java通过poi导出Excel（自动获取对象属性）

骑猪看日落 2022-05-06 04:30 512阅读 0赞

### 虽然可以自己遍历list给Excel赋值添加生成Excel数据，但是缺点明显 ###

*  效率低
 *  如果字段多，写起来十分复杂
 *  灵活性差，每个不同的类要写不同都遍历

## 所有我们需要自动识别实体类导出Excel ##

我们导入jar包  
maven的pom.xml

<dependency>
                <groupId>org.apache.poi</groupId>
                <artifactId>poi-ooxml</artifactId>
                <version>3.14-beta1</version>
            </dependency>
            <dependency>
                <groupId>org.apache.poi</groupId>
                <artifactId>poi-ooxml-schemas</artifactId>
                <version>3.14-beta1</version>
            </dependency>
            <dependency>
                <groupId>org.apache.poi</groupId>
                <artifactId>poi</artifactId>
                <version>3.14-beta1</version>
            </dependency>
            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.2</version>
            </dependency>

### 自动识别实体类导出Excel需要一些工具类 ###

\--------代码搬运工---------  
ExcelBean.java

package top.maniy.entity;
    
    import org.apache.poi.xssf.usermodel.XSSFCellStyle;
    
    public class ExcelBean implements  java.io.Serializable{
    private String headTextName; //列头（标题）名
    private String propertyName; //对应字段名
    private Integer cols; //合并单元格数
    private XSSFCellStyle cellStyle;
    
        public ExcelBean(){
        }
        public ExcelBean(String headTextName, String propertyName){
            this.headTextName = headTextName;
            this.propertyName = propertyName;
        }
    
        public ExcelBean(String headTextName, String propertyName, Integer cols) {
            super();
            this.headTextName = headTextName;
            this.propertyName = propertyName;
            this.cols = cols;
        }
        public String getHeadTextName() {
            return headTextName;
        }
    
        public void setHeadTextName(String headTextName) {
            this.headTextName = headTextName;
        }
    
        public String getPropertyName() {
            return propertyName;
        }
    
        public void setPropertyName(String propertyName) {
            this.propertyName = propertyName;
        }
    
        public Integer getCols() {
            return cols;
        }
    
        public void setCols(Integer cols) {
            this.cols = cols;
        }
    
        public XSSFCellStyle getCellStyle() {
            return cellStyle;
        }
    
        public void setCellStyle(XSSFCellStyle cellStyle) {
            this.cellStyle = cellStyle;
        }
    }

ExcelUtil.java

package top.maniy.util;
    
    import org.apache.http.ParseException;
    import org.apache.http.client.utils.DateUtils;
    import org.apache.poi.hssf.usermodel.HSSFWorkbook;
    import org.apache.poi.ss.usermodel.Cell;
    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.util.CellRangeAddress;
    import org.apache.poi.xssf.usermodel.*;
    import top.maniy.entity.ExcelBean;
    
    import java.beans.IntrospectionException;
    import java.beans.PropertyDescriptor;
    import java.io.InputStream;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.math.BigDecimal;
    import java.text.DecimalFormat;
    import java.text.NumberFormat;
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.Map;
    
