使用POI导出Excel自适应列宽的实现

使用POI导出Excel时，涉及到如何自适应列宽的问题。方法如下

/** 
     * 下载excel文件,内容使用MAP存放 
     *  
     * @param response 
     * @param headName 
     * @param tableHead 
     * @param tableBody 
     * @throws IOException 
     */  
    public static void downloadExcelMap(HttpServletResponse response, String headName, List<String> tableHead,  
            List<Map<Object, Object>> tableBody) throws IOException {  
        headName=StringUtils.replaceAllSpecial(headName);  
        // 1:创建一个workbook  
        HSSFWorkbook workbook = new HSSFWorkbook();  
  
        // 创建样式  
        HSSFCellStyle style = workbook.createCellStyle();  
        Font font = workbook.createFont();  
        font.setBoldweight(Font.BOLDWEIGHT_BOLD); // 粗体  
        style.setFont(font);  
        style.setAlignment(HSSFCellStyle.ALIGN_CENTER); // 水平居中  
        style.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER); // 垂直居中  
        style.setBorderTop((short) 1);  
        style.setBorderBottom((short) 1);  
        style.setBorderLeft((short) 1);  
        style.setBorderRight((short) 1);  
        style.setWrapText(true);  
  
        // 设置合计样式  
        HSSFCellStyle style1 = workbook.createCellStyle();  
        style1.setAlignment(HSSFCellStyle.ALIGN_CENTER); // 水平居中  
        style1.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER); // 垂直居中  
        style1.setBorderTop((short) 1);  
        style1.setBorderBottom((short) 1);  
        style1.setBorderLeft((short) 1);  
        style1.setBorderRight((short) 1);  
        style.setWrapText(true);  
  
        HSSFSheet sheet = (HSSFSheet) workbook.createSheet(headName);  
        // 2：合并单元格，表头。并设置值  
        CellRangeAddress cra = new CellRangeAddress(0, 0, 0, tableHead.size() - 1);  
        sheet.addMergedRegion(cra);  
        HSSFRow row = sheet.createRow(0);  
        HSSFCell tableName = row.createCell(0);  
        tableName.setCellStyle(style);  
        tableName.setCellValue(headName);  
  
        //存储最大列宽  
        Map<Integer,Integer> maxWidth = new HashMap<Integer,Integer>();  
          
        // 3：设置表head  
        HSSFRow row1 = sheet.createRow(1);  
        for (int i = 0; i < tableHead.size(); i++) {  
            Cell createCell = row1.createCell(i);  
            createCell.setCellValue(tableHead.get(i));  
            createCell.setCellStyle(style);  
            maxWidth.put(i,createCell.getStringCellValue().getBytes().length  * 256 + 200);  
        }  
        // 4：表格内容  
        for (int i = 0; i < tableBody.size(); i++) {  
            HSSFRow rows = sheet.createRow(i + 2);  
            int j = 0;  
            for (Map.Entry<Object, Object> entry : tableBody.get(i).entrySet()) {  
                HSSFCell createCell = rows.createCell(j);  
                if(PropertyUtil.objectNotEmpty(entry.getValue())){  
                    createCell.setCellValue(entry.getValue().toString());  
                }else{  
                    createCell.setCellValue("");  
                }  
                int length = createCell.getStringCellValue().getBytes().length  * 256 + 200;  
                //这里把宽度最大限制到15000  
                if (length>15000){  
                    length = 15000;  
                }  
                maxWidth.put(j,Math.max(length,maxWidth.get(j)));  
                j++;  
                createCell.setCellStyle(style1);  
            }  
        }  
          
        // 列宽自适应  
        for (int i = 0; i < tableHead.size(); i++) {  
            sheet.setColumnWidth(i,maxWidth.get(i));  
        }  
  
        // 5：设置头  
        response.setHeader("Content-disposition",  
                "attachment; filename=" + new String(headName.getBytes("GB2312"), "ISO8859-1") + ".xls");  
        // 6：设置头类型  
        response.setContentType("application/vnd.ms-excel");  
          
        // 7：写出  
        OutputStream toClient = response.getOutputStream();  
        workbook.write(toClient);  
        toClient.flush();  
        toClient.close();  
  
    }  

注意：以上代码有15000的限制，原因是Excel限制最大宽度为15000。所以，在这里我们除了这个宽度处理外，还需要设置单元格自动换行

style.setWrapText(true);  

http://pigga.iteye.com/blog/2430931