JAVA源码分享：基于Apache POI，将List<T>内封装的实体类信息写出到磁盘Excel文件（20170905）

因公司项目需要，临时写的小程序。未优化，结构简单。

与上一版（http://blog.csdn.net/qw3670/article/details/73277226）相比的改进：

修改方法为静态方法，使用时无需初始化ToExcel类。

具体用法见上一版说明。

package tools;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Map.Entry;import java.util.regex.Pattern;import org.apache.poi.hssf.usermodel.HSSFCellStyle;import org.apache.poi.hssf.usermodel.HSSFDataFormat;import org.apache.poi.hssf.usermodel.HSSFRow;import org.apache.poi.hssf.usermodel.HSSFSheet;import org.apache.poi.hssf.usermodel.HSSFWorkbook;import org.apache.poi.ss.usermodel.Cell;/** * 写出到Excel文件. * @author AL *  */public class ToExcel {/** * 匹配数字(非科学计数法). */private static final Pattern general_num=Pattern.compile("^-{0,1}[0-9]+\\.{0,1}[0-9]*$");/** * 匹配数字(科学计数法). */private static final Pattern notation_num=Pattern.compile("^-{0,1}[0-9]+\\.{0,1}[0-9]*E{1}-{0,1}[0-9]+$");/** * 逗号（英文输入状态）. */private static final String comma =",";/** * 等号（英文输入状态）. */private static final String equal_sign ="=";/** * 写出内容到Excel. * map：key为Excel中每个分页的名称、List为分页的内容； * fileName：最终输出的文件名，包含路径。 * @throws WriteExcelFailedException *  */public static<T> void toExcel(Map<String,List<T>> map,String fileName) throws WriteExcelFailedException {//新建文件输出流及Excel表格缓存区FileOutputStream out=null;HSSFWorkbook excel = null;try {out=new FileOutputStream(fileName+".xls");excel = new HSSFWorkbook();} catch (FileNotFoundException e) {throw new WriteExcelFailedException("未知的异常",e);}//此对象用于设置单元格格式为数字格式并保留小数点后两位，备用HSSFCellStyle cellStyle = excel.createCellStyle();cellStyle.setDataFormat(HSSFDataFormat.getBuiltinFormat("0.00"));//若map为空，则重构一个map，装入一个空白键值对if(map==null || map.isEmpty()){map=new HashMap<>();map.put("空", null);}//遍历键值对，将表格名称和表格内容传递给下一层，用于写出for(Entry<String, List<T>> entry : map.entrySet()){//向Excel（缓存区）内填充内容writeWorkbook(entry.getValue(),entry.getKey(),excel,cellStyle);}//写出到磁盘文件writeToDisk(out, excel);}/** * 向Excel（缓存区）内填充内容. * @param result * @param sheetName * @param excel * @param cellStyle  *  */private static<T> void writeWorkbook(List<T> result, String sheetName, HSSFWorkbook excel, HSSFCellStyle cellStyle) {if(sheetName==null  || "".equals(sheetName)){//若sheetName为空，则填充“空”sheetName="空";}HSSFSheet sheet = excel.createSheet(sheetName);if (result == null || result.isEmpty()) {// 若集合为空，则写出“空”字符sheet.createRow(0).createCell(0).setCellValue("空");return;}//按照“,”将集合内元素toString的字符串切割成数组String[] temp = result.get(0).toString().split(comma);HSSFRow row = sheet.createRow(0);//获取此sheet表格的第一行int times=temp.length;for (int t = 0; t < times; t++) {//遍历数组，用于构造表头row.createCell(t).setCellValue(temp[t].substring(0, temp[t].indexOf(equal_sign)));//只取“=”之前的字符}//遍历集合，填充表格内容int size=result.size();for (int i = 1; i <= size; i++) {row = sheet.createRow(i);String[] infos=result.get(i - 1).toString().split(comma);//将toString返回的字符串按","切割成数组int round=infos.length;for (int j = 0; j < round; j++) {//只取“=”之后的字符String info =infos[j].substring(infos[j].indexOf(equal_sign) + 1, infos[j].length()).trim();//获取单元格Cell cell=row.createCell(j);//判断待输入的内容是否是数字if (general_num.matcher(info).matches() || notation_num.matcher(info).matches()) {cell.setCellStyle(cellStyle);cell.setCellValue(Double.parseDouble(info));}else{cell.setCellValue(info);}}}}/** *  写出到磁盘文件. * @param out * @param excel * */private static void writeToDisk(FileOutputStream out, HSSFWorkbook excel) {try {excel.write(out);if(out!=null){//关闭流out.close();}} catch (IOException e) {e.printStackTrace();}}}/** * 异常 * @author AL * */class WriteExcelFailedException extends Exception {private static final long serialVersionUID = 1L;public WriteExcelFailedException() {super();}public WriteExcelFailedException(String message, Throwable cause, boolean enableSuppression,boolean writableStackTrace) {super(message, cause, enableSuppression, writableStackTrace);}public WriteExcelFailedException(String message, Throwable cause) {super(message, cause);}public WriteExcelFailedException(String message) {super(message);}public WriteExcelFailedException(Throwable cause) {super(cause);}}