    public class ExcelUtil {
        private final static String excel2003L =".xls";    //2003- 版本的excel
        private final static String excel2007U =".xlsx";   //2007+ 版本的excel
        /**
         * Excel导入
         */
        public static  List<List<Object>> getBankListByExcel(InputStream in, String fileName) throws Exception{
            List<List<Object>> list = null;
            //创建Excel工作薄
            Workbook work = getWorkbook(in,fileName);
            if(null == work){
                throw new Exception("创建Excel工作薄为空！");
            }
            Sheet sheet = null;
            Row row = null;
            Cell cell = null;
            list = new ArrayList<List<Object>>();
            //遍历Excel中所有的sheet
            for (int i = 0; i < work.getNumberOfSheets(); i++) {
                sheet = work.getSheetAt(i);
                if(sheet==null){continue;}
                //遍历当前sheet中的所有行
                //包涵头部，所以要小于等于最后一列数,这里也可以在初始值加上头部行数，以便跳过头部
                for (int j = sheet.getFirstRowNum(); j <= sheet.getLastRowNum(); j++) {
                    //读取一行
                    row = sheet.getRow(j);
                    //去掉空行和表头
                    if(row==null||row.getFirstCellNum()==j){continue;}
                    //遍历所有的列
                    List<Object> li = new ArrayList<Object>();
                    for (int y = row.getFirstCellNum(); y < row.getLastCellNum(); y++) {
                        cell = row.getCell(y);
                        li.add(getCellValue(cell));
                    }
                    list.add(li);
                }
            }
            return list;
        }
        /**
         * 描述：根据文件后缀，自适应上传文件的版本
         */
        public static  Workbook getWorkbook(InputStream inStr,String fileName) throws Exception{
            Workbook wb = null;
            String fileType = fileName.substring(fileName.lastIndexOf("."));
            if(excel2003L.equals(fileType)){
                wb = new HSSFWorkbook(inStr);  //2003-
            }else if(excel2007U.equals(fileType)){
                wb = new XSSFWorkbook(inStr);  //2007+
            }else{
                throw new Exception("解析的文件格式有误！");
            }
            return wb;
        }
        /**
         * 描述：对表格中数值进行格式化
         */
        public static  Object getCellValue(Cell cell){
            Object value = null;
            DecimalFormat df = new DecimalFormat("0");  //格式化字符类型的数字
            SimpleDateFormat sdf = new SimpleDateFormat("yyy-MM-dd");  //日期格式化
            DecimalFormat df2 = new DecimalFormat("0.00");  //格式化数字
            switch (cell.getCellType()) {
                case Cell.CELL_TYPE_STRING:
                    value = cell.getRichStringCellValue().getString();
                    break;
                case Cell.CELL_TYPE_NUMERIC:
                    if("General".equals(cell.getCellStyle().getDataFormatString())){
                        value = df.format(cell.getNumericCellValue());
                    }else if("m/d/yy".equals(cell.getCellStyle().getDataFormatString())){
                        value = sdf.format(cell.getDateCellValue());
                    }else{
                        value = df2.format(cell.getNumericCellValue());
                    }
                    break;
                case Cell.CELL_TYPE_BOOLEAN:
                    value = cell.getBooleanCellValue();
                    break;
                case Cell.CELL_TYPE_BLANK:
                    value = "";
                    break;
                default:
                    break;
            }
            return value;
        }
        /**
         * 导入Excel表结束
         * 导出Excel表开始
         * @param sheetName 工作簿名称
         * @param clazz  数据源model类型
         * @param objs   excel标题列以及对应model字段名
         * @param map  标题列行数以及cell字体样式
         */
        public static XSSFWorkbook createExcelFile(Class clazz, List objs, Map<Integer, List<ExcelBean>> map, String sheetName) throws
                IllegalArgumentException,IllegalAccessException,InvocationTargetException,
                ClassNotFoundException, IntrospectionException, ParseException {
            // 创建新的Excel工作簿
            XSSFWorkbook workbook = new XSSFWorkbook();
            // 在Excel工作簿中建一工作表，其名为缺省值, 也可以指定Sheet名称
            XSSFSheet sheet = workbook.createSheet(sheetName);
            // 以下为excel的字体样式以及excel的标题与内容的创建，下面会具体分析;
            createFont(workbook); //字体样式
            createTableHeader(sheet, map); //创建标题（头）
            createTableRows(sheet, map, objs, clazz); //创建内容
            return workbook;
        }
        private static XSSFCellStyle fontStyle;
        private static XSSFCellStyle fontStyle2;
        public static void createFont(XSSFWorkbook workbook) {
            // 表头
            fontStyle = workbook.createCellStyle();
            XSSFFont font1 = workbook.createFont();
            font1.setBoldweight(XSSFFont.BOLDWEIGHT_BOLD);
            font1.setFontName("黑体");
            font1.setFontHeightInPoints((short) 14);// 设置字体大小
            fontStyle.setFont(font1);
            fontStyle.setBorderBottom(XSSFCellStyle.BORDER_THIN); // 下边框
            fontStyle.setBorderLeft(XSSFCellStyle.BORDER_THIN);// 左边框
            fontStyle.setBorderTop(XSSFCellStyle.BORDER_THIN);// 上边框
            fontStyle.setBorderRight(XSSFCellStyle.BORDER_THIN);// 右边框
            fontStyle.setAlignment(XSSFCellStyle.ALIGN_CENTER); // 居中
            // 内容
            fontStyle2=workbook.createCellStyle();
            XSSFFont font2 = workbook.createFont();
            font2.setFontName("宋体");
