简单实践
1.引用maven依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
2.添加配置
添加@EnableJpaRepositories注解，开启JPA功能
@SpringBootApplication
@EnableJpaRepositories
public class SpringdataDemoApplication {
public static void main(String[] args) {
SpringApplication.run(SpringdataDemoApplication.class, args);
}
}
3.定义实体类
使用@Entity对实体类进行注解
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import javax.persistence.*;
@Entity(name = "t_user")
@NoArgsConstructor
@AllArgsConstructor
@Builder
@Data
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
@Column(name = "`t_name`")
private String name;
/**
* 不使用 @Column ，默认数据库字段名就是 age
*/
private Integer age;
/**
* 枚举
*/
@Enumerated(EnumType.STRING)
UserStatus status;
}
4.仓库类
4.1 基本仓库 Repository
import org.springframework.data.repository.Repository;
public interface UserRepository extends Repository<User, Long> {
}
这样就可以使用UserRepository就是持久化操作了，
但是若仅仅继承Repository接口，需要自己编写很多方法。
4.2 CrudRepository
CrudRepository接口封装了常用的增删改查方法：
@NoRepositoryBean
public interface CrudRepository<T, ID> extends Repository<T, ID> {
<S extends T> S save(S entity);
<S extends T> Iterable<S> saveAll(Iterable<S> entities);
Optional<T> findById(ID id);
boolean existsById(ID id);
Iterable<T> findAll();
Iterable<T> findAllById(Iterable<ID> ids);
long count();
void deleteById(ID id);
void delete(T entity);
void deleteAll(Iterable<? extends T> entities);
void deleteAll();
}
使用案例：
import org.springframework.data.repository.CrudRepository;
public interface UserRepository extends CrudRepository<User, Long> {
}
4.3 PagingAndSortingRepository
PagingAndSortingRepository提供了基本的分页方法，并继承了CrudRepository提供的增删改查方法
@NoRepositoryBean
public interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> {
Iterable<T> findAll(Sort sort);
Page<T> findAll(Pageable pageable);
}
使用案例：
import org.springframework.data.repository.PagingAndSortingRepository;
public interface UserRepository extends PagingAndSortingRepository<User, Long> {
}
4.4 JpaRepository
/**
* JPA specific extension of {@link org.springframework.data.repository.Repository}.
*
* @author Oliver Gierke
* @author Christoph Strobl
* @author Mark Paluch
*/
@NoRepositoryBean
public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
/*
* (non-Javadoc)
* @see org.springframework.data.repository.CrudRepository#findAll()
*/
List<T> findAll();
/*
* (non-Javadoc)
* @see org.springframework.data.repository.PagingAndSortingRepository#findAll(org.springframework.data.domain.Sort)
*/
List<T> findAll(Sort sort);
/*
* (non-Javadoc)
* @see org.springframework.data.repository.CrudRepository#findAll(java.lang.Iterable)
*/
List<T> findAllById(Iterable<ID> ids);
/*
* (non-Javadoc)
* @see org.springframework.data.repository.CrudRepository#save(java.lang.Iterable)
*/
<S extends T> List<S> saveAll(Iterable<S> entities);
/**
* Flushes all pending changes to the database.
*/
void flush();
/**
* Saves an entity and flushes changes instantly.
*
* @param entity
* @return the saved entity
*/
<S extends T> S saveAndFlush(S entity);
/**
* Deletes the given entities in a batch which means it will create a single {@link Query}. Assume that we will clear
* the {@link javax.persistence.EntityManager} after the call.
*
* @param entities
*/
void deleteInBatch(Iterable<T> entities);
/**
* Deletes all entities in a batch call.
*/
void deleteAllInBatch();
/**
* Returns a reference to the entity with the given identifier. Depending on how the JPA persistence provider is
* implemented this is very likely to always return an instance and throw an
* {@link javax.persistence.EntityNotFoundException} on first access. Some of them will reject invalid identifiers
* immediately.
*
* @param id must not be {@literal null}.
* @return a reference to the entity with the given identifier.
* @see EntityManager#getReference(Class, Object) for details on when an exception is thrown.
*/
T getOne(ID id);
/*
* (non-Javadoc)
* @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example)
*/
@Override
<S extends T> List<S> findAll(Example<S> example);
/*
* (non-Javadoc)
* @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example, org.springframework.data.domain.Sort)
*/
@Override
<S extends T> List<S> findAll(Example<S> example, Sort sort);
}
/**
* Interface to allow execution of Query by Example {@link Example} instances.
*
* @param <T>
* @author Mark Paluch
* @author Christoph Strobl
* @since 1.12
*/
public interface QueryByExampleExecutor<T> {
/**
* Returns a single entity matching the given {@link Example} or {@literal null} if none was found.
*
* @param example must not be {@literal null}.
* @return a single entity matching the given {@link Example} or {@link Optional#empty()} if none was found.
* @throws org.springframework.dao.IncorrectResultSizeDataAccessException if the Example yields more than one result.
