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);