            font2.setFontHeightInPoints((short) 10);// 设置字体大小
            fontStyle2.setFont(font2);
            fontStyle2.setBorderBottom(XSSFCellStyle.BORDER_THIN); // 下边框
            fontStyle2.setBorderLeft(XSSFCellStyle.BORDER_THIN);// 左边框
            fontStyle2.setBorderTop(XSSFCellStyle.BORDER_THIN);// 上边框
            fontStyle2.setBorderRight(XSSFCellStyle.BORDER_THIN);// 右边框
            fontStyle2.setAlignment(XSSFCellStyle.ALIGN_CENTER); // 居中
        }
        /**
         * 根据ExcelMapping 生成列头（多行列头）
         *
         * @param sheet 工作簿
         * @param map 每行每个单元格对应的列头信息
         */
        public static final void createTableHeader(XSSFSheet sheet, Map<Integer, List<ExcelBean>> map) {
            int startIndex=0;//cell起始位置
            int endIndex=0;//cell终止位置
            for (Map.Entry<Integer, List<ExcelBean>> entry : map.entrySet()) {
                XSSFRow row = sheet.createRow(entry.getKey());
                List<ExcelBean> excels = entry.getValue();
                for (int x = 0; x < excels.size(); x++) {
                    //合并单元格
                    if(excels.get(x).getCols()>1){
                        if(x==0){
                            endIndex+=excels.get(x).getCols()-1;
                            CellRangeAddress range=new CellRangeAddress(0,0,startIndex,endIndex);
                            sheet.addMergedRegion(range);
                            startIndex+=excels.get(x).getCols();
                        }else{
                            endIndex+=excels.get(x).getCols();
                            CellRangeAddress range=new CellRangeAddress(0,0,startIndex,endIndex);
                            sheet.addMergedRegion(range);
                            startIndex+=excels.get(x).getCols();
                        }
                        XSSFCell cell = row.createCell(startIndex-excels.get(x).getCols());
                        cell.setCellValue(excels.get(x).getHeadTextName());// 设置内容
                        if (excels.get(x).getCellStyle() != null) {
                            cell.setCellStyle(excels.get(x).getCellStyle());// 设置格式
                        }
                        cell.setCellStyle(fontStyle);
                    }else{
                        XSSFCell cell = row.createCell(x);
                        cell.setCellValue(excels.get(x).getHeadTextName());// 设置内容
                        if (excels.get(x).getCellStyle() != null) {
                            cell.setCellStyle(excels.get(x).getCellStyle());// 设置格式
                        }
                        cell.setCellStyle(fontStyle);
                    }
                }
            }
        }
        public static void createTableRows(XSSFSheet sheet, Map<Integer, List<ExcelBean>> map, List objs, Class clazz)
                throws IllegalArgumentException, IllegalAccessException, InvocationTargetException, IntrospectionException,
                ClassNotFoundException, ParseException {
            int rowindex = map.size();
            int maxKey = 0;
            List<ExcelBean> ems = new ArrayList<>();
            for (Map.Entry<Integer, List<ExcelBean>> entry : map.entrySet()) {
                if (entry.getKey() > maxKey) {
                    maxKey = entry.getKey();
                }
            }
            ems = map.get(maxKey);
            List<Integer> widths = new ArrayList<Integer>(ems.size());
            for (Object obj : objs) {
                XSSFRow row = sheet.createRow(rowindex);
                for (int i = 0; i < ems.size(); i++) {
                    ExcelBean em = (ExcelBean) ems.get(i);
                    // 获得get方法
                    PropertyDescriptor pd = new PropertyDescriptor(em.getPropertyName(), clazz);
                    Method getMethod = pd.getReadMethod();
                    Object rtn = getMethod.invoke(obj);
                    String value = "";
                    // 如果是日期类型进行转换
                    if (rtn != null) {
                        if (rtn instanceof Date) {
                            value = DateUtils.formatDate((Date)rtn,"yyyy-MM-dd");
                        } else if(rtn instanceof BigDecimal){
                            NumberFormat nf = new DecimalFormat("#,##0.00");
                            value=nf.format((BigDecimal)rtn).toString();
                        } else if((rtn instanceof Integer) && (Integer.valueOf(rtn.toString())<0 )){
                            value="--";
                        }else {
                            value = rtn.toString();
                        }
                    }
                    XSSFCell cell = row.createCell(i);
                    cell.setCellValue(value);
                    cell.setCellType(XSSFCell.CELL_TYPE_STRING);
                    cell.setCellStyle(fontStyle2);
                    // 获得最大列宽
                    int width = value.getBytes().length * 300;
                    // 还未设置，设置当前
                    if (widths.size() <= i) {
                        widths.add(width);
                        continue;
                    }
                    // 比原来大，更新数据
                    if (width > widths.get(i)) {
                        widths.set(i, width);
                    }
                }
                rowindex++;
            }
            // 设置列宽
            for (int index = 0; index < widths.size(); index++) {
                Integer width = widths.get(index);
                width = width < 2500 ? 2500 : width + 300;
                width = width > 10000 ? 10000 + 300 : width + 300;
                sheet.setColumnWidth(index, width);
            }
        }
    }

