update

mec-student/src/main/java/com/ym/mec/student/controller/CourseController.java

@@ -57,8 +57,10 @@ public class CourseController extends BaseController {
         }
         if(groupId.startsWith("mg")){
             return succeed(musicGroupService.get(groupId.substring(2)));
+        }else if(groupId.startsWith("cg")){
+            return succeed(classGroupService.get(Integer.parseInt(groupId.substring(2))));
         }
-        return succeed(classGroupService.get(Integer.parseInt(groupId.substring(2))));
+        return failed("群编号不存在");
     }
 
     @ApiOperation(value = "分页获取学员购买记录")