[TOC]

基本使用方法

继承接口并声明查询方法

interface PersonRepository extends Repository<Person, Long> {
   List<Person> findByLastname(String lastname);
}

Autowired注入

public class SomeClient {
 
  @Autowired
  private PersonRepository repository;
 
  public void doSomething() {
    List<Person> persons = repository.findByLastname("Matthews");
  }
}

自定义Repository

选择性暴露CURD方法

@NoRepositoryBean
interface MyBaseRepository<T, ID extends Serializable> extends Repository<T, ID> {
 
  T findOne(ID id);
 
  T save(T entity);
}
 
interface UserRepository extends MyBaseRepository<User, Long> {
  User findByEmailAddress(EmailAddress emailAddress);
}

使用特定模块接口定义Repository

interface MyRepository extends JpaRepository<User, Long> { }
 
@NoRepositoryBean
interface MyBaseRepository<T, ID extends Serializable> extends JpaRepository<T, ID> {
  …
}
 
interface UserRepository extends MyBaseRepository<User, Long> {
  …
}

注意：中间层repository接口要使用注解@NoRepositoryBean，以确保Spring Data不会在运行时对其实例化。

定义查询方法

查询方法建立

1. distinct flag
2. ignoring case
3. order by

public interface PersonRepository extends Repository<User, Long> {
 
  List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);
 
  // Enables the distinct flag for the query
  List<Person> findDistinctPeopleByLastnameOrFirstname(String lastname, String firstname);
  List<Person> findPeopleDistinctByLastnameOrFirstname(String lastname, String firstname);
 
  // Enabling ignoring case for an individual property
  List<Person> findByLastnameIgnoreCase(String lastname);
  // Enabling ignoring case for all suitable properties
  List<Person> findByLastnameAndFirstnameAllIgnoreCase(String lastname, String firstname);
 
  // Enabling static ORDER BY for a query
  List<Person> findByLastnameOrderByFirstnameAsc(String lastname);
  List<Person> findByLastnameOrderByFirstnameDesc(String lastname);
}

为了消除不确定性，可以在方法名内使用下划线“_”手动定义隔断点。

List<Person> findByAddress_ZipCode(ZipCode zipCode);

特殊参数处理

Page<User> findByLastname(String lastname, Pageable pageable);
 
Slice<User> findByLastname(String lastname, Pageable pageable);
 
List<User> findByLastname(String lastname, Sort sort);
 
List<User> findByLastname(String lastname, Pageable pageable);

限制查询结果数量

User findFirstByOrderByLastnameAsc();
 
User findTopByOrderByAgeDesc();
 
Page<User> queryFirst10ByLastname(String lastname, Pageable pageable);
 
Slice<User> findTop3ByLastname(String lastname, Pageable pageable);
 
List<User> findFirst10ByLastname(String lastname, Sort sort);
 
List<User> findTop10ByLastname(String lastname, Pageable pageable);

流式查询结果

@Query("select u from User u")
Stream<User> findAllByCustomQueryAndStream();
 
Stream<User> readAllByFirstnameNotNull();
 
@Query("select u from User u")
Stream<User> streamAllPaged(Pageable pageable);

流在使用结束后需要关闭以释放资源，可以用 close() 方法手动将其关闭或者使用 try-with-resources 块。

• try-with-resources 块

try (Stream<User> stream = repository.findAllByCustomQueryAndStream()) {
  stream.forEach(…);
}

异步查询结果

1. 使用 java.util.concurrent.Future 作为返回类型
2. 使用 Java 8 java.util.concurrent.CompletableFuture 作为返回类型
3. 使用 org.springframework.util.concurrent.ListenableFuture 作为返回类型

@Async
Future<User> findByFirstname(String firstname);             
 
@Async
CompletableFuture<User> findOneByFirstname(String firstname);
 
@Async
ListenableFuture<User> findOneByLastname(String lastname);

关键字

使用 @Query

基本用法

public interface UserRepository extends JpaRepository<User, Long> {
 
  @Query("select u from User u where u.emailAddress = ?1")
  User findByEmailAddress(String emailAddress);
}

使用 LIKE 表达式

public interface UserRepository extends JpaRepository<User, Long> {
 
  @Query("select u from User u where u.firstname like %?1")
  List<User> findByFirstnameEndsWith(String firstname);
}

使用原生SQL

public interface UserRepository extends JpaRepository<User, Long> {
 
  @Query(value = "SELECT * FROM USERS WHERE EMAIL_ADDRESS = ?1", nativeQuery = true)
  User findByEmailAddress(String emailAddress);
}

原生SQL分页

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);
}

使用 Sort 和 JpaSort

public interface UserRepository extends JpaRepository<User, Long> {
 
  @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);
}
 
repo.findByAndSort("lannister", new Sort("firstname"));             
repo.findByAndSort("stark", new Sort("LENGTH(firstname)"));         
repo.findByAndSort("targaryen", JpaSort.unsafe("LENGTH(firstname)"));
repo.findByAsArrayAndSort("bolton", new Sort("fn_len"));             

使用已命名参数

public interface UserRepository extends JpaRepository<User, Long> {
 
  @Query("select u from User u where u.firstname = :firstname or u.lastname = :lastname")
  User findByLastnameOrFirstname(@Param("lastname") String lastname,
                                 @Param("firstname") String firstname);
}

修改查询

@Modifying
@Query("update User u set u.firstname = ?1 where u.lastname = ?2")
int setFixedFirstnameFor(String firstname, String lastname);