java sql查询如何选择没有参数的所有数据

Question

嗨，最近我一直在研究REST API。我在想，如果没有参数，我怎么才能得到所有的数据。我只能通过categoryId获得数据，如下所示。http：//..../categorys？categoryID=2数据被选择并显示如下。

{
  "items": [
  {
  "id": 2,
  "name": "music",
  "count": 20
  }   
 ]
}

{
  "items": [
      {
        "id": 1,
        "name": "movie",
        "count": 10
      },
      {
        "id": 2,
        "name": "music",
        "count": 20
      },
      {
        "id": 3,
        "name": "book",
        "count": 16
      }    
   ]
}

SELECT_CATEGORYS = "SELECT category.id as id, category.name as name, count(*) as count FROM product inner join category where product.category_id = category.id group by category.id, category.name;"

@RestController
@RequestMapping(path="/categorys")
public class CategoryApiController {
@Autowired
ReservationService reservationService;

@GetMapping
public Map<String, Object> categorys(@RequestParam(name="categoryId", required=false, defaultValue="0") int categoryId) {
    
    List<Categorys> list = reservationService.getCategorys(categoryId);
    Map<String, Object> map = new HashMap<>();
    map.put("item", list);
    
    return map;
  }
}

Answer 1

查询

 SELECT_CATEGORYS = "SELECT category.id as id, category.name as name, count(*) as count FROM product inner join category group by category.id, category.name;"

控制器

@RestController
    @RequestMapping(path="/categorys")
    public class CategoryApiController {
    @Autowired
    ReservationService reservationService;
    @GetMapping
    public Map<String,List<Category>> categorys() {
        List<Categorys> list = reservationService.getCategories();
        Map<String, Object> map = new HashMap<>();
        map.put("item", list);
        return map;
      }
    }