1.Spring Data JPA是什么
由Spring提供的一个用于简化JPA开发的框架。可以在几乎不用写实现的情况下,实现对数据的访问和操作。除了CRUD外,还包括如分页、排序等一些常用的功能
Spring Data JPA的核心概念:
1:Repository:最顶层的接口,是一个空的接口,目的是为了统一所有Repository的类型,且能让组件扫描的时候自动识别。
2:CrudRepository :是Repository的子接口,提供CRUD的功能
3:PagingAndSortingRepository:是CrudRepository的子接口,添加分页和排序的功能
4:JpaRepository:是PagingAndSortingRepository的子接口,增加了一些实用的功能,比如:批量操作等。
5:JpaSpecificationExecutor:用来做负责查询的接口
6:Specification:是Spring Data JPA提供的一个查询规范,要做复杂的查询,只需围绕这个规范来设置查询条件即可
具体的关键字,使用方法和生产成SQL如下表所示
Keyword | Sample | JPQL snippet |
---|---|---|
And | findByLastnameAndFirstname | … where x.lastname = ?1 and x.firstname = ?2 |
Or | findByLastnameOrFirstname | … where x.lastname = ?1 or x.firstname = ?2 |
Is,Equals | 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 age) | … 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) |
2.与springboot整合
maven:
<dependency <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency>
gradle:
dependencies {
compile('org.springframework.boot:spring-boot-starter-data-jpa')
}
注:需要配置数据源
jpa可选配置
spring.jpa.database=
spring.jpa.show-sql=
spring.jpa.properties=
spring.jpa.generate-ddl=
spring.jpa.open-in-view=
spring.jpa.database-platform=
spring.jpa.hibernate.ddl-auto=
spring.data.jpa.repositories.enabled=
spring.jpa.hibernate.naming-strategy=
3.java代码
@NoRepositoryBean public interface DAOInterface<T> extends JpaRepository<T, String>, JpaSpecificationExecutor<T> { }
public interface JDCommodityRepository extends DAOInterface<JDCommodityBean> { /** * 分页查询商品 */ Page<JDCommodityBean> findAll(Specification<JDCommodityBean> spec, Pageable pageable); }
@Transactional(rollbackFor = Exception.class) @Service public class JDCommodityServiceImpl extends BaseService<JDCommodityBean> implements JDCommodityService { @PersistenceContext private EntityManager entityManager; @Autowired private JDCommodityRepository jdCommodityRepository; @Override public Page<JDCommodityBean> getJDCommodityListByPage(Integer pageNum, String name, String goodsCategory) { Specification<JDCommodityBean> spec = new Specification<JDCommodityBean>() { /** * 构造断言 * * @param root * 实体对象引用 * @param query * 规则查询对象 * @param cb * 规则构建对象 * @return 断言 */ @Override public Predicate toPredicate(Root<JDCommodityBean> root, CriteriaQuery<?> query, CriteriaBuilder cb) { List<Predicate> predicates = new ArrayList<>(); // 所有的断言集合 //默认 predicates.add(cb.equal(root.get("state").as(Integer.class), 1));// 上下架状态 1为上架,0为下架 predicates.add(cb.equal(root.get("saleState").as(Integer.class), 1));// 是否可售,1:是,0:否 predicates.add(cb.equal(root.get("isCanVAT").as(Integer.class), 1));// 是否可开增票,1:支持,0:不支持 predicates.add(cb.le(root.get("price").as(BigDecimal.class), 500));// 价格小于等于500 //自定义 // 商品名称 if(null != name && !"".equals(name) && !"''".equals(name) && name != "") { predicates.add(cb.like(root.get("name").as(String.class), "%" + name + "%")); } // 商品分类 if(goodsCategory != null && !"".equals(goodsCategory) && !"''".equals(goodsCategory)) { predicates.add(cb.equal(root.get("goodsCategory").as(String.class), goodsCategory)); } return cb.and(predicates.toArray(new Predicate[predicates.size()])); } }; Pageable pageable = new PageRequest(pageNum - 1, JDCommonConstant.COMMODITY_PAGE_SIZE);// 页码:前端从1开始,jpa从0开始 Page<JDCommodityBean> page = jdCommodityRepository.findAll(spec, pageable); return page; } @Override protected EntityManager getEntityManager() { return entityManager; } @Override protected DAOInterface<JDCommodityBean> getDAOInterface() { return jdCommodityRepository; } }