SpringDataJPA -06- specification的基本使用

目录

ORMHibernate，JPA和SpringDataJpaJPA入门案列JPA的API介绍getOne和findOne的比较JPQL的基本使用specification的基本使用 ★example的基本使用 多表设计 表之间的划分 分析步骤 多表设计(一对多) 多表设计(一对多) 对象导航查询

specification的使用

 Specification是一个函数式接口，需要实现toPredicate(Root root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder)方法

root：查询的根对象（查询的任何属性都可以从根对象中获取）CriteriaQuery：顶层查询对象，自定义查询方式（了解：一般不用）CriteriaBuilder：查询的构造器，封装了很多的查询条件

单参数查询

@Test public void testSpecificationOneParam(){ Specification<Customer> specification=(root,query,cb)->{ //获取比较属性 Path<Object> custName = root.get("custName"); //构建查询条件 Predicate predicate = cb.equal(custName, "飞飞飞"); return predicate; }; List<Customer> customers = this.customerRepository.findAll(specification); customers.forEach((customer -> System.out.println(customer))); }

多参数查询

@Test public void testSpecificationMoreParam(){ Specification<Customer> specification=(root, query, criteriaBuilder) -> { //获取比较属性 Path<Object> custName = root.get("custName"); Path<Object> custIndustry = root.get("custIndustry"); //构造条件查询 Predicate preName = criteriaBuilder.equal(custName, "飞飞飞"); Predicate preIndy = criteriaBuilder.equal(custIndustry, "娱乐"); //与相连 Predicate predicate = criteriaBuilder.and(preName, preIndy); return predicate; }; List<Customer> customers = this.customerRepository.findAll(specification); customers.forEach((customer)-> System.out.println(customer)); }

模糊查询

@Test public void testSpecificationLike(){ Specification<Customer> specification=(root, query, criteriaBuilder) -> { //获取比较属性 Path<Object> custName = root.get("custName"); //构建查询条件 Predicate predicate = criteriaBuilder.like(custName.as(String.class), "%飞__"); return predicate; }; List<Customer> customers = this.customerRepository.findAll(specification); customers.forEach(customer -> System.out.println(customer)); }

分页查询

@Test public void testSpecificationPage(){ //每页数目 int row=5; //当前页 int page=0; //添加查询条件 Specification<Customer> specification=(root, query, criteriaBuilder) -> { //获取比较属性 Path<Object> custName = root.get("custName"); //构建查询条件 Predicate predicate = criteriaBuilder.like(custName.as(String.class), "%飞__"); return predicate; }; //排序 // Sort sort=Sort.by(Sort.Direction.ASC,"custId"); //分页条件 Pageable pageable=PageRequest.of(page,row,Sort.Direction.ASC,"custId"); //分页查询 Page<Customer> cpage = this.customerRepository.findAll(pageable); //获取数据集合 List<Customer> customers = cpage.getContent(); //获取总页数 int totalPages = cpage.getTotalPages(); //获取总条数 long totalElements = cpage.getTotalElements(); System.out.println("数据总页数:"+totalPages); System.out.println("数据总条数:"+totalElements); customers.forEach(customer -> System.out.println(customer)); }

输出