fix bugs

exam-work-api/src/main/java/cn/com/qmth/examcloud/service/examwork/service/ExamStudentService.java

@@ -179,18 +179,20 @@ public class ExamStudentService {
 	}
 
 	private ExamStudent saveStudent(ExamStudent examStudent) {
-		Student student = new Student();
-		student.setIdentityNumber(examStudent.getIdentityNumber());
-		student.setName(examStudent.getName());
-		student.setStudentCode(examStudent.getStudentCode());
-		User user = new User();
-		user.setOrgId(examStudent.getOrgId());
-		user.setEnable(true);
-		user.setType(UserType.STUDENT);
-		user.setRootOrgId(examStudent.getRootOrgId());
-		student.setUser(user);
-		student = studentService.addStudent(student);
-		examStudent.setStudentId(student.getId());
+		if(examStudent.getStudentId() == null){
+			Student student = new Student();
+			student.setIdentityNumber(examStudent.getIdentityNumber());
+			student.setName(examStudent.getName());
+			student.setStudentCode(examStudent.getStudentCode());
+			User user = new User();
+			user.setOrgId(examStudent.getOrgId());
+			user.setEnable(true);
+			user.setType(UserType.STUDENT);
+			user.setRootOrgId(examStudent.getRootOrgId());
+			student.setUser(user);
+			student = studentService.addStudent(student);
+			examStudent.setStudentId(student.getId());
+		}
 		examStudent.setFinished(false);
 		examStudent.setGraduated(false);
 		examStudent.setDegree(false);