您好,登錄后才能下訂單哦!
這篇文章主要講解了“jpa EntityManager復雜查詢怎么實現(xiàn)”,文中的講解內(nèi)容簡單清晰,易于學習與理解,下面請大家跟著小編的思路慢慢深入,一起來研究和學習“jpa EntityManager復雜查詢怎么實現(xiàn)”吧!
EntityManager
:EntityManager是JPA中用于增刪改查的接口,它的作用相當于一座橋梁,連接內(nèi)存中的java對象和數(shù)據(jù)庫的數(shù)據(jù)存儲??梢杂胓etCriteriaBuilder()的方式獲取CriteriaBuilder對象。
CriteriaBuilder
接口:用于構造標準查詢、復合條件、表達式、排序等。可以通過createQuery的方式獲取CriteriaQuery實例。
CriteriaQuery
接口:代表一個specific的頂層查詢對象,它包含著查詢的各個部分,比如:select 、from、where、group by、order by。
Root
接口:代表Criteria查詢的根對象,定義了實體類型,能為將來導航獲得想要的結果,它與SQL查詢中的FROM子句類似
接下來上代碼啦!
@PersistenceContext private EntityManager em;
CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<ADTO> q = cb.createQuery(ADTO.class); Root<A> root = q.from(A.class); /*********************表連接**************************/ Join<A, B> b = root.join("b", JoinType.LEFT); Join<A, C> c = root.join("c", JoinType.LEFT); Join<A, D> d = root.join("d", JoinType.LEFT); Join<A, E> e = root.join("e", JoinType.LEFT); Join<A, F> f = root.join("f", JoinType.LEFT); q.multiselect(//備注:ADTO要有對應構造函數(shù)哦 root.get("id"), root.get("version"), root.get("code"), root.get("name"), root.get("isAlterable"), root.get("mustCharge"), root.get("isConsignment"), root.get("memo"), b.get("id"), b.get("name"), c.get("id"), c.get("description"), d.get("id"), d.get("name"), e.get("id"), e.get("name"), f.get("id"), f.get("name"), root.get("standardPrice"), root.get("upperPrice"), root.get("lowerPrice"), root.get("isActive") );//還可以進行where.order by等操作哦 List<ADTO> rs = em.createQuery(q).getResultList();
到此就完成啦?。?!
where條件
List<Predicate> predicates = new ArrayList<>(); CriteriaBuilder.In<String> in = cb.in(root.get("code").as(String.class)); for (String code: codes) { in.value(code); } predicates.add(in); if (startDate != null && !"".equals(startDate)) { predicateList.add(cb.greaterThan(birthdayPath, startDate)); } Predicate[] pre = new Predicate[predicates.size()]; q.where(predicates.toArray(pre));
or 條件拼接
public List<Predicate> getOrSearchPredicates(CriteriaBuilder cb, Root<T> root, String keywords){ List<Predicate> predicates = new ArrayList<>(); Predicate predicate = null; Predicate predicate1 = null; try { UUID uuid = UUID.fromString(keywords); predicate1 = cb.equal(root.get("id"), uuid); }catch (Exception e){ log.info(e.getMessage()); }finally { Predicate predicate2 = cb.like(root.get("code"), "%"+keywords+"%"); Predicate predicate3 = cb.like(root.get("name"), "%"+keywords+"%"); if (predicate1 != null){ predicate = cb.or(predicate1, cb.or(predicate2,predicate3)); } else { predicate = cb.or(predicate2, predicate3); } } predicates.add(predicate); return predicates; }
JPA 動態(tài)更新
CriteriaBuilder cb=entityManager.getCriteriaBuilder(); CriteriaUpdate<T> op=cb.createCriteriaUpdate(clazz); Root<T> root=op.from(clazz); op.set(fieldName, value); op.where(cb.equal(root.get(keyName), delta.get(keyName))); entityManager.createQuery(op).executeUpdate();
CriteriaBuilder cb = entityManager.getCriteriaBuilder(); CriteriaQuery<User> cq = cb.createQuery(User.class); Root<User> root = cq.from(User.class); //from User cq.select(root); //select * from User javax.persistence.criteria.Predicate pre = cb.equal(root.get("id").as(Integer.class),id);//id=1 cq.where(pre);//where id=1 Query query = entityManager.createQuery(cq);//select u from User u where u.id = 1 System.out.println(query.getResultList());
public Predicate toPredicate(Root<RoleEntity> root, CriteriaQuery<?> query, CriteriaBuilder cb) { List<Predicate> list = new ArrayList<Predicate>(); list.add(cb.equal(root.get("dr").as(Integer.class), delete)); if (StringUtils.isNotBlank(searchParam)) {/*searchParam 為傳遞參數(shù)*/ list.add(cb.or(cb.like(root.get("roleName").as(String.class), cb.literal("%" + searchParam + "%")), cb.like(root.get("roleCode").as(String.class), cb.literal("%" + searchParam + "%")))); } // 角色id if (roleId != null && !("".equals(roleId.trim()))) { list.add(cb.equal(root.get("id").as(String.class), roleId)); } // 管理員角色標識 if (category != null && category > 0) { list.add(cb.equal(root.get("category").as(Integer.class), category)); } //多角色Id if (roleids != null && roleids.size() > 0) { list.add(root.get("id").as(String.class).in(roleids)); } Predicate[] predicates = new Predicate[list.size()]; query.where(list.toArray(predicates)); query.orderBy(cb.asc(root.get("roleType").as(String.class)), cb.asc(root.get("roleProperty").as(String.class)), cb.asc(root.get("roleCode").as(String.class))); return query.getRestriction(); }
參考 org.springframework.data.jpa.repository.support.SimpleJpaRepository 的 findAll方法,如下
public List<T> findAll(Specification<T> spec) { return getQuery(spec, (Sort) null).getResultList(); } protected TypedQuery<T> getQuery(Specification<T> spec, Sort sort) { CriteriaBuilder builder = em.getCriteriaBuilder(); CriteriaQuery<T> query = builder.createQuery(getDomainClass()); Root<T> root = applySpecificationToCriteria(spec, query); query.select(root); if (sort != null) { query.orderBy(toOrders(sort, root, builder)); } return applyRepositoryMethodMetadata(em.createQuery(query)); } private TypedQuery<T> applyRepositoryMethodMetadata(TypedQuery<T> query) { if (metadata == null) { return query; } LockModeType type = metadata.getLockModeType(); TypedQuery<T> toReturn = type == null ? query : query.setLockMode(type); applyQueryHints(toReturn); return toReturn; }
感謝各位的閱讀,以上就是“jpa EntityManager復雜查詢怎么實現(xiàn)”的內(nèi)容了,經(jīng)過本文的學習后,相信大家對jpa EntityManager復雜查詢怎么實現(xiàn)這一問題有了更深刻的體會,具體使用情況還需要大家實踐驗證。這里是億速云,小編將為大家推送更多相關知識點的文章,歡迎關注!
免責聲明:本站發(fā)布的內(nèi)容(圖片、視頻和文字)以原創(chuàng)、轉(zhuǎn)載和分享為主,文章觀點不代表本網(wǎng)站立場,如果涉及侵權請聯(lián)系站長郵箱:is@yisu.com進行舉報,并提供相關證據(jù),一經(jīng)查實,將立刻刪除涉嫌侵權內(nèi)容。