如何用poi生成导出excel

import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Sheet;

import java.util.List;
import java.util.Map;

/**
 * <p>excel 简单表格 赋值接口<p>
 * @version 1.0
 * @author li_hao
 * @date 2017年1月18日
 */
public interface ColVal {

    void setColVal(List<Map<String, Object>> list, String[] keys, Sheet sheet, CellStyle colValCellStyle);
}

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import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import java.util.List;
import java.util.Map;
import java.util.Objects;

/**
 * <p>excel 简单表格 赋值 实现<p>
 * @version 1.0
 * @author li_hao
 * @date 2017年1月18日
 */
public class CommonColVal implements ColVal {

    /**
     * @param list            数据map
     * @param keys            列值  key
     * @param sheet           {@link Sheet}
     * @param colValCellStyle {@link CellStyle}
     */
    @Override
    public void setColVal(List<Map<String, Object>> list, String[] keys, Sheet sheet, CellStyle colValCellStyle) {
        int rowNum = 1; // 行号
        int i = 0;
        for (; i < list.size(); i++, rowNum++) {
            // 创建行
            Row row = sheet.createRow(rowNum);
            // 获取当前行 数据map
            Map<String, Object> rowValMap = list.get(i);

            // 遍历 key值 给每个列赋值
            for (int j = 0; j < keys.length; j++) {
                Object cellVal = rowValMap.get(keys[j]);

                Cell cell = row.createCell(j);
                cell.setCellValue(Objects.toString(cellVal, ""));
                cell.setCellStyle(colValCellStyle);
            }
        }
    }
}

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import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddress;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.List;
import java.util.Map;

/**
 * <p>导出Excel文档工具类<p>
 * @version 1.0
 * @author li_hao
 * @date 2017年1月18日
 */
public class PoiUtils {

    private static CellStyle buildColValCellStyle(Workbook wb) {
        CellStyle filedValCellStyle = wb.createCellStyle();
        Font f2 = wb.createFont();
        // 创建第二种字体样式（用于值）
        f2.setFontHeightInPoints((short) 10);
        f2.setColor(IndexedColors.BLACK.getIndex());
        // 设置第二种单元格的样式（用于值）
        filedValCellStyle.setFont(f2);
        filedValCellStyle.setBorderLeft(CellStyle.BORDER_THIN);
        filedValCellStyle.setBorderRight(CellStyle.BORDER_THIN);
        filedValCellStyle.setBorderTop(CellStyle.BORDER_THIN);
        filedValCellStyle.setBorderBottom(CellStyle.BORDER_THIN);
        filedValCellStyle.setAlignment(CellStyle.ALIGN_CENTER);
        filedValCellStyle.setVerticalAlignment(CellStyle.VERTICAL_CENTER);
        return filedValCellStyle;
    }

    private static CellStyle buildColNameCellStyle(Workbook wb) {
        // 创建两种单元格格式
        CellStyle filedNameCellStyle = wb.createCellStyle();
        // 创建两种字体
        Font f = wb.createFont();
        // 创建第一种字体样式（用于列名）
        f.setFontHeightInPoints((short) 10);
        f.setColor(IndexedColors.BLACK.getIndex());
        f.setBoldweight(Font.BOLDWEIGHT_BOLD);
        // 设置第一种单元格的样式（用于列名）
        filedNameCellStyle.setFont(f);
        filedNameCellStyle.setBorderLeft(CellStyle.BORDER_THIN);
        filedNameCellStyle.setBorderRight(CellStyle.BORDER_THIN);
        filedNameCellStyle.setBorderTop(CellStyle.BORDER_THIN);
        filedNameCellStyle.setBorderBottom(CellStyle.BORDER_THIN);
        filedNameCellStyle.setAlignment(CellStyle.ALIGN_CENTER);
        return filedNameCellStyle;
    }

    /**
     * 创建excel文档，
     *
     * @param list        数据
     * @param keys        list中map的key数组集合
     * @param columnNames excel的列名
     */
    public static Workbook createSheet(Workbook wb, String sheetName, String titleName, List<Map<String, Object>> list, String[] keys, String columnNames[], ColVal colVal) {

        // 创建第一个sheet（页），并命名
        Sheet sheet = wb.createSheet(sheetName);

        setColLength(keys, sheet);
        CellStyle colNameCellStyle = buildColNameCellStyle(wb);
        CellStyle colValCellStyle = buildColValCellStyle(wb);

        setTitle(titleName, sheet, colNameCellStyle, new CellRangeAddress(0, 0, 0, keys.length - 1));
        setColName(columnNames, sheet, colNameCellStyle, 1);
        colVal.setColVal(list, keys, sheet, colValCellStyle);

        return wb;
    }

    /**
     * 创建excel文档，
     *
     * @param list        数据
     * @param keys        list中map的key数组集合
     * @param columnNames excel的列名
     */
    public static Workbook createSheetNoTitle(Workbook wb, String sheetName, List<Map<String, Object>> list, String[] keys, String columnNames[], ColVal colVal) {

        Sheet sheet = wb.createSheet(sheetName);
        setColLength(keys, sheet);
        CellStyle colNameCellStyle = buildColNameCellStyle(wb);
        CellStyle colValCellStyle = buildColValCellStyle(wb);
        setColName(columnNames, sheet, colNameCellStyle, 0);
        colVal.setColVal(list, keys, sheet, colValCellStyle);

        return wb;
    }

    private static void setTitle(String titleName, Sheet sheet1, CellStyle colNameCellStyle, CellRangeAddress cellRangeAddress) {
        //表头
        Row titleRow = sheet1.createRow(0);
        Cell titleRowCell = titleRow.createCell(0);
        titleRowCell.setCellValue(titleName);
        titleRowCell.setCellStyle(colNameCellStyle);
        sheet1.addMergedRegion(cellRangeAddress);
    }

    private static void setColLength(String[] keys, Sheet sheet1) {
        // 手动设置列宽。第一个参数表示要为第几列设；，第二个参数表示列的宽度，n为列高的像素数。
        for (int i = 0; i < keys.length; i++) {
            sheet1.setColumnWidth((short) i, (short) (35.7 * 150));
        }
    }

    private static void setColName(String[] columnNames, Sheet sheet1, CellStyle cs, int rowNum) {
        // 列名行
        Row row = sheet1.createRow(rowNum);

        //设置列名
        for (int i = 0; i < columnNames.length; i++) {
            Cell cell = row.createCell(i);
            cell.setCellValue(columnNames[i]);
            cell.setCellStyle(cs);
        }
    }

    public static void setResponse(HttpServletResponse response, String fileName, ByteArrayOutputStream os) throws IOException {
        byte[] content = os.toByteArray();
        InputStream is = new ByteArrayInputStream(content);
        // 设置response参数，可以打开下载页面
        response.reset();
        response.setContentType("application/vnd.ms-excel;charset=utf-8");
        response.setHeader("Content-Disposition", "attachment;filename=" + new String((fileName + ".xls").getBytes(), "iso-8859-1"));
        ServletOutputStream out = response.getOutputStream();
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        try {
            bis = new BufferedInputStream(is);
            bos = new BufferedOutputStream(out);
            byte[] buff = new byte[2048];
            int bytesRead;
            // Simple read/write loop.
            while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
                bos.write(buff, 0, bytesRead);
            }
        } catch (final IOException e) {
            throw e;
        } finally {
            if (bis != null)
                bis.close();
            if (bos != null)
                bos.close();
        }
    }

}

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代码示例：