Get Apache Poi Palette

PoiController.kt

import org.apache.poi.ss.usermodel.FillPatternType
import org.apache.poi.ss.usermodel.IndexedColors
import org.apache.poi.xssf.usermodel.XSSFWorkbook
import org.springframework.http.HttpHeaders
import org.springframework.http.MediaType
import org.springframework.http.ResponseEntity
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController
import java.io.ByteArrayOutputStream

@RestController
class PoiController {
    
    @GetMapping("/palette")
        fun getPoiPalette(): ResponseEntity<ByteArray> {
        val workbook = XSSFWorkbook()
        val sheet = workbook.createSheet("PALETTE")
        IndexedColors.entries.forEachIndexed { index, color ->
            sheet.createRow(index).apply {
                createCell(0).apply {
                    setCellValue(color.name)
                    cellStyle = workbook.createCellStyle().apply {
                        fillForegroundColor = color.index
                        fillPattern = FillPatternType.SOLID_FOREGROUND
                    }
                }
                createCell(1).apply { setCellValue("    ") }
                createCell(2).apply {
                    setCellValue(color.name)
                    cellStyle = workbook.createCellStyle().apply {
                        setFont(sheet.workbook.createFont().apply { bold = true; this.color = color.index })
                    }
                }
            }
        }
        val out = ByteArrayOutputStream()
        workbook.use { it.write(out) }
        val fileName = "poi_palette.xlsx"
        val result = out.toByteArray()
        return ResponseEntity.ok()
            .contentType(MediaType.APPLICATION_OCTET_STREAM)
            .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"$fileName\"")
            .body(result)
    }
}