feat: 학생회비 납부자 엑셀파일 다운로드 기능 구현

src/main/kotlin/site/billilge/api/backend/domain/payer/controller/AdminPayerController.kt

@@ -1,5 +1,8 @@
 package site.billilge.api.backend.domain.payer.controller
 
+import org.springframework.core.io.InputStreamResource
+import org.springframework.http.ContentDisposition
+import org.springframework.http.HttpHeaders
 import org.springframework.http.ResponseEntity
 import org.springframework.web.bind.annotation.*
 import site.billilge.api.backend.domain.payer.dto.request.PayerDeleteRequest
@@ -9,6 +12,8 @@ import site.billilge.api.backend.domain.payer.service.PayerService
 import site.billilge.api.backend.global.annotation.OnlyAdmin
 import site.billilge.api.backend.global.dto.PageableCondition
 import site.billilge.api.backend.global.dto.SearchCondition
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
 
 @RestController
 @RequestMapping("/admin/members/payers")
@@ -35,4 +40,20 @@ class AdminPayerController(
         payerService.deletePayers(request)
         return ResponseEntity.noContent().build()
     }
+
+    @GetMapping("/excel")
+    fun createPayerExcel(): ResponseEntity<InputStreamResource> {
+        val excel = payerService.createPayerExcel()
+        val currentDate = LocalDate.now()
+        val dateFormatter = DateTimeFormatter.ofPattern("yyyyMMdd")
+        val headers = HttpHeaders().apply {
+            contentDisposition = ContentDisposition.builder("attachment")
+                .filename("kmusw_payers_${dateFormatter.format(currentDate)}.xlsx")
+                .build()
+        }
+
+        return ResponseEntity.ok()
+            .headers(headers)
+            .body(InputStreamResource((excel)))
+    }
 }

src/main/kotlin/site/billilge/api/backend/domain/payer/repository/PayerRepository.kt

@@ -15,4 +15,6 @@ interface PayerRepository : JpaRepository<Payer, Long?> {
 
     @Query("SELECT p FROM Payer p WHERE p.name LIKE CONCAT('%', :name, '%')")
     fun findAllByNameContaining(@Param("name") name: String, pageable: Pageable): Page<Payer>
+
+    fun findAllByEnrollmentYear(enrollmentYear: String): List<Payer>
 }

src/main/kotlin/site/billilge/api/backend/domain/payer/service/PayerService.kt

@@ -14,12 +14,19 @@ import site.billilge.api.backend.domain.payer.entity.Payer
 import site.billilge.api.backend.domain.payer.repository.PayerRepository
 import site.billilge.api.backend.global.dto.PageableCondition
 import site.billilge.api.backend.global.dto.SearchCondition
+import site.billilge.api.backend.global.utils.ExcelGenerator
+import site.billilge.api.backend.global.utils.ExcelRow
+import java.io.ByteArrayInputStream
+import java.time.Year
 
 @Service
 @Transactional(readOnly = true)
 class PayerService(
     private val payerRepository: PayerRepository,
-    private val memberRepository: MemberRepository
+
+    private val memberRepository: MemberRepository,
+
+    private val excelGenerator: ExcelGenerator
 ) {
     fun isPayer(name: String, studentId: String): Boolean {
         val enrollmentYear = studentId.substring(0, 4)
@@ -71,6 +78,7 @@ class PayerService(
 
     @Transactional
     fun addPayers(request: PayerRequest) {
+        val newPayers = mutableListOf<Payer>()
         request.payers.forEach { payerItem ->
             val name = payerItem.name
             val studentId = payerItem.studentId
@@ -87,18 +95,19 @@ class PayerService(
                     this.registered = registered
                 }
 
-                payerRepository.save(payer)
+                newPayers.add(payer)
             }
 
             registeredMember?.isFeePaid = true
         }
+
+        payerRepository.saveAll(newPayers)
     }
 
