<button mat-raised-button class="button-primary button-primary-small" (click)="exportCSV(refName)" disabled="{{!isRefInit}}"><mat-icon color="primary">cloud_download</mat-icon>&nbsp;Export CSV</button>
          <button mat-raised-button class="button-primary button-primary-small" (click)="exportTxt(refName)" disabled="{{!isRefInit}}"><mat-icon color="primary">cloud_download</mat-icon>&nbsp;Export TXT</button>
          <button mat-raised-button class="button-primary button-primary-small" (click)="clearFilter()" disabled="{{!isRefInit}}">
            <mat-icon color="primary">clear</mat-icon>Clear filters
          </button>
          <button mat-raised-button class="button-primary" (click)="export(selectedReferenceTableNames)" [disabled]="tab === 'SQUARE' ? (!isAllCheckboxEnabled && !isSqrRefSelected) : !isRefInit" [style.width.px]="('export.ref.message' | translate).length+7*25">
            <mat-icon color="primary" >swap_horiz</mat-icon>{{'export.ref.message' | translate}}</button>


  exportCSV(refName): void {
    this.referentialsService.downloadReferential(refName, 'csv');
  }

  exportTxt(refName): void {
    this.referentialsService.downloadReferential(refName, 'txt');
  }

  export(selectedReferenceTableNames: string[]): void {
    let title: string;
    if (selectedReferenceTableNames.length > 1) {
      title = `Export referential tables to other environment`;
    } else if (selectedReferenceTableNames.length === 1) {
      title = `${this.translateService.instant('export.ref.message')} : ${selectedReferenceTableNames[0]}`;
    }
    const dialogRef = this.dialog.open(ConfirmationComponent, {
      width: 'auto',
      data: {refNames: selectedReferenceTableNames, refType: this.selectedReferentialItem, title: title }
    });
    dialogRef.afterClosed().subscribe((data) => {
      if (data) {
      }
    });
  }
  
  
  private readonly downloadReferentialEndpoint = '/api/fileService/referential/';
  
    downloadReferential(refName: string, format: string): void {
    window.location.href = `${environment.baseUrl}${this.downloadReferentialEndpoint}${refName}/${format}`;
  }
  
   
 FileManagementController.java 
      @PreAuthorize("hasPermission(returnObject, 'DownloadOutputFile')")
    @GetMapping(value = "/referential/{refName:.+}/{format}", produces = MediaType.APPLICATION_JSON_VALUE)
    public void downloadReferential(@PathVariable String refName, @PathVariable String format,
                                HttpServletResponse response) throws IOException, SQLException, ParseException {
        System.out.println("this is the referential names:: {}"+ refName);
            String fileName = refName+(("csv".equalsIgnoreCase(format))?".csv":".txt");
            response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
            response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename="+fileName);
            refProcessor.writeRefDataToOutputStream(refName, null, response.getOutputStream(), false);
    }
    
    
    RefProcessor.java
    public void writeRefDataToOutputStream(String refName, String[] conditions, OutputStream stream, boolean skipHeader) throws SQLException, ParseException, IOException {
        genericReferentialService.writeRefDataToOutputStream(dataSource, refName, conditions, stream, skipHeader, ';');
    }
    
    GenericReferentialService.java
        public void writeRefDataToOutputStream(DataSource dataSource, String refName, String[] conditions, OutputStream stream, boolean skipHeader, char separator) throws SQLException, ParseException, IOException {
        genericReferentialRepository.writeRefDataToOutputStream(dataSource, refName, conditions, stream, skipHeader, separator);
    }
    
    
    GenericReferentialRepository.java
      void writeRefDataToOutputStream(DataSource dataSource, String refName, String[] conditions, OutputStream stream, boolean skipHeader, char separator) throws SQLException, IOException, ParseException;
      
    JpaGenericReferentialRepository.java
    @Override
    public void writeRefDataToOutputStream(DataSource dataSource, String refName, String[] conditions, OutputStream stream, boolean skipHeader, char separator) throws SQLException, ParseException, IOException {
        StringBuilder builder = new StringBuilder("SELECT * FROM "+ refName );
        if(conditions!=null && conditions.length>0){
            builder.append(((conditions[0]!=null)?WHERE_S+conditions[0]:""));
            for (int i=1; i<conditions.length; i++){
                builder.append(((conditions[i]!=null)?AND_S+conditions[i]:""));
            }
        } else if (refNameService.getProjectionRefs().contains(refName.toUpperCase())) {
            builder = getBuilderForProjectionRefs(dataSource, builder);
        }
        builder.append(String.format(ORDER_BY, ROWID));
        try (PreparedStatement statement = dataSource.getConnection().prepareStatement(builder.toString());
             PrintWriter pw = new PrintWriter(stream, true, StandardCharsets.ISO_8859_1); ResultSet rs = statement.executeQuery()) {
            ResultSetMetaData rsmd = rs.getMetaData();
            int columnCount = rsmd.getColumnCount();
            if(!skipHeader) writeHeader(rsmd, columnCount, pw, separator);
            while (rs.next()) {
                for (int i = 1; i <= columnCount; i++) {
                    Object value = rs.getObject(i);
                    pw.write(value == null ? "" : formatDateColumn(value.toString(), rsmd.getColumnType(i)));
                    if (i != columnCount) {
                        pw.append(separator);
                    }
                }
                pw.println();
            }
        }
    }
    
    
    TarUtils.java
      public static File createZipFile(String parentDir, String output, File... files) throws IOException {
        var fileFullName = CommonFileUtils.buildPath(parentDir, output);
        var outPutFile = new File(fileFullName);
        if (outPutFile.createNewFile()) {
            try (var stream = Files.newOutputStream(outPutFile.toPath());
                 var out = new ZipOutputStream(stream)){
                for (var file: files) {
                    var path = file.toPath();
                    var zipEntry = new ZipEntry(file.getName());
                    out.putNextEntry(zipEntry);
                    Files.copy(path, out);
                    out.closeEntry();
                    out.flush();
                    stream.flush();
                    Files.delete(path);
                }
            }
        }
        return outPutFile;
    }  
    
Expected:

1. Pass a list of selected reference table names (selectedReferenceTableNames) to the exportCSV and exportTxt methods instead of a single refName. from the frontend to backend

2. in backend I want to receive the refNames as String[] eg. ["REF_N001","REF_N013","REF_N011","REF_N015"]

3. If only one reference table ["REF_N001"] is selected by the user, then download the file and should be named (e.g., refName.csv or refName.txt) and download

4. If multiple reference tables ["REF_N001","REF_N013","REF_N011","REF_N015"] are selected by the user, then download the all the files and zip it together and then name it referentials.zip and download

5. Modify the code to handle both single and zip file when multiple

Modify the code as per the above Expected

Can modify the code as per expectation. and reuse the createZipFile method from the TarUtils class to create the ZIP file.   
    
    in exportCSV and exportTxt instead of passing single refName now I want to pass selectedReferenceTableNames, according to this I want to modify the rest of the code such that it works with multiple refName and I should get the download in the zip format. can you please modify the code base as expected
    if the refNames size is one then the particular refName should be displayed e.g refName.csv or refName.txt if the refNames size is more than one then referentials.zip which should should contain all the csv files or txt files

I want to do above logic in GenericReferentialService and reuse the createZipFile to do the zip