## 使用这些工具类 ##

userService.java

public XSSFWorkbook exportExcel()throws InvocationTargetException, ClassNotFoundException, IntrospectionException, ParseException, IllegalAccessException ;

userServiceImpl.java

@Override
        public XSSFWorkbook exportExcel() throws InvocationTargetException, ClassNotFoundException, IntrospectionException, ParseException, IllegalAccessException {
            //根据条件查询数据，把数据装载到一个list中
            List<User> list = usermapper.findAllUser();
    
            List<ExcelBean> excel=new ArrayList<>();
            Map<Integer,List<ExcelBean>> map=new LinkedHashMap<>();
            XSSFWorkbook xssfWorkbook=new XSSFWorkbook();
            //设置标题栏
            excel.add(new ExcelBean("人员编号","userId",0));
            excel.add(new ExcelBean("用户名","username",0));
            excel.add(new ExcelBean("密码", "password", 0));
    
            map.put(0, excel);
            String sheetName = "用户列表";
            //调用ExcelUtil的方法
            xssfWorkbook = ExcelUtil.createExcelFile(User.class, list, map, sheetName);
            return xssfWorkbook;
        }

## 在浏览器弹出下载框下载Excel ##

UserController

@RequestMapping(value = "/getExcelByClass")
        @ResponseBody
        public String   export(HttpServletRequest request, HttpServletResponse response) throws ClassNotFoundException, IntrospectionException, IllegalAccessException, ParseException, InvocationTargetException, UnsupportedEncodingException, InvocationTargetException, IntrospectionException {
            boolean flag=true;
    
            //response.setHeader("Pragma", "no-cache");
            //response.setHeader("Cache-Control", "no-cache");
            //response.setDateHeader("Expires", 0);//压缩包
    
    
                XSSFWorkbook workbook = userService.exportExcel();
                OutputStream output;
                response.reset(); //清除buffer缓存
                response.setHeader("Content-Disposition", "attachment;filename=" + new String("用户列表".getBytes("UTF-8"),"ISO-8859-1")+".xls");
                response.setContentType("application/vnd.ms-excel;charset=UTF-8");
                try {
                    output = response.getOutputStream();
                    BufferedOutputStream bufferedOutPut = new BufferedOutputStream(output);
                    bufferedOutPut.flush();
                    workbook.write(bufferedOutPut);
                    bufferedOutPut.close();
                } catch (IOException e) {
                    flag=false;
                    e.printStackTrace();
                }
    
            if(flag)
                return "success";
            else
                return "error";
        }