需求::
- 有一个List<Map<String.Object>>,存储了某年某月的数据,
数据是根据用户查询条件进行显示的;所以查询的数据是动态的; - 需按月份统计每个年月数据出现的次数,并且按照月份排序;
- 统计周期不超过一年(前端页面控制);
分析::
后端给前端返回值:不能用对象返回,因为数据是动态的,key是不固定的;
可以使用:List<Map<String,Object>>返回;Map中key为年月;value为统计次数;
Demo案例:
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;public class day06 {public static void main(String[] args) {List<Map<String,Object>> list = new ArrayList<>();Map<String,Object> map1 = new HashMap<>();map1.put("month","2023年02月");Map<String,Object> map2 = new HashMap<>();map2.put("month","2023年05月");Map<String,Object> map3 = new HashMap<>();map3.put("month","2023年04月");Map<String,Object> map4 = new HashMap<>();map4.put("month","2023年02月");Map<String,Object> map5 = new HashMap<>();map5.put("month","2023年01月");list.add(map1);list.add(map2);list.add(map3);list.add(map4);list.add(map5);String[] auditMonthArr = {"01","02","03","04","05","06","07","08","09","10","11","12"};int[] count = new int[auditMonthArr.length];String[] yearArr = new String[auditMonthArr.length];for (int i = 0; i < list.size(); i++) {String auditMonth = String.valueOf(list.get(i).get("month")).trim();String auditMonth2 = auditMonth.substring(auditMonth.indexOf("年")+1,auditMonth.indexOf("月"));for (int j = 0; j < auditMonthArr.length; j++) {if(auditMonth2.equals(auditMonthArr[j].trim())){count[j] = count[j] + 1;yearArr[j] = auditMonth;}}}List<Map<String,Object>> listResult = new ArrayList<>();// 按照1月到12月动态展示数据;for (int i = 0; i < auditMonthArr.length; i++) {Map<String,Object> map = new HashMap<>();String title = yearArr[i];int value = count[i];if(!String.valueOf(value).equals("0")){map.put("title",title);map.put("value",value);listResult.add(map);}} for (int i = 0; i < listResult.size(); i++) {listResult.get(i).put("sortValue",i+1);}System.out.println("listResult:"+listResult);}
}
测试输出:
listResult:
listResult:[{sortValue=1, title=2023年01月, value=1}, {sortValue=2, title=2023年02月, value=2}, {sortValue=3, title=2023年04月, value=1}, {sortValue=4, title=2023年05月, value=1}]
案例二:
需求:前端根据后端的返回数据:画趋势图;
- X轴是动态的,有对应月份数据则展示;
- X轴 按照1-12月排序(没月份则跳过);
// Controllerpublic Result getTrendData(HttpServletRequest request,@RequestBody String param) {try {Map<String, Object> paramMap = JsonUtils.readValue(param, Map.class);return Result.success().result(questionListService.getTrendData(request,paramMap));} catch (Exception e) {log.error("QuestionListController getTrendData is error===:" + e.getMessage(), e);return Result.failure("统计失败");}}// Service List<Map<String,Object>> getTrendData(HttpServletRequest request,Map<String, Object> paramMap);// ServiceImpl @Overridepublic List<Map<String,Object>> getTrendData(HttpServletRequest request, Map<String, Object> paramMap) {List<Map<String,Object>> list = getCountData(request,paramMap); // 封装统计查询的数据(与数据库交互)List<Map<String,Object>> listResult = new ArrayList<>();String[] auditMonthArr = {"01","02","03","04","05","06","07","08","09","10","11","12"};int[] monDataArr = new int[auditMonthArr.length];String[] yearArr = new String[auditMonthArr.length];for (int i = 0; i < list.size(); i++) {String auditMonth = String.valueOf(list.get(i).get("auditMonth"));String mon = auditMonth.substring(auditMonth.indexOf("年")+1,auditMonth.lastIndexOf("月"));for (int j = 0; j < auditMonthArr.length; j++) {if(mon.equals(auditMonthArr[j])){monDataArr[j] = monDataArr[j] + 1;yearArr[j] = auditMonth;}}}// 按照1月到12月动态展示数据;for (int i = 0; i < auditMonthArr.length; i++) {Map<String,Object> map = new HashMap<>();String title = yearArr[i];int value = monDataArr[i];// 该判断很重要(仔细品)if(!String.valueOf(value).equals("0")){map.put("title",title);map.put("value",value);listResult.add(map);}}return listResult;}
Postman接口测试: