java使用poi将excel模板写入数据并保存本地的工具类

以下是一个使用POI将Excel模板写入数据并保存本地的工具类示例：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;

public class ExcelWriter {
    private File file;
    private Workbook workbook;

    public ExcelWriter(String filePath) throws IOException {
        file = new File(filePath);
        workbook = WorkbookFactory.create(new FileInputStream(file));
    }

    public void writeData(String[] sheetNames, Map<String, Object[][]> data) throws IOException {
        for (String sheetName : sheetNames) {
            Sheet sheet = workbook.getSheet(sheetName);
            Object[][] sheetData = data.get(sheetName);
            if (sheetData != null) {
                int rowIndex = 0;
                for (Object[] rowData : sheetData) {
                    Row row = sheet.getRow(rowIndex);
                    if (row == null) {
                        row = sheet.createRow(rowIndex);
                    }
                    int columnIndex = 0;
                    for (Object cellData : rowData) {
                        Cell cell = row.getCell(columnIndex);
                        if (cell == null) {
                            cell = row.createCell(columnIndex);
                        }
                        if (cellData != null) {
                            if (cellData instanceof Number) {
                                cell.setCellValue(((Number) cellData).doubleValue());
                            } else if (cellData instanceof String) {
                                cell.setCellValue((String) cellData);
                            } else if (cellData instanceof Boolean) {
                                cell.setCellValue((Boolean) cellData);
                            } else {
                                cell.setCellValue(cellData.toString());
                            }
                        }
                        columnIndex++;
                    }
                    rowIndex++;
                }
            }
        }
    }

    public void save() throws IOException {
        workbook.write(new FileOutputStream(file));
        workbook.close();
    }

    public static void main(String[] args) throws IOException {
        ExcelWriter writer = new ExcelWriter("template.xlsx");
        Map<String, Object[][]> data = new HashMap<String, Object[][]>();
        data.put("Sheet1", new Object[][] { { "A1", "B1", "C1" }, { "A2", "B2", "C2" } });
        data.put("Sheet2", new Object[][] { { "X1", "Y1", "Z1" }, { "X2", "Y2", "Z2" } });
        writer.writeData(new String[] { "Sheet1", "Sheet2" }, data);
        writer.save();
    }
}

使用示例：

1. 创建Excel文件"template.xlsx"，在Sheet1和Sheet2中分别添加3列数据；
2. 在Java中使用ExcelWriter类读取"template.xlsx"文件；
3. 调用writeData方法向Sheet1和Sheet2中写入新数据；
4. 调用save方法保存更新后的Excel文件。

注意：ExcelWriter类中的写入数据方法是覆盖式写入，即会清空原有数据，再写入新数据。如果需要追加数据，需要修改方法实现。