Angular and Spring Boot Excel Export / Download

In .html file declared a button to download the excel file

<div class="col-md-2">
     <p-button label="Extract & Download Excel" (onClick)="exportCampaign($event)" [disabled]="isShow" id="btnXlsRpt"></p-button>
</div>

exportCampaign($event) {
    $event.stopPropagation();
    $event.preventDefault();
    this.blockedDocument = true;
    this.d = new Date();
    this.year = this.d.getFullYear();
    this.month = this.d.getMonth() + 1;
    this.day = this.d.getDate();
    this.d.getUTCFullYear();
    
   var result= this.mainService.exportCampaignData(this.obj.cmpNameToSearch);
   let fileName="Campaign-"+this.obj.cmpNameToSearch+"_"+this.day + "_" + this.month + "_" + this.year +".xlsx";
   result.subscribe(
    (success: any) => {
      var blob = new Blob([success._body], { type: 'application/vnd.ms-excel' });

      if (window.navigator && window.navigator.msSaveOrOpenBlob) {
        window.navigator.msSaveOrOpenBlob(blob, fileName);
        this.blockedDocument = false;
      } else {
        var a = document.createElement('a');
        a.href = URL.createObjectURL(blob);
        a.download = fileName;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        this.blockedDocument = false;
      }
    },
    err => {
      alert("Error while downloading. File Not Found on the Server");
      this.blockedDocument = false;
    }
  );
}

		<dependency>
			<groupId>org.apache.poi</groupId>
			<artifactId>poi</artifactId>
			<version>4.0.1</version>
		</dependency>
		
		<dependency>
		    <groupId>org.apache.poi</groupId>
		    <artifactId>poi-ooxml</artifactId>
		    <version>4.0.1</version>
		</dependency>

@RequestMapping(value = "/exportExcel", method = RequestMethod.POST)
@ResponseBody
public ResponseEntity<?> exportExcel(HttpServletRequest request, HttpServletResponse response, @RequestBody String campaignName) throws Exception {
		
	XSSFWorkbook workbook = null;
	byte[] contentReturn=null;
	/* Here I got the object structure (pulling it from DAO layer) that I want to be export as part of Excel. */
	vehicleLastSeenByCampaignReport.setCvsSummary(cvsSummary);
	try{
		/* Logic to Export Excel */
		LocalDateTime localDate = LocalDateTime.now();
		String fileName = "CampaignID-" + campaignName + "-" + localDate.toString() + ".xlsx";
		response.setHeader("Content-Disposition", "attachment; filename=" + fileName);
				
		OutputStream out;
workbook = (XSSFWorkbook) exportToFileService.exportToExcel(vehicleLastSeenByCampaignReport);
		out = response.getOutputStream();
		workbook.write(out);
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		workbook.write(baos);
		contentReturn = baos.toByteArray();
		/* Export Excel logic end */
			
		} catch (Exception ecx) {
			VehicleLastSeenByCampaignReport vehicleCampaignReport = new VehicleLastSeenByCampaignReport();
			vehicleCampaignReport.setErrorMessage("Campaign Not Found");
			return new ResponseEntity<byte[]>(null, null, HttpStatus.BAD_REQUEST);
		}finally {
			if (null != workbook) {
				try {
					workbook.close();
				} catch (IOException eio) {
					logger.error("Error Occurred while exporting to XLS ", eio);
				}
			}
		}
		
		HttpHeaders headers = new HttpHeaders();
		headers.setContentType(MediaType.parseMediaType("application/vnd.ms-excel"));
		return new ResponseEntity<byte[]>(contentReturn, headers, HttpStatus.OK);
	}

 public Object exportToExcel(VehicleLastSeenByCampaignReport vehicleLastSeenByCampaignReport) {
		String[] columns = setUpExcelColumns(CVSConstants.EXPORT_DATA_CMP);
		Workbook workbook = CVSUtils.writeExcelFile(vehicleLastSeenByCampaignReport, columns, summaryArray);
		return workbook;
}

public static Workbook writeExcelFile(VehicleLastSeenByCampaignReport vehicleLastSeenByCampaignReport, String[] columns, String[] summaryColumns) {

		Workbook workbook = new XSSFWorkbook();
		int rowNum = 0;
		// Create a Font for styling header cells
		Font headerFont = setHeaderFont(workbook);

		// Create a CellStyle with the font
		CellStyle headerCellStyle = setHeaderCellStyle(workbook, headerFont);
		
		// Create a CellStyle for CampaignSummary mian object with Grey Color
		CellStyle styleGrey = workbook.createCellStyle();
		styleGrey.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
		styleGrey.setFillPattern(FillPatternType.SOLID_FOREGROUND); 
		
		Sheet cmpSummarySheet = workbook.createSheet(CVSConstants.CMP_SUMMARY_SHEET);
		Sheet cmpDetailsSheet = workbook.createSheet(CVSConstants.CMP_DETAILS_SHEET);
		
		Row headerRowcmpSummary = cmpSummarySheet.createRow(0);
		Row headerRowCmpDetails = cmpDetailsSheet.createRow(0);
		
		applyHeaderCellStyle(Arrays.copyOfRange(summaryColumns, 0, (summaryColumns.length)), headerCellStyle, headerRowcmpSummary);
		applyHeaderCellStyle(Arrays.copyOfRange(columns, 0, (columns.length) ), headerCellStyle, headerRowCmpDetails);
		
		//Create the 'cmp summary sheet'
		defineCmpSummary(vehicleLastSeenByCampaignReport, rowNum, cmpSummarySheet, summaryColumns);
		
		//Create the 'cmp details sheet'
		defineCmpDetails(vehicleLastSeenByCampaignReport, rowNum, cmpDetailsSheet, columns, styleGrey);
		
		return workbook;
		
	}
	
	private static void defineCmpSummary(VehicleLastSeenByCampaignReport vehicleLastSeenByCampaignReport, int rowNum, Sheet cmpSummarySheet, String[] summaryCols) {
		Row vehDetailsRow = cmpSummarySheet.createRow(++rowNum);
		CVSSummary cvsSummary = vehicleLastSeenByCampaignReport.getCvsSummary();
		int columnNum = 0;
		
		vehDetailsRow.createCell(columnNum).setCellValue(cvsSummary.getDomain());
		vehDetailsRow.createCell(++columnNum).setCellValue(cvsSummary.getSearchQuery());
		vehDetailsRow.createCell(++columnNum).setCellValue(cvsSummary.getTotalCampaigns());
		vehDetailsRow.createCell(++columnNum).setCellValue(cvsSummary.getCampaignsValidated());		
		vehDetailsRow.createCell(++columnNum).setCellValue(cvsSummary.getCampaignsSkipped());
		
		for (int i = 0; i < summaryCols.length; i++) {
			cmpSummarySheet.autoSizeColumn(i);
		}
	}