使用 Apache POI 基于 csv 工作表更新 Excel 工作表值

Question

我还是 Java 新手。我对 java 语法有一点问题。 我的程序应该执行以下过程：

1) 它需要一个 csv 文件作为输入。

2) 它需要一个 excel 文件作为输入。

3) 它应该遍历写入日期的两个文件的第一列。

4) 通过添加 csv 表中的信息来更新 excel 文件并保存其更改。

我有一个https://onedrive.live.com/?cid=24b4fceb4f4e4098&id=24B4FCEB4F4E4098%213018&authkey=%21AKKzaZsJ5pkd5NE

我有两个输入示例以及结果 excel 表的外观。

两个输入文件：

导出-csv-input.csv

export-excel-input.xlsx

更新后的 excel 文件应如下所示：

export-excel-output.xlsx

我的 Java 代码还没有：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.Reader;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class CsvToExcelConverter {

  public static final String SAMPLE_XLSX_FILE_PATH = 
 "C:/Users/blawand/Desktop/CSV_to_Excel/export-excel-test.xlsx";
  public static final String SAMPLE_CSV_FILE_PATH = 
"C:/Users/blawand/Desktop/CSV_to_Excel/export-csv-test.csv";
  public static List<String> dates_csv = new ArrayList<>();
  public static List<String> dates_excel = new ArrayList<>();

  public static void main(String[] args) throws IOException, 
InvalidFormatException {

    try (Reader reader = 
Files.newBufferedReader(Paths.get(SAMPLE_CSV_FILE_PATH));
        CSVParser csvParser = new CSVParser(reader, CSVFormat.DEFAULT);) 
{

      for (CSVRecord csvRecord : csvParser) {
        // Accessing Values by Column Index
         String name = csvRecord.get(0);
        dates_csv.add(name);
      }
      dates_csv.remove(0);
    }

    FileInputStream fsIP = new FileInputStream(new 
File(SAMPLE_XLSX_FILE_PATH));

    /*
     * ================================================================== 
Iterating over all the
     * rows and columns in a Sheet (Multiple ways)
     * ==================================================================
     */

    // Getting the Sheet at index zero
    XSSFWorkbook workbook = new XSSFWorkbook(fsIP);

    XSSFSheet sheet = workbook.getSheetAt(0);

    // Get the Cell at index 2 from the above row
    // Cell cell1 = sheet.getRow(1).getCell(0);
    // for (int i = 0; i < dates_excel.size(); i++) {
    // XSSFRow rowtest = sheet.createRow((short) i + 1);
    // rowtest.createCell(0).setCellValue(dates_csv.get(i));
    //
    // }

    // cell1.setCellValue(dates_csv.get(0));
    // Create a DataFormatter to format and get each cell's value as 
String
    DataFormatter dataFormatter = new DataFormatter();

    for (int rowIndex = 1; rowIndex <= sheet.getLastRowNum(); rowIndex++) 
{
      Row row = sheet.getRow(rowIndex);
      if (row != null) {
        Cell cell = row.getCell(0); // getColumn(0)
        if (cell != null) {
          // Found column and there is value in the cell.
          // String cellValueMaybeNull = cell.getStringCellValue();
          String cellValueMaybeNull = 
dataFormatter.formatCellValue(cell);

      // String to number set
      dates_excel.add(cellValueMaybeNull);

    }
  }
}

System.out.println(dates_csv);
System.out.println(dates_csv.size());
System.out.println(dates_excel);
System.out.println(dates_excel.size());

while (dates_excel == dates_excel) {

  System.out.println("Yes");
  break;
}
fsIP.close();
FileOutputStream output_file = new FileOutputStream(new 
File(SAMPLE_XLSX_FILE_PATH));
workbook.write(output_file);
output_file.close();

  }
}

我已经阅读了这两个文件，但在更新 excel 文件并将项目名称添加到正确日期时遇到问题。如果同一日期在 csv 表中被写入两次或多次。

您还想知道哪些信息？

我会感谢每一个帮助或建议！

Answer 1

我有一个例子给你，主要由代码 cmets 解释。尽管如此，代码基本上做了以下事情：

在构造函数中获取 xlsx 和 csv 文件的文件路径。

更新时，它首先将 csv 文件的内容读入 Map，其中 LocalDate 为键，List<String> 为值。
然后它遍历工作簿的行，跳过标题行并将第一列中的日期与Map<LocalDate, List<String>> 的键进行比较。如果映射包含该键，它会开始检查该行中的单元格的当前值并将它们保存在一个列表中，以便以后不写它们。
然后它开始将值写入具有关键日期的行的单元格中。

我希望这会有所帮助。

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class CsvXlsxUpdater {

    private static final DateTimeFormatter DATE_TIME_FORMATTER_CSV = DateTimeFormatter.ofPattern("dd.MM.yyyy");

    private Path csvFilePath;
    private Path xlsxFilePath;
    private XSSFWorkbook workbook;
    private XSSFSheet sheet;
    private Map<LocalDate, List<String>> csvContent = new TreeMap<LocalDate, List<String>>();
    private ZoneId zoneId = ZoneId.systemDefault();

    public CsvXlsxUpdater(String pathToCsvFile, String pathToXlsxFile) {
        csvFilePath = Paths.get(pathToCsvFile);
        xlsxFilePath = Paths.get(pathToXlsxFile);
    }

