八、JpaSpecificationExecutor接口
前言：該接口主要提供了多條件查詢的支持，并且可以在查詢中添加分頁(yè)和排序。
注意：JpaSpecificationExecutor接口是獨(dú)立存在的。完全獨(dú)立。

1、持久層接口：

public interface UsersRepositorySpecification extends JpaRepository<Users,Integer>, JpaSpecificationExecutor<Users> { }

測(cè)試代碼

@RunWith(SpringRunner.class) @SpringBootTest public class UsersRepositorySpecificationTest {@Autowiredprivate UsersRepositorySpecification usersRepositorySpecification;/*** jpaSpecificationExecutor 接口 單條件測(cè)試*/@Testpublic void jpaSpecificationExecutor() {/*** Specification<Users> 用于封裝條件*/Specification<Users> spec = new Specification<Users>() {/*** Root<Users>:查詢對(duì)象屬性封裝* CriteriaQuery<?> query:瘋長(zhǎng)了我們要執(zhí)行的查詢中各個(gè)部分的信息，select from order* CriteriaBuilder:查詢條件的構(gòu)造器，定義不同查詢條件* @param root* @param query* @param criteriaBuilder* @return*/@Overridepublic Predicate toPredicate(Root<Users> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {/*** 參數(shù)1：查詢的屬性* 參數(shù)2：查詢的指*/Predicate pre = criteriaBuilder.equal(root.get("name"), "zhanga");return pre;}};List<Users> list = usersRepositorySpecification.findAll(spec);for (Users users : list) {System.out.println(users);}}/*** jpaSpecificationExecutor 接口 多條件測(cè)試*/@Testpublic void jpaSpecificationExecutor2() {/*** Specification<Users> 用于封裝條件*/Specification<Users> spec = new Specification<Users>() {/*** Root<Users>:查詢對(duì)象屬性封裝* CriteriaQuery<?> query:瘋長(zhǎng)了我們要執(zhí)行的查詢中各個(gè)部分的信息，select from order* CriteriaBuilder:查詢條件的構(gòu)造器，定義不同查詢條件* @param root* @param query* @param criteriaBuilder* @return*/@Overridepublic Predicate toPredicate(Root<Users> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {/*** where name='zhanga' and age = 20* 參數(shù)2：查詢的指*/List<Predicate> list = new ArrayList<>();list.add(criteriaBuilder.equal(root.get("name"), "zhanga"));list.add(criteriaBuilder.equal(root.get("age"), 22));Predicate[] arr = new Predicate[list.size()];return criteriaBuilder.and(list.toArray(arr));}};List<Users> list = usersRepositorySpecification.findAll(spec);for (Users users : list) {System.out.println(users);}}/*** jpaSpecificationExecutor 接口 多條件測(cè)試2*/@Testpublic void jpaSpecificationExecutor3() {/*** Specification<Users> 用于封裝條件*/Specification<Users> spec = new Specification<Users>() {/*** Root<Users>:查詢對(duì)象屬性封裝* CriteriaQuery<?> query:瘋長(zhǎng)了我們要執(zhí)行的查詢中各個(gè)部分的信息，select from order* CriteriaBuilder:查詢條件的構(gòu)造器，定義不同查詢條件* @param root* @param query* @param cb* @return*/@Overridepublic Predicate toPredicate(Root<Users> root, CriteriaQuery<?> query, CriteriaBuilder cb) {/*** where name='zhanga' and age = 20* 參數(shù)2：查詢的指*/ // List<Predicate> list = new ArrayList<>(); // list.add(criteriaBuilder.equal(root.get("name"), "zhanga")); // list.add(criteriaBuilder.equal(root.get("age"), 22)); // Predicate[] arr = new Predicate[list.size()];//只有and // return cb.and(cb.equal(root.get("name"),"zhanga"),cb.equal(root.get("age"),22));//只有or // return cb.or(cb.equal(root.get("name"),"zhanga"),cb.equal(root.get("age"),22));//and+or//name='zhanga' and age=22 or id =2 and 的優(yōu)先級(jí)高于or 相當(dāng)于//(name='zhanga' and age=22) or id =2return cb.or(cb.equal(root.get("name"), "zhanga"), cb.equal(root.get("age"), 22), cb.equal(root.get("id"), 2));}};//添加排序規(guī)則Sort sort = new Sort(new Sort.Order(Sort.Direction.DESC, "id"));List<Users> list = usersRepositorySpecification.findAll(spec, sort);for (Users users : list) {System.out.println(users);}} }

本文源碼下載：

github地址：
https://github.com/gb-heima/Spring-Boot-Actual-Combat/tree/master/parent/spring-boot-chapter-9

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