Spring Dtata JPA

1、 Spring Data JPA最近项目中使用了Spring Data JPA这套基于持久化层的一套查询规范( 即基于ORM和JPA )。今天自己整理一下这套“框架”的使用说明JPA:JPA全称Java Persistence API.JPA通过JDK 5.0注解或XML描述对象关系表的映射关系，并将运行期的实体对象持久化到数据库中。 使用Spring Data Jpa要引入相应的jar 文件。使用此规范只要实现几个重要的接口即可，首先看下这几个接口的关系那了解了接口之后该如何使用呢：public interface JPATests extends JpaRepository /如上面代码：

2、 jpaTests 是我自己创建的一个接口，该接口继承了JpaRepository 该接口引用泛型，T指该接口实现的实体类，ID是主键的类型。不用编写任何代码即可使用jpa带来的敏捷开发，对我们开发人员来说无疑是欣喜若狂。那这个接口都实现了哪些方法呢？你可以去Spring Data Jpa的源码中看，该接口有个实现里面就是它方法的实现逻辑算法：下面我贴出代码：Transactional(readOnly = true)public class SimpleJpaRepository implements JpaRepository,JpaSpecificationExecutor privat

3、e final JpaEntityInformation entityInformation;private final EntityManager em;private final PersistenceProvider provider;private LockMetadataProvider lockMetadataProvider;/* * Creates a new link SimpleJpaRepository to manage objects of the given link JpaEntityInformation. * * param entityInformation

4、 must not be literal null. * param entityManager must not be literal null. */public SimpleJpaRepository(JpaEntityInformation entityInformation, EntityManager entityManager) Assert.notNull(entityInformation);Assert.notNull(entityManager);this.entityInformation = entityInformation;this.em = entityMana

5、ger;vider = PersistenceProvider.fromEntityManager(entityManager);/* * Creates a new link SimpleJpaRepository to manage objects of the given domain type. * * param domainClass must not be literal null. * param em must not be literal null. */public SimpleJpaRepository(Class domainClass, Entity

6、Manager em) this(JpaEntityInformationSupport.getMetadata(domainClass, em), em);/* * Configures a custom link LockMetadataProvider to be used to detect link LockModeTypes to be applied to * queries. * * param lockMetadataProvider */public void setLockMetadataProvider(LockMetadataProvider lockMetadata

7、Provider) this.lockMetadataProvider = lockMetadataProvider;private Class getDomainClass() return entityInformation.getJavaType();private String getDeleteAllQueryString() return getQueryString(DELETE_ALL_QUERY_STRING, entityInformation.getEntityName();private String getCountQueryString() String count

8、Query = String.format(COUNT_QUERY_STRING, provider.getCountQueryPlaceholder(), %s);return getQueryString(countQuery, entityInformation.getEntityName();/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#delete(java.io.Serializable) */Transactionalpublic void delete(ID id) Ass

9、ert.notNull(id, The given id must not be null!);if (!exists(id) throw new EmptyResultDataAccessException(String.format(No %s entity with id %s exists!,entityInformation.getJavaType(), id), 1);delete(findOne(id);/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#delete(java.l

10、ang.Object) */Transactionalpublic void delete(T entity) Assert.notNull(entity, The entity must not be null!);em.remove(em.contains(entity) ? entity : em.merge(entity);/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#delete(java.lang.Iterable) */Transactionalpublic void del

11、ete(Iterable entities) Assert.notNull(entities, The given Iterable of entities not be null!);for (T entity : entities) delete(entity);/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository#deleteInBatch(java.lang.Iterable) */Transactionalpublic void deleteInBatch(Iterable ent

12、ities) Assert.notNull(entities, The given Iterable of entities not be null!);if (!entities.iterator().hasNext() return;applyAndBind(getQueryString(DELETE_ALL_QUERY_STRING, entityInformation.getEntityName(), entities, em).executeUpdate();/* * (non-Javadoc) * see org.springframework.data.repository.Re

13、pository#deleteAll() */Transactionalpublic void deleteAll() for (T element : findAll() delete(element);/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository#deleteAllInBatch() */Transactionalpublic void deleteAllInBatch() em.createQuery(getDeleteAllQueryString().executeUpdat

14、e();/* * (non-Javadoc) * * see * org.springframework.data.repository.Repository#readById(java.io.Serializable * ) */public T findOne(ID id) Assert.notNull(id, The given id must not be null!);return em.find(getDomainClass(), id);/* * (non-Javadoc) * see org.springframework.data.repository.CrudReposit

15、ory#exists(java.io.Serializable) */public boolean exists(ID id) Assert.notNull(id, The given id must not be null!);if (entityInformation.getIdAttribute() != null) String placeholder = provider.getCountQueryPlaceholder();String entityName = entityInformation.getEntityName();Iterable idAttributeNames

16、= entityInformation.getIdAttributeNames();String existsQuery = QueryUtils.getExistsQueryString(entityName, placeholder, idAttributeNames);TypedQuery query = em.createQuery(existsQuery, Long.class);if (entityInformation.hasCompositeId() for (String idAttributeName : idAttributeNames) query.setParamet

