利用Try-with-resources（TWR）读取Excel文件

使用原因： 当我们在读