     @Transactional
     fun deletePayers(request: PayerDeleteRequest) {
         val payerStudentIds = payerRepository.findAllByIds(request.payerIds)
             .mapNotNull { it.studentId }
-            .toList()
 
         memberRepository.findAllByStudentIds(payerStudentIds)
             .forEach { member ->
@@ -107,4 +116,21 @@ class PayerService(
 
         payerRepository.deleteAllById(request.payerIds)
     }
+
+    fun createPayerExcel(): ByteArrayInputStream {
+        val startYear = 2015
+        val currentYear = Year.now().value
+        val headerTitles = arrayOf("이름", "학번")
+        val sheetData = mutableMapOf<String, Pair<Array<String>, List<ExcelRow>>>()
+
+        for (year in startYear..currentYear) {
+            val yearText = "$year"
+            val payersByYearExcelRow = payerRepository.findAllByEnrollmentYear(yearText)
+                .map { payer -> ExcelRow(payer.name, payer.studentId ?: "${yearText}XXXX") }
+
+            sheetData.put(yearText, headerTitles to payersByYearExcelRow)
+        }
+
+        return excelGenerator.generateByMultipleSheets(sheetData)
+    }
 }

src/main/kotlin/site/billilge/api/backend/global/config/AsyncConfig.kt

@@ -0,0 +1,9 @@
+package site.billilge.api.backend.global.config
+
+import org.springframework.context.annotation.Configuration
+import org.springframework.scheduling.annotation.EnableAsync
+
+@EnableAsync
+@Configuration
+class AsyncConfig {
+}

src/main/kotlin/site/billilge/api/backend/global/utils/ExcelGenerator.kt

@@ -0,0 +1,63 @@
+package site.billilge.api.backend.global.utils
+
+import org.apache.poi.ss.usermodel.IndexedColors
+import org.apache.poi.xssf.streaming.SXSSFSheet
+import org.apache.poi.xssf.streaming.SXSSFWorkbook
+import org.springframework.stereotype.Component
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+
+private const val HEADER_ROW = 0
+
+@Component
+class ExcelGenerator {
+
+    fun generateByMultipleSheets(
+        sheetData: Map<String, Pair<Array<String>, List<ExcelRow>>>
+    ): ByteArrayInputStream {
+        val workbook = SXSSFWorkbook()
+
+        sheetData.forEach { (sheetName, sheetContent) ->
+            val (headerTitles, rows) = sheetContent
+            val sheet = workbook.createSheet(sheetName)
+            styleHeaders(workbook, sheet, headerTitles)
+            fillData(sheet, rows, headerTitles.size)
+        }
+
+        val out = ByteArrayOutputStream()
+        workbook.write(out)
+        workbook.close()
+
+        return ByteArrayInputStream(out.toByteArray())
+    }
+
+    private fun styleHeaders(workbook: SXSSFWorkbook, sheet: SXSSFSheet, headerTitles: Array<String>) {
+        val headerFont = workbook.createFont()
+        headerFont.bold = true
+
+        val headerCellStyle = workbook.createCellStyle()
+        headerCellStyle.setFont(headerFont)
+        headerCellStyle.fillForegroundColor = IndexedColors.GREY_25_PERCENT.index
+        headerCellStyle.fillPattern = org.apache.poi.ss.usermodel.FillPatternType.SOLID_FOREGROUND
+
+        val headerRow = sheet.createRow(HEADER_ROW)
+        headerTitles.forEachIndexed { col, title ->
+            val cell = headerRow.createCell(col)
+            cell.setCellValue(title)
+            cell.cellStyle = headerCellStyle
+        }
+    }
+
+    private fun fillData(sheet: SXSSFSheet, rows: List<ExcelRow>, columnSize: Int) {
+        sheet.trackAllColumnsForAutoSizing()
+
+        rows.forEachIndexed { index, excelRow ->
+            val row = sheet.createRow(index + 1)
+            excelRow.data.forEachIndexed { propertyIndex, property ->
+                row.createCell(propertyIndex).setCellValue(property)
+            }
+        }
+
+        repeat(columnSize) { col -> sheet.autoSizeColumn(col) }
+    }
+}

src/main/kotlin/site/billilge/api/backend/global/utils/ExcelRow.kt

@@ -0,0 +1,7 @@
+package site.billilge.api.backend.global.utils
+
+data class ExcelRow(
+    val data: List<String>
+) {
+    constructor(vararg data: String) : this(data.toList())
+}