1、提交作业添加限制；

2、服务指标；

mec-biz/src/main/java/com/ym/mec/biz/service/impl/StudentServeServiceImpl.java

@@ -123,7 +123,7 @@ public class StudentServeServiceImpl implements StudentServeService {
                     long replyNum = studentHomeworks.stream().filter(e -> YesOrNoEnum.YES.equals(e.getStatus())).count();
                     studentExtracurricularExercisesSituation.setExercisesReplyNum(replyNum>0?1:0);
                     if(replyNum>0){
-                        Date lastSubmitTime = studentHomeworks.stream().max(Comparator.comparing(StudentServeCourseHomeworkDto::getSubmitTime)).get().getSubmitTime();
+                        Date lastSubmitTime = studentHomeworks.stream().filter(e->Objects.nonNull(e.getSubmitTime())).max(Comparator.comparing(StudentServeCourseHomeworkDto::getSubmitTime)).get().getSubmitTime();
                         studentExtracurricularExercisesSituation.setLastSubmitTime(lastSubmitTime);
                     }
                     int exercisesMessageNum=0;
@@ -160,7 +160,7 @@ public class StudentServeServiceImpl implements StudentServeService {
                 long replyNum = studentExercises.stream().filter(e -> e.getStatus()==1).count();
                 studentExtracurricularExercisesSituation.setExercisesReplyNum(replyNum>0?1:0);
                 if(replyNum>0){
-                    Date lastSubmitTime = studentExercises.stream().max(Comparator.comparing(ExtracurricularExercisesReply::getSubmitTime)).get().getSubmitTime();
+                    Date lastSubmitTime = studentExercises.stream().filter(e->Objects.nonNull(e.getSubmitTime())).max(Comparator.comparing(ExtracurricularExercisesReply::getSubmitTime)).get().getSubmitTime();
                     studentExtracurricularExercisesSituation.setLastSubmitTime(lastSubmitTime);
                 }
                 int exercisesMessageNum=0;