*/
<S extends T> Optional<S> findOne(Example<S> example);
/**
* Returns all entities matching the given {@link Example}. In case no match could be found an empty {@link Iterable}
* is returned.
*
* @param example must not be {@literal null}.
* @return all entities matching the given {@link Example}.
*/
<S extends T> Iterable<S> findAll(Example<S> example);
/**
* Returns all entities matching the given {@link Example} applying the given {@link Sort}. In case no match could be
* found an empty {@link Iterable} is returned.
*
* @param example must not be {@literal null}.
* @param sort the {@link Sort} specification to sort the results by, must not be {@literal null}.
* @return all entities matching the given {@link Example}.
* @since 1.10
*/
<S extends T> Iterable<S> findAll(Example<S> example, Sort sort);
/**
* Returns a {@link Page} of entities matching the given {@link Example}. In case no match could be found, an empty
* {@link Page} is returned.
*
* @param example must not be {@literal null}.
* @param pageable can be {@literal null}.
* @return a {@link Page} of entities matching the given {@link Example}.
*/
<S extends T> Page<S> findAll(Example<S> example, Pageable pageable);
/**
* Returns the number of instances matching the given {@link Example}.
*
* @param example the {@link Example} to count instances for. Must not be {@literal null}.
* @return the number of instances matching the {@link Example}.
*/
<S extends T> long count(Example<S> example);
/**
* Checks whether the data store contains elements that match the given {@link Example}.
*
* @param example the {@link Example} to use for the existence check. Must not be {@literal null}.
* @return {@literal true} if the data store contains elements that match the given {@link Example}.
*/
<S extends T> boolean exists(Example<S> example);
}
使用案例：
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserRepository extends JpaRepository<User, Long> {
}
5.测试用例
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringdataDemoApplicationTests {
@Autowired
private UserRepository userRepository;
@Test
public void test1() {
User user = User.builder()
.name("gouzi")
.age(25)
.status(UserStatus.LEVEL1)
.build();
userRepository.save(user);
}
@Test
public void test2() {
//
userRepository.findAllByName("Tom").forEach(System.out::println);
}
}
6.自定义持久化语句
6.1 方法名方式
public interface UserRepository extends Repository<User, Long> {
long countByLastname(String lastname);
long deleteByLastname(String lastname);
List<User> removeByLastname(String lastname);
List<User> findByLastname(String lastname);
User findByEmailAddress(String emailAddress);
User findByEmailAddress(EmailAddress emailAddress);
User getByEmailAddress(EmailAddress emailAddress);
@Nullable
User findByEmailAddress(@Nullable EmailAddress emailAdress);
Optional<User> findOptionalByEmailAddress(EmailAddress emailAddress);
List<User> findByLastname(String lastname);
User findByEmailAddress(String emailAddress);
List<User> findByEmailAddressAndLastname(String emailAddress, String lastname);
}
拓展：
https://docs.spring.io/spring-data/jpa/docs/2.1.6.RELEASE/reference/html/#jpa.query-methods.query-creation#Table 3. Supported keywords inside method names
| 关键字 | 案例 | 含义 |
|---|---|---|
| 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 | findByAgeIsNull | … 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 ages) | … where x.age in ?1 |
| NotIn | findByAgeNotIn(Collection ages) | … where x.age not in ?1 |
| True | findByActiveTrue() | … where x.active = true |
| False | findByActiveFalse() | … where x.active = false |
| IgnoreCase | findByFirstnameIgnoreCase | … where UPPER(x.firstame) = UPPER(?1) |
6.2 编写SQL
public interface UserRepository extends JpaRepository<User, Long> {
@Query("select u from User u where u.emailAddress = ?1")
User findByEmailAddress(String emailAddress);
@Query("select u from User u where u.firstname like %?1")
List<User> findByFirstnameEndsWith(String firstname);
@Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?1", nativeQuery = true)
User findByEmailAddress(String emailAddress);
@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);
@Query("select u from User u where u.lastname like ?1%")
List<User> findByAndSort(String lastname, Sort sort);
@Query("select u.id, LENGTH(u.firstname) as fn_len from User u where u.lastname like ?1%")
List<Object[]> findByAsArrayAndSort(String lastname, Sort sort);
@Query("select u from User u where u.firstname = :firstname or u.lastname = :lastname")
User findByLastnameOrFirstname(@Param("lastname") String lastname,
@Param("firstname") String firstname);
@Query("select u from #{#entityName} u where u.lastname = ?1")
List<User> findByLastname(String lastname);
@Modifying
@Query("delete from User u where user.role.id = ?1")
void deleteInBulkByRoleId(long roleId);
@QueryHints(value = { @QueryHint(name = "name", value = "value")},
forCounting = false)
Page<User> findByLastname(String lastname, Pageable pageable);
@Override
@Transactional(timeout = 10)
public List<User> findAll();
@Modifying
@Transactional
@Query("delete from User u where u.active = false")
void deleteInactiveUsers();
// Plain query method
@Lock(LockModeType.READ)
List<User> findByLastname(String lastname);
// Redeclaration of a CRUD method
@Lock(LockModeType.READ);
List<User> findAll();
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