Article directory
The query looks like:
where area in (1,2,6,7)
and (price<10
or price between 15 and 20
or price >30)
and (keyword like '%标题%' or keyword like '%简介%')
Scenario description:
area is an area. You can choose
multiple options or
not
. The buildings in Shenzhen and Shanghai are between 15w-30w, and houses above 40w.
Select dynamic query + further fuzzy search.
前端也只给了我们三个字段area,price,keyword
后端技术栈也只是JPA
Solution:
areaId passes a string shaped like "1, 2, 3" and cuts it at the back end. You can also pass a one-dimensional array directly from the front end 以下实例将以"1,2,3"的字符串参数for analysis.
Price passes a two-dimensional array string "[[0,20],[15,20],[30]]". For arrays below xxx, use [0, xxx ], use [xxx] to analyze above xxx.
1. Controller layer
设规定前端发送application/json的POST请求
public Map getCars(@RequestBody Map<String,String> map) throws JsonProcessingException {
String page = map.get("page");
String perPage = map.get("per_page");
String areaId = map.get("area_id");
String keyword = map.get("keyword");
// 类型转化失败将被全局异常处理
int currentPage = page == null || Integer.parseInt(page) <= 0 ? StatusConstants.CURRENT_PAGE : Integer.valueOf(page);
int pageSize = perPage == null || Integer.parseInt(perPage) <= 0 ? StatusConstants.PAGE_SIZE : Integer.valueOf(perPage);
Integer[][] totalPrice = null;
// jack解析二维数组字符串 解析失败将被全局异常处理
if(StringUtils.isNotBlank(map.get("total_price"))){
JsonMapper jsonMapper = new JsonMapper();
totalPrice = jsonMapper.readValue(map.get("total_price"), Integer[][].class);
}
return carsService.getCars(currentPage - 1, pageSize, areaId, totalPrice);
}
2. Service layer
需要在Mapper层继承JpaRepository<Car, Integer>, JpaSpecificationExecutor<Car>
// 封装对地区"1,2,3"解析为集合
private List<Integer> verifyAreaId(String areaId) {
if (StringUtils.isBlank(areaId)) {
return null;
}
List<Integer> areaIds = new ArrayList<>();
String[] split = areaId.split(",");
for (String s : split) {
if (StringUtils.isNumeric(s)) {
areaIds .add(Integer.valueOf(s));
}
}
return areaIds ;
}
// 对获取条件选择的cars
@Override
public Map getCars(Integer page, Integer perPage, String areaId, Integer[][] totalPrice,String keyword) {
// 面向对象 ,反射动态获取排序参数
Sort.TypedSort<Car> typedSort = Sort.sort(Car.class);
Sort descending = typedSort.by(Car::getTotalPrice).descending();
// 获取分页方法
Pageable pageable = PageRequest.of(page, perPage, descending);
Map result = new HashMap();
// 校验有areaId参数
List<Integer> areaIds = verifyAreaId(areaId);
// 拼接查询条件
Specification<Car> queryCondition = (root, query, criteriaBuilder) -> {
List<Predicate> predicateList = new ArrayList<>();
// 拼接areaId查询条件
if (Optional.ofNullable(areaIds).isPresent()) {
predicateList.add(criteriaBuilder.in(root.get("areaId")).value(areaIds));
}
// 拼接totalPrice查询条件
if (Optional.ofNullable(totalPrice).isPresent()) {
ArrayList<Object> objects = new ArrayList<>();
for (Integer[] price : totalPrice) {
switch (price.length) {
case 2 -> {
if (price[0] == 0) {
objects.add(criteriaBuilder.lessThanOrEqualTo(root.get("totalPrice"), price[1]));
} else {
objects.add(criteriaBuilder.between(root.get("totalPrice"), price[0], price[1]));
}
}
case 1 -> objects.add(criteriaBuilder.greaterThanOrEqualTo(root.get("totalPrice"), price[0]));
default -> throw new TotalPriceException("价格区间参数错误");
}
}
// totalPrice查询条件是or的关系
predicateList.add(criteriaBuilder.or(objects.toArray(new Predicate[0])));
}
if(StringUtils.isNotBlank(keyword)){
predicateList.add(criteriaBuilder.or(criteriaBuilder.like(root.get("title"), "%" + keyword + "%"),
criteriaBuilder.like(root.get("detail"), "%" + keyword + "%")));
}
// areaId和totalPrice查询条件是and的关系
return criteriaBuilder.and(predicateList.toArray(new Predicate[0]));
};
// 查询
Page<Car> carPage = carsMapper.findAll(queryCondition, pageable);
result.put("ok", true);
result.put("msg", HttpCodeEnum.SUCCESS.getMsg());
result.put("data", carPage.getContent());
result.put("total", carPage.getTotalElements());
return result;
}
stitching result
where (car0_.area_id in (? , ?))
and car0_.total_price>=0
order by car0_.total_price desc limit ?
where car0_.area_id in (?) order by car0_.total_price desc limit ?
