【Spring Data 系列学习】Spring Data JPA 自定义查询，分页，排序，条件查询

Spring Boot Jpa 默认提供 CURD 的方法等方法，在日常中往往时无法满足我们业务的要求，本章节通过自定义简单查询案例进行讲解。

快速上手

项目中的pom.xml、application.properties与 Chapter1 相同

实体类映射数据库表

user 实体类

@Entity
public class User implements Serializable {

    private static final long serialVersionUID = -390763540622907853L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private Integer age;

    private String email;

    // 省略构造器 set/get		

}

自定义简单查询

spring data 内部基础架构中有个根据方法名的查询生成器机制，对于在存储库的实体上构建约束查询很有用。该机制方法的前缀有find…By、read…By、query…By、count…By和get…By，从这些方法可以分析它的其余部分（实体里面的字段）。引入子句可以包含其他表达式，例如在Distinct要创建的查询上设置不同的标志。然而，第一个By作为分隔符来指示实际标准的开始。在一个非常基本的水平上，你可以定义实体性条件，并与它们串联（And和Or）。

注：此段来自 《Spring Data JPA 从入门到精通》。

继承 PagingAndSortingRepository

public interface UserPagingRepository extends PagingAndSortingRepository<User, Long> {
    // 通过姓名查找
    List<User> findByName(String name);

    // 通过姓名查找
    List<User> queryByName(String name);

    // 通过姓名或者邮箱查找
    List<User> findByNameOrEmail(String name,String email);

    // 计算某一个 age 的数量
    int countByAge(int age);
}

测试类

路径：src/test/java/com/mtcarpenter/chapter2/repository/UserPagingRepositoryTest.java

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserPagingRepositoryTest {

    /**
     * ⽇志对象
     */
    private Logger logger = LoggerFactory.getLogger(UserPagingRepositoryTest.class);

    @Autowired
    private UserPagingRepository userPagingRepository;

    @Before
    public void save() {
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("小米", 9,"a@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("张三", 16,"b@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("三哥", 12,"c@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("米二", 13,"e@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("阿三", 12,"f@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("张三", 12,"g@qq.com")));
        logger.info("新增数据 result = {}", userPagingRepository.save(new User("米二", 8,"h@qq.com")));
    }

    @Test
    public void find(){
        logger.info("通过姓名查找(findByName) result = {}", userPagingRepository.findByName("张三"));
        logger.info("通过姓名查找(queryByName) result = {}", userPagingRepository.queryByName("张三"));
        logger.info("通过姓名或者邮箱(findByNameOrEmail)  查找 result = {}", userPagingRepository.findByNameOrEmail("张三","f@qq.com"));
        logger.info("通过某一个 age 的数量(countByAge) result = {}", userPagingRepository.countByAge(12));
    }

}

@Before会在@test之前运行。

输出日志：

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.email as email3_0_, user0_.name as name4_0_ from user user0_ where user0_.name=?
通过姓名查找(findByName) result = [User{id=2, name='张三', age=16, email='b@qq.com'}, User{id=6, name='张三', age=12, email='g@qq.com'}]

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.email as email3_0_, user0_.name as name4_0_ from user user0_ where user0_.name=?
通过姓名查找(queryByName) result = [User{id=2, name='张三', age=16, email='b@qq.com'}, User{id=6, name='张三', age=12, email='g@qq.com'}]

Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.email as email3_0_, user0_.name as name4_0_ from user user0_ where user0_.name=? or user0_.email=?
通过姓名或者邮箱(findByNameOrEmail)  查找 result = [User{id=2, name='张三', age=16, email='b@qq.com'}, User{id=5, name='阿三', age=12, email='f@qq.com'}, User{id=6, name='张三', age=12, email='g@qq.com'}]

Hibernate: select count(user0_.id) as col_0_0_ from user user0_ where user0_.age=?
通过某一个 age 的数量(countByAge) result = 3

日志比较冗余删除了多余日志，从日志中我们可以发现 JPA 根据我们定义的接口方法自动解析成 SQL

方法中支持的关键字如下

关键字	示例	JPQL 表达式
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 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)

分页和排序

数据分页和排序在日常也是必不可少的，在 Spring Boot Jpa 中使用分页和排序，需要在Repository 接口的方法中，传入Pageable 实例 。

public interface UserPagingRepository extends PagingAndSortingRepository<User, Long> {
   // 通过姓名条件查询
    List<User> findByName(String name, Pageable pageable);

}

测试方法

    @Test
    public void pageAndSort(){
        Sort sort = new Sort(Sort.Direction.DESC, "age");
        int page = 0;
        int size = 10;
        Pageable pageable = PageRequest.of(page, size, sort);
        logger.info("条件查询 result = {}", userPagingRepository.findByName("张三",pageable));
        logger.info("---------------------------------");
        logger.info("根据年龄排序 result = {}", userPagingRepository.findAll(sort));
    }

