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

Posted 2021-03-06

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);

测试类

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

@RunWith(SpringRunner.class)br/>@SpringBootTest
public class UserPagingRepositoryTest {

/**
 * ?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,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("张三", 16,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("三哥", 12,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("米二", 13,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("阿三", 12,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("张三", 12,"[e-mail]")));
    logger.info("新增数据 result = {}", userPagingRepository.save(new User("米二", 8,"[e-mail]")));
}

@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","[e-mail]"));
    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 id10, user0_.age as age20, user0_.email as email30, user0_.name as name40 from user user0 where user0.name=?
通过姓名查找(findByName) result = [User{id=2, name=‘张三‘, age=16, email=‘[e-mail]‘}, User{id=6, name=‘张三‘, age=12, email=‘[e-mail]‘}]

Hibernate: select user0_.id as id10, user0_.age as age20, user0_.email as email30, user0_.name as name40 from user user0 where user0.name=?
通过姓名查找(queryByName) result = [User{id=2, name=‘张三‘, age=16, email=‘[e-mail]‘}, User{id=6, name=‘张三‘, age=12, email=‘[e-mail]‘}]

Hibernate: select user0_.id as id10, user0_.age as age20, user0_.email as email30, user0_.name as name40 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=‘[e-mail]‘}, User{id=5, name=‘阿三‘, age=12, email=‘[e-mail]‘}, User{id=6, name=‘张三‘, age=12, email=‘[e-mail]‘}]

Hibernate: select count(user0_.id) as col_00 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=‘[e-mail]‘}, User{id=6, name=‘张三‘, age=12, email=‘[e-mail]‘}]
2020-02-29 17:02:37.431 INFO 48944 --- [ main] c.m.c.r.UserPagingRepositoryTest : ---------------------------------
Hibernate: select user0_.id as id10, user0_.age as age20, user0_.email as email30, user0_.name as name40 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=‘[e-mail]‘}, User{id=4, name=‘米二‘, age=13, email=‘[e-mail]‘}, User{id=3, name=‘三哥‘, age=12, email=‘[e-mail]‘}, User{id=5, name=‘阿三‘, age=12, email=‘[e-mail]‘}, User{id=6, name=‘张三‘, age=12, email=‘[e-mail]‘}, User{id=1, name=‘小米‘, age=9, email=‘[e-mail]‘}, User{id=7, name=‘米二‘, age=8, email=‘[e-mail]‘}]
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)br/>@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, "[e-mail]");
    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。

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