springData学习（五）JpaRepository和JpaSpecificationExecutor接口学习

1.JpaRepository接口中的主要方式有：

其实很以前的方法一样，我们主要学习一下findAll（Sort sort） 方法

@Test public void testFindAllSort() { Order order = new Order(Sort.Direction.DESC, "age"); Sort sort = new Sort(order); List<Student> sList = studentJpa.findAll(sort); sList.forEach(System.out::println); }

2.JpaSpecificationExecutor接口

不属于Repository体系，实现一组 JPA Criteria 查询相关的方法 Specification：封装 JPA Criteria 查询条件。通常使用匿名内部类的方式来创建该接口的对象

在上文的基础上，在继承JpaSpecificationExecutor接口。

其中path的包为：javax.persistence.criteria.Path;

public interface StudentJpa extends JpaRepository<Student, Integer>, JpaSpecificationExecutor<Student>{ } 测试类： /** * 1 分页 * 2 排序 * 3 条件查询 */ @Test public void testQuery() { Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id"); Sort sort = new Sort(order); Pageable pageable = new PageRequest(0, 4,sort);//分页条件 Specification<Student> specification = new Specification<Student>() { @Override public Predicate toPredicate(Root<Student> root, CriteriaQuery<?> query, CriteriaBuilder cb) { //root中包含了Student Student包含了score Path path = root.get("score"); Predicate predicate = cb.gt(path, 5); return predicate; } }; Page<Student> page = studentJpa.findAll(specification, pageable); System.out.println("查询的总页数"+page.getTotalPages()); System.out.println("查询的总记录数"+page.getTotalElements()); System.out.println("查询的当前第几页"+page.getNumber()+1); System.out.println("查询的当前页面的集合"+page.getContent()); System.out.println("查询的当前页面的记录数"+page.getNumberOfElements()); }

如果我们想同时搜索多个条件时：

比如搜索年龄19岁且分数为90的人员信息

@Test public void testQuery() { Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id"); Sort sort = new Sort(order); Pageable pageable = new PageRequest(0, 4,sort);//分页条件 Specification<Student> specification = new Specification<Student>() { @Override public Predicate toPredicate(Root<Student> root, CriteriaQuery<?> query, CriteriaBuilder cb) { //root中包含了Student Student包含了score Path path = root.get("score"); Path path1 = root.get("age"); Predicate p1 = cb.equal(path, 90); Predicate p2 = cb.equal(path1, 18); return cb.and(p1, p2); } }; Page<Student> page = studentJpa.findAll(specification, pageable); System.out.println("查询的总页数"+page.getTotalPages()); System.out.println("查询的总记录数"+page.getTotalElements()); System.out.println("查询的当前第几页"+page.getNumber()+1); System.out.println("查询的当前页面的集合"+page.getContent()); System.out.println("查询的当前页面的记录数"+page.getNumberOfElements()); }