    /**
     * Reads the content of the csv file into the corresponding class variable,
     * which is a {@link TreeMap} that has a {@link LocalDate} as key and a 
     * {@link List<String>} as values.
     */
    private void readCsvContent() {
        List<String> csvLines;

        try {
            csvLines = Files.readAllLines(csvFilePath);

            for (int i = 1; i < csvLines.size(); i++) {
                String line = csvLines.get(i);
                String[] splitValues = line.split(",");

                if (splitValues.length > 1) {
                    List<String> lineValues = Arrays.asList(splitValues);
                    List<String> projects = getProjectValuesFrom(lineValues);
                    LocalDate localDate = LocalDate.parse(lineValues.get(0), DATE_TIME_FORMATTER_CSV);
                    if (csvContent.containsKey(localDate)) {
                        projects.forEach((String project) -> {
                            List<String> csvProjects = csvContent.get(localDate);
                            if (!csvProjects.contains(project)) {
                                csvProjects.add(project);
                            }
                        });
                    } else {
                        csvContent.put(localDate, projects);
                    }
                } else {
                    LocalDate localDate = LocalDate.parse(splitValues[0], DATE_TIME_FORMATTER_CSV);
                    csvContent.put(localDate, new ArrayList<String>());
                }
            }
        } catch (IOException e) {
            System.err.println("CANNOT FIND OR READ CSV FILE: " + e.getMessage());
            e.printStackTrace();
        } catch (UnsupportedOperationException e) {
            System.err.println("UNSUPPORTED OPERATION: " + e.getMessage());
            e.printStackTrace();
        }

    }

    /**
     * Gets the corresponding {@link LocalDate} from a given (and deprecated)
     * {@link Date}
     * 
     * @param date the deprecated {@link Date} object
     * @return the corresponding {@link LocalDate}
     */
    private LocalDate parseLocalDateFrom(Date date) {
        Instant instantDate = date.toInstant();
        return instantDate.atZone(zoneId).toLocalDate();
    }

    /**
     * Takes a list of read values from the csv file and returns a list containing
     * all the values of the given list <strong>except from the first
     * element</strong>, which is a {@link String} representation of a date and
     * should be treated differently in this context.
     * 
     * @param values the original list of {@link String}s
     * @return another list without the first element of the given list
     */
    private List<String> getProjectValuesFrom(List<String> values) {
        List<String> projectValues = new ArrayList<String>();

        for (int i = 1; i < values.size(); i++) {
            String value = values.get(i);
            if (!value.equals("")) {
                projectValues.add(value);
            }
        }

        return projectValues;
    }

    /**
     * Updates the workbook with the values read from the csv file
     */
    public void updateWorkbook() {
        readCsvContent();
        try {
            FileInputStream fis = new FileInputStream(xlsxFilePath.toAbsolutePath().toString());
            workbook = new XSSFWorkbook(fis);
            sheet = workbook.getSheetAt(0);
            
            // iterate over the rows
            Iterator<Row> rowIterator = sheet.rowIterator();
            
            while (rowIterator.hasNext()) {
                XSSFRow row = (XSSFRow) rowIterator.next();
                
                if (row.getRowNum() == 0) {
                    // skip this or set updated headers
                } else {
                    // check if the csvContent contains the value of cell(0)
                    LocalDate dateKey = parseLocalDateFrom(row.getCell(0).getDateCellValue()); 
                    if (csvContent.containsKey(dateKey)) {
                        // if yes, get list-value of the key
                        List<String> values = csvContent.get(dateKey);
                        
                        // check if there are values
                        if (values != null) {
                            if (values.size() > 0) {
                                // if there are, then go checking the cell values
                                List<String> projectsInXlsx = new ArrayList<String>();
                                Iterator<Cell> cellIterator = row.cellIterator();
                                int lastColumnIndex = 1;
                                
                                // go through all cells with a value except from the first one
                                while (cellIterator.hasNext()) {
                                    Cell cell = cellIterator.next();
                                    
                                    // skip the first column as it contains the date
                                    if (cell.getColumnIndex() != 0) {
                                        lastColumnIndex = cell.getColumnIndex();
                                        System.out.println("Accessing cell in column " + lastColumnIndex);
                                        // if there is a cell with a value
                                        if (cell.getStringCellValue() != null) {
                                            if (!cell.getStringCellValue().equals("")) {
                                                // check if the value in the cell is also in the csv values
                                                if (values.contains(cell.getStringCellValue())) {
                                                    projectsInXlsx.add(cell.getStringCellValue());
                                                    lastColumnIndex++;
                                                }
                                            }
                                        }
                                    }
                                }
                                
                                // now go through the values of the csv file
                                int offset = 0; // cell column offset for more than one entry per date
                                for (String value : values) {
                                    if (!projectsInXlsx.contains(value)) {
                                        // create a cell after the last one with a value
                                        row.createCell(lastColumnIndex + offset).setCellValue(value);
                                        offset++;
                                    }
                                }
                            }
                        }
                    }
                }
            }
            
            fis.close();
        
            FileOutputStream fileOutputStream = new FileOutputStream(xlsxFilePath.toAbsolutePath().toString());
            workbook.write(fileOutputStream);
            fileOutputStream.flush();
            fileOutputStream.close();
            workbook.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

在main 方法中，您只需调用构造函数，将文件路径作为Strings 传递，然后调用updateWorkbook() 方法，因为它首先在内部读取csv。

例子：

public class CsvXlsxMain {

    private static final String CSV_FILE_PATH = "S:\\ome\\example\\path\\to\\csv-input.csv";
    private static final String XLSX_FILE_PATH = "S:\\ome\\example\\path\\to\\excel-input.xlsx";
    
    public static void main(String[] args) {
        CsvXlsxUpdater cxu = new CsvXlsxUpdater(CSV_FILE_PATH, XLSX_FILE_PATH);
        cxu.updateWorkbook();
    }
}

请记住，此代码未经过全面测试，将来交替资源可能会出现问题 如果需要，请使用各种符合您要求的 xlsx 和 csv 输入对其进行测试。

我没有使用任何库来解析 csv 文件！

我希望这对你有一点帮助……