17、er(idAttributeName, entityInformation.getCompositeIdAttributeValue(id, idAttributeName); else query.setParameter(idAttributeNames.iterator().next(), id);return query.getSingleResult() = 1L; else return findOne(id) != null;/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository

18、#findAll() */public List findAll() return getQuery(null, (Sort) null).getResultList();/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#findAll(ID) */public List findAll(Iterable ids) return getQuery(new Specification() public Predicate toPredicate(Root root, CriteriaQuery

19、query, CriteriaBuilder cb) Path path = root.get(entityInformation.getIdAttribute();return path.in(cb.parameter(Iterable.class, ids);, (Sort) null).setParameter(ids, ids).getResultList();/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository#findAll(org.springframework.data.do

20、main.Sort) */public List findAll(Sort sort) return getQuery(null, sort).getResultList();/* * (non-Javadoc) * see org.springframework.data.repository.PagingAndSortingRepository#findAll(org.springframework.data.domain.Pageable) */public Page findAll(Pageable pageable) if (null = pageable) return new P

21、ageImpl(findAll();return findAll(null, pageable);/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaSpecificationExecutor#findOne(org.springframework.data.jpa.domain.Specification) */public T findOne(Specification spec) try return getQuery(spec, (Sort) null).getSingleResult(); catch

22、 (NoResultException e) return null;/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaSpecificationExecutor#findAll(org.springframework.data.jpa.domain.Specification) */public List findAll(Specification spec) return getQuery(spec, (Sort) null).getResultList();/* * (non-Javadoc) * se

23、e org.springframework.data.jpa.repository.JpaSpecificationExecutor#findAll(org.springframework.data.jpa.domain.Specification, org.springframework.data.domain.Pageable) */public Page findAll(Specification spec, Pageable pageable) TypedQuery query = getQuery(spec, pageable);return pageable = null ? ne

24、w PageImpl(query.getResultList() : readPage(query, pageable, spec);/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaSpecificationExecutor#findAll(org.springframework.data.jpa.domain.Specification, org.springframework.data.domain.Sort) */public List findAll(Specification spec, Sort

25、 sort) return getQuery(spec, sort).getResultList();/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#count() */public long count() return em.createQuery(getCountQueryString(), Long.class).getSingleResult();/* * (non-Javadoc) * see org.springframework.data.jpa.repository.Jpa

26、SpecificationExecutor#count(org.springframework.data.jpa.domain.Specification) */public long count(Specification spec) return getCountQuery(spec).getSingleResult();/* * (non-Javadoc) * see org.springframework.data.repository.CrudRepository#save(java.lang.Object) */Transactionalpublic S save(S entity

27、) if (entityInformation.isNew(entity) em.persist(entity);return entity; else return em.merge(entity);/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository#saveAndFlush(java.lang.Object) */Transactionalpublic T saveAndFlush(T entity) T result = save(entity);flush();return res

28、ult;/* * (non-Javadoc) * see org.springframework.data.jpa.repository.JpaRepository#save(java.lang.Iterable) */Transactionalpublic List save(Iterable entities) List result = new ArrayList();if (entities = null) return result;for (S entity : entities) result.add(save(entity);return result;/* * (non-Ja

29、vadoc) * see org.springframework.data.jpa.repository.JpaRepository#flush() */Transactionalpublic void flush() em.flush();/* * Reads the given link TypedQuery into a link Page applying the given link Pageable and * link Specification. * * param query must not be literal null. * param spec can be lite

30、ral null. * param pageable can be literal null. * return */private Page readPage(TypedQuery query, Pageable pageable, Specification spec) query.setFirstResult(pageable.getOffset();query.setMaxResults(pageable.getPageSize();Long total = QueryUtils.executeCountQuery(getCountQuery(spec);List content =

31、total pageable.getOffset() ? query.getResultList() : Collections. emptyList();return new PageImpl(content, pageable, total);/* * Creates a new link TypedQuery from the given link Specification. * * param spec can be literal null. * param pageable can be literal null. * return */private TypedQuery ge

32、tQuery(Specification spec, Pageable pageable) Sort sort = pageable = null ? null : pageable.getSort();return getQuery(spec, sort);/* * Creates a link TypedQuery for the given link Specification and link Sort. * * param spec can be literal null. * param sort can be literal null. * return */private Ty

33、pedQuery getQuery(Specification spec, Sort sort) CriteriaBuilder builder = em.getCriteriaBuilder();CriteriaQuery query = builder.createQuery(getDomainClass();Root root = applySpecificationToCriteria(spec, query);query.select(root);if (sort != null) query.orderBy(toOrders(sort, root, builder);return applyLockMode(em.createQuery(query);/* * Creates a new count query for the given link Specification. * * param spec can be literal null. * return */private TypedQuery getCountQuery(Specification spec) CriteriaBuilde