SpringData JPA利用Specification多条件查询

SpringData JPA遵循Eric Evans在

Domain Driver Design

快速开始

关于SpringBoot与JPA的快速整合，已经在这篇文章中写的非常详细：SpringBoot整合Spring Data JPA，一些配置部分就不再赘述了，我们直接创建一个条件丰富一些的实体类做测试。

创建实体类

@Entity(name = "t_blog")
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Blog implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

/**
* 文章名称
*/
private String name;
/**
* 作者
*/
private String author;

/**
* 状态, 0代表未发布, 1代表已发布
*/
private Integer status;

/**
* 发布时间
*/
@Column(name = "publish_time")
private Date publishTime;

/**
* 更新时间
*/
@Column(name = "update_time")
private Date updateTime;

}

继承JpaSpecificationExecutor接口

public interface BlogDao extends JpaRepository<Blog, Long>, JpaSpecificationExecutor<Blog> {
}

继承

JpaSpecificationExecutor

Specification

public interface JpaSpecificationExecutor<T> {
Optional<T> findOne(@Nullable Specification<T> spec);
List<T> findAll(@Nullable Specification<T> spec);
Page<T> findAll(@Nullable Specification<T> spec, Pageable pageable);
List<T> findAll(@Nullable Specification<T> spec, Sort sort);
long count(@Nullable Specification<T> spec);
}

Specification接口

可以看到，他们都需要一个Specification接口对象，而且可以注意到这个接口中有Java8新增的接口规范，如static方法、default方法，以及仅有一个抽象方法，可以作为函数式接口，传入Lambda表达式简化书写。

这些方法的用法其实见名知义对吧。

public interface Specification<T> extends Serializable {

long serialVersionUID = 1L;

static <T> Specification<T> not(@Nullable Specification<T> spec) {

return spec == null //
? (root, query, builder) -> null //
: (root, query, builder) -> builder.not(spec.toPredicate(root, query, builder));
}

static <T> Specification<T> where(@Nullable Specification<T> spec) {
return spec == null ? (root, query, builder) -> null : spec;
}

default Specification<T> and(@Nullable Specification<T> other) {
return SpecificationComposition.composed(this, other, CriteriaBuilder::and);
}

default Specification<T> or(@Nullable Specification<T> other) {
return SpecificationComposition.composed(this, other, CriteriaBuilder::or);
}

@Nullable
Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder);
}

复杂查询

@Test
public void findByExample() {
Specification<Blog> specification = new Specification<Blog>() {
@Override
public Predicate toPredicate(Root<Blog> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
List<Predicate> predicates = new LinkedList<>();
predicates.add(cb.equal(root.get("status"), 1)); // 查询status状态为1
predicates.add(cb.like(root.get("author"), "%summer%")); // author名称中存在summer
predicates.add(cb.between(root.get("publishTime"),  // 发布时间7天前至今
Date.from(Instant.now().minus(Duration.ofDays(7))), new Date()));

return query.where(predicates.toArray(new Predicate[0])).getRestriction();
}
};
// 按照条件查询,并按照publish_time升序
List<Blog> blogs
= blogDao.findAll(specification, Sort.by(Sort.Direction.ASC, "publishTime"));
blogs.forEach(System.out::println);
}

最后的查询语句如下：

se
56c
lect id, author, name,publish_time,status,update_time from t_blog
where status = 1 and (author like ?)
and (publish_time between ? and ?)
order by publish_time asc

参考阅读

• https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#reference