测试结果

2020-02-29 17:02:37.431  INFO 48944 --- [           main] c.m.c.r.UserPagingRepositoryTest         : 条件查询 result = [User{id=2, name='张三', age=16, email='b@qq.com'}, User{id=6, name='张三', age=12, email='g@qq.com'}]
2020-02-29 17:02:37.431  INFO 48944 --- [           main] c.m.c.r.UserPagingRepositoryTest         : ---------------------------------
Hibernate: select user0_.id as id1_0_, user0_.age as age2_0_, user0_.email as email3_0_, user0_.name as name4_0_ from user user0_ order by user0_.age desc
2020-02-29 17:02:37.459  INFO 48944 --- [           main] c.m.c.r.UserPagingRepositoryTest         : 根据年龄排序 result = [User{id=2, name='张三', age=16, email='b@qq.com'}, User{id=4, name='米二', age=13, email='e@qq.com'}, User{id=3, name='三哥', age=12, email='c@qq.com'}, User{id=5, name='阿三', age=12, email='f@qq.com'}, User{id=6, name='张三', age=12, email='g@qq.com'}, User{id=1, name='小米', age=9, email='a@qq.com'}, User{id=7, name='米二', age=8, email='h@qq.com'}]

复杂条件查询

前面演示了 CrudRepository 和 PagingAndSortingRepository ，下面通过继承 JpaRepository 和JpaSpecificationExecutor 操作更复杂的语句。

JpaSpecificationExecutor 是 JPA 2.0 提供的Criteria API，可以用于动态生成query。Spring Data JPA 支持 Criteria 查询，可以很方便地使用，足以应付工作中的所有复杂查询的情况了，可以对 JPA 实现最大限度的扩展。《spring data Jpa 从入门到精通》

public interface JpaSpecificationExecutor<T> {
    // 根据 Specification 条件查询单个对象
    Optional<T> findOne(@Nullable Specification<T> var1);
	// 根据 Specification 条件查询 返回 List 结果
    List<T> findAll(@Nullable Specification<T> var1);
	// 根据 Specification 条件 和 分页条件查询
    Page<T> findAll(@Nullable Specification<T> var1, Pageable var2);
	// 根据 Specification 条件 和 排序条件查询 返回 List 结果
    List<T> findAll(@Nullable Specification<T> var1, Sort var2);
	// 根据 Specification 条件查询数量
    long count(@Nullable Specification<T> var1);
}

UserJpaRepository 数据层接口

public interface UserJpaRepository extends JpaRepository<User,Long>, JpaSpecificationExecutor {
}

测试类

路径：src/test/java/com/mtcarpenter/chapter2/repository/UserJpaRepositoryTest.java

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserJpaRepositoryTest {

    @Test
    public void specification() {
        Specification specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb) {
                // like 模糊查询 ， root.get("name") 属性名  "%三%" 为三
                Predicate p1 = cb.like(root.get("name"), "%三%");
                // greaterThan 表示 age 大于 10
                Predicate p2 = cb.greaterThan(root.get("age"), 10);
                // cb.and(p1, p2) ，and 则表示 p1 和 p2 并且关系，除了 and 还有or, not等。点击  CriteriaBuilder 可进行查看
                return cb.and(p1, p2);
            }
        };

    }

    @Test
    public void ConditionalQuery() {
        int page = 0;
        int size = 10;
        Pageable pageable = PageRequest.of(page, size);
        // 模拟传入的条件
        User user = new User("三", 10, "b@qq.com");
        Specification specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                List<Predicate> predicates = new ArrayList<>();
                // 判断传入的值是否为空
                if (!"".equals(user.getName())) {
                    predicates.add(cb.like(root.get("name"), "%" + user.getName() + "%"));
                }
                // 判断年龄是否为空
                if (user.getAge() != null) {
                    predicates.add(cb.greaterThan(root.get("age"), user.getAge()));
                }

                return cb.and(predicates.toArray(new Predicate[predicates.size()]));
            }
        };
        Page result = userJpaRepository.findAll(specification, pageable);
        logger.info("条件查询 result = {}", result.getContent());
    }

}

specification() 方法更容易理解，如果看懂了此方法，有利于更了解ConditionalQuery() 方法。ConditionalQuery() 方法这种模式也是在实际开发中，使用的频率比较高的方法。

JpaSpecificationExecutor 通过 CriteriaQuery 几乎可以实现任何逻辑了。

本章代码

• Github：https://github.com/mtcarpenter/spring-data-chapter