ADD file via upload

AttendanceService.java

@@ -0,0 +1,53 @@
+package com.example.classroomattendance.service;
+
+import com.example.classroomattendance.model.Student;
+import com.example.classroomattendance.repository.StudentRepository;
+import org.apache.poi.ss.usermodel.*;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.*;
+
+@Service
+public class AttendanceService {
+    @Autowired
+    private StudentRepository studentRepository;
+
+    public List<Student> getAllStudents() {
+        return studentRepository.findAll();
+    }
+
+    public void addPoints(Long studentId, double points) {
+        Optional<Student> student = studentRepository.findById(studentId);
+        student.ifPresent(s -> {
+            s.setPoints(s.getPoints() + points);
+            studentRepository.save(s);
+        });
+    }
+
+    public Student pickRandomStudent() {
+        List<Student> students = getAllStudents();
+        Collections.shuffle(students, new Random(System.nanoTime()));
+        return students.get(0);
+    }
+
+    public void loadStudentsFromExcel(InputStream inputStream) throws IOException {
+        List<Student> students = new ArrayList<>();
+        try (Workbook workbook = new XSSFWorkbook(inputStream)) {
+            Sheet sheet = workbook.getSheetAt(0);
+            for (Row row : sheet) {
+                if (row.getRowNum() == 0) {
+                    continue;
+                }
+                String name = row.getCell(0).getStringCellValue();
+                String studentId = row.getCell(1).getStringCellValue();
+                double points = row.getCell(2).getNumericCellValue();
+                students.add(new Student(name, studentId, points));
+            }
+        }
+        studentRepository.saveAll(students);
+    }
+}