一、前言

之前项目在xml中写sql，感觉标签有很多，比较灵活；

最近在写新项目，使用了jpa，只能在java中写sql了，感觉不太灵活，但是也得凑付用。

以下总结下常用入参出参写法。

二、Repository代码样例

@SuppressWarnings("unused")
@Repository
public interface HourRepository extends JpaRepository<Dlhour, Long>, JpaSpecificationExecutor<Dlhour> {@Query(value = "SELECT * " +"FROM dlhour d,bsc_user_t A " +"WHERE A.user_name = d.ename AND A.user_identity = '0' " +"and IF(?1 !='' and ?1 is not null , A.user_name = ?1 ,1=1 )  " +"and IF(?2 !='' and ?2 is not null,A.`NAME` LIKE concat('%', ?2, '%') ,1=1 )  " +"and IF(?3 !='' and ?3 is not null , d.fact_startdate >= ?3 ,1=1 )  " +"and if(COALESCE(?4,NULL) IS NOT NULL,   A.company in  (?4) ,1=1 ) " +"GROUP BY user_id ", countQuery = "SELECT count(*) " +"FROM dlhour d,bsc_user_t A " +"WHERE A.user_name = d.ename AND A.user_identity = '0' " +"and IF(?1 !='' and ?1 is not null , A.user_name = ?1 ,1=1 )  " +"and IF(?2 !='' and ?2 is not null,A.`NAME` LIKE concat('%', ?2, '%') ,1=1 )  " +"and IF(?3 !='' and ?3 is not null , d.fact_startdate >= ?3 ,1=1 )  " +"and if(COALESCE(?4,NULL) IS NOT NULL,   A.company in  (?4) ,1=1 ) " +"GROUP BY user_id ", nativeQuery = true)Page<Map<String, Object>> findClassHour(String user_name, String name, String fact_startdate,  List<String> companys, Pageable pageable);}

说明：
1.这是一个根据条件查询结果列表的接口，有分页，有入参pageable（不用自己手写分页了）
2.Dlhour是javabean，与数据库中的一张表对应，字段一一对应，注意必须有id列。
3.user_name是第一个入参，放入sql中就是等于的条件
4.name是第二个入参，放入sql中可以模糊查询
5.fact_startdate是第三个入参，可以用来查询时间范围，string类型就可以，例如2023-11-06
6.companys是第四个入参，是List<String>类型，放入sql用来查询in条件

三、其余部分代码样例

1.Service层

@Service
public class ClassHourService {private final Logger log = LoggerFactory.getLogger(ClassHourService.class);@Autowiredprivate HourRepository hourRepository;public Page<Map<String, Object>> findClassHour(JSONObject reqJson, Pageable pageable) {List<String> companys = null;String company = reqJson.getString("company");if(company!=null && !"".equals(company)){companys = Arrays.asList(company.split(","));}return hourRepository.findClassHour(reqJson.getString("user_name"), reqJson.getString("name"), reqJson.getString("fact_startdate"), companys, pageable);}
}

说明：
(1)前端传来的参数company，是逗号分隔的，转为List<String>类型的companys，当入参
(2)直接从前端传来的json报文中拿到user_name, name, fact_startdate参数
(3)pageable参数是前端传来的（好像在header里），直接传下去

2.Controller层

@RestController
@RequestMapping("/first")
public class ClassHourResource {private final Logger log = LoggerFactory.getLogger(ClassHourResource.class);@Autowiredprivate ClassHourService classHourService;@GetMapping("/second/findClassHour")public ResponseEntity<List<Map<String,Object>>> findClassHour(@RequestBody JSONObject reqJson, Pageable pageable) {log.debug("REST request to findClassHour: {}", reqJson.toJSONString());Page<Map<String,Object>> page = classHourService.findClassHour(reqJson, pageable);HttpHeaders headers = PaginationUtil.generatePaginationHttpHeaders(page, "/first/second/findClassHour");return ResponseEntity.ok().headers(headers).body(page.getContent());}}

说明：
(1)入参是json请求体reqJson，pageable（前端框架自带了，这个其实是请求url?后的page与size参数决定的）
(2)然后把参数扔到service层，获取返回值
(3)使用PaginationUtil获取了一个响应头headers，里面包含总页数、当前页数等前端框架需要的信息（这些信息在响应header里）
(4)最后把查询到的数据放入响应体（格式可以认为是JsonArray），返回给前端

3.PaginationUtil样例

import org.springframework.data.domain.Page;
import org.springframework.http.HttpHeaders;
import org.springframework.web.util.UriComponentsBuilder;public final class PaginationUtil {private PaginationUtil() {}public static <T> HttpHeaders generatePaginationHttpHeaders(Page<T> page, String baseUrl) {HttpHeaders headers = new HttpHeaders();headers.add("X-Total-Count", Long.toString(page.getTotalElements()));String link = "";if ((page.getNumber() + 1) < page.getTotalPages()) {link = "<" + generateUri(baseUrl, page.getNumber() + 1, page.getSize()) + ">; rel=\"next\",";}// prev linkif ((page.getNumber()) > 0) {link += "<" + generateUri(baseUrl, page.getNumber() - 1, page.getSize()) + ">; rel=\"prev\",";}// last and first linkint lastPage = 0;if (page.getTotalPages() > 0) {lastPage = page.getTotalPages() - 1;}link += "<" + generateUri(baseUrl, lastPage, page.getSize()) + ">; rel=\"last\",";link += "<" + generateUri(baseUrl, 0, page.getSize()) + ">; rel=\"first\"";headers.add(HttpHeaders.LINK, link);return headers;}private static String generateUri(String baseUrl, int page, int size) {return UriComponentsBuilder.fromUriString(baseUrl).queryParam("page", page).queryParam("size", size).toUriString();}
}

说明：
(1)这个方法大概就是把总页数、当前页等信息放入响应头，供前端框架使用
(2)前端框架是react antd框架
(3)对应的这个方法也是后端框架自己封装的，与前端antd对应