工作中导出Excel是最常见的功能，如何快速实现导出？这里介绍一下我封装好的导出Excel工具，仅需要配置一下Excel的列并提供需要导出的数据即可导出Excel文件。

1.引入依赖

 <dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>3.17</version>
</dependency>
  

2. ExcelSheetSettingEnum

定义Excel的一些配置信息

 public enum ExcelSheetSettingEnum {
    REPORT_TEST("report_test", "Excel文件名称", new String[]{"Sheet名称1", "Sheet名称2"}, new String[]{"标题1", "标题2"}, new String[][]{
            {"字段名称A", "字段名称B", "字段名称C", "字段名称D"},
            {"字段名称A", "字段名称B", "字段名称C", "字段名称D"}
    }),
    REPORT_TEST2("report_test2", "Excel文件名称", new String[]{"标题1", "标题2"}),
    REPORT_TEST3("report_test3", "Excel文件名称")
    ;

    ExcelSheetSettingEnum(String code, String filename) {
        this.code = code;
        this.filename = filename;
    }

    ExcelSheetSettingEnum(String code, String filename, String[] titles) {
        this.code = code;
        this.filename = filename;
        this.titles = titles;
    }

    ExcelSheetSettingEnum(String code, String filename, String[] sheetnames, String[] titles, String[][] headers) {
        this.code = code;
        this.filename = filename;
        this.sheetnames = sheetnames;
        this.titles = titles;
        this.headers = headers;
    }

    /** 代码标识(必选) */
    private String code;

    /** 代码标识(必选) */
    private String filename;

    /** Sheet名称(可选) */
    private String[] sheetnames;

    /** Sheet标题(可选) */
    private String[] titles;

    /** 表头名称(可选) */
    private String[][] headers;


    // Getter & Setter
}
  

3. ExcelView

定义Excel视图，继承自AbstractXlsxView或者AbstractXlsView, 需要实现一个abstract方法buildExcelDocument用于创建Sheet，构造Excel数据。

继承关系如下：

 /**
 * Excel视图
 *
 * 支持多个Sheet, Sheet名称、标题和表头不是必须的
 * AbstractPdfView和AbstractXlsxView原理大致相同
 * 
 * @author mengday zhang
 */
public class ExcelView extends AbstractXlsxView {

    @Override
    protected void buildExcelDocument( Map <String,  Object > map,  workbook  workbook, HttpServletRequest request, HttpServletResponse response) throws Exception {
        ExcelSheetSettingEnum setting = (ExcelSheetSettingEnum) map.get("ExcelSheetSetting");

        // 设置文件名称
        String filename = setting.getFilename();
        filename = new String(filename.getBytes("UTF-8"),"ISO8859-1");
        response.setHeader(HttpHeaders.CONTENT_DISPOSITION,"attachment;filename=" + filename + ".xlsx");

        List<List<List<String>>> sheets = (List<List<List<String>>>) map.get("data");
        for (int i = 0; i < sheets.size(); i++) {
            // 创建sheet
            String[] sheetNames = setting.getSheetnames();
            String sheetName = "Sheet" + (i + 1);
            if (sheetNames != null && sheetNames.length > 0) {
                sheetName = sheetNames[i];
            }
            Sheet sheet = workbook.createSheet(sheetName);

            // 如果标题不为空的话，将表格的第一行作为标题行，并合并第一行的N个单元格
            int index = 0;
            String[] titles = setting.getTitles();
            String[][] headerss = setting.getHeaders();
            List<List<String>> rowsForTable = sheets.get(i);
            if (titles != null && titles.length > 0) {
                // 合并标题单元格 下标从0开始 起始行号，终止行号， 起始列号，终止列号
                CellRangeAddress region = new CellRangeAddress(0, 0, 0, rowsForTable.get(0).size() - 1);
                sheet.addMergedRegion(region);

                Row titleRow = sheet.createRow(index++);
                Cell titleCell = titleRow.createCell(0);
                CellStyle cellStyle = workbook.createCellStyle();
                cellStyle.setAlignment(HorizontalAlignment.CENTER);
                 font  font = workbook.createFont();
                font.setFontName("黑体");
                font.setBold(true);
                font.setFontHeightInPoints((short) 15);
                cellStyle.setFont(font);
                titleCell.setCellStyle(cellStyle);
                titleCell.setCellValue(titles[i]);
            }

            // 创建表头行
            if (headerss != null && headerss.length > 0) {
                Row headerRow = sheet.createRow(index++);
                String[] headers = headerss[i];
                for(int j = 0; j < headers.length; j++) {
                    headerRow.createCell(j).setCellValue(headers[j]);
                }
            }

            // 创建数据行
            AtomicInteger rowIndex = new AtomicInteger(index);
            rowsForTable. forEach (rowList -> {
                Row row = sheet.createRow(rowIndex.getAndIncrement());
                AtomicInteger x = new AtomicInteger();
                rowList.forEach(cell ->
                        row.createCell(x.getAndIncrement()).setCellValue(cell)
                );
            });
        }
    }
}
  

4.controller

mvc方法中方法的返回值是ModelAndView, 当代码执行new ModelAndView(excelView, map)时会执行ExcelView#buildExcelDocument的方法

 @RestController
@RequestMapping("/excel")
public class ExcelController {

    @RequestMapping("/export")
    public ModelAndView export(){

        List<List<String>> sheet1 = Arrays.asList(
            Arrays.asList("1", "11", "111", "1111"),
            Arrays.asList("2", "22", "222", "2222"),
            Arrays.asList("3", "33", "333", "3333")
        );

        List<List<String>> sheet2 = Arrays.asList(
            Arrays.asList("4", "44", "444", "4444"),
            Arrays.asList("5", "55", "555", "5555"),
            Arrays.asList("6", "66", "666", "6666")
        );
        List<List<List<String>>> sheets = Arrays.asList(sheet1, sheet2);

        Map<String, Object> map = new HashMap<>();
        map.put("ExcelSheetSetting", ExcelSheetSettingEnum.REPORT_TEST2);
        map.put("data", sheets);

        ExcelView excelView = new ExcelView();
        return new ModelAndView(excelView, map);
    }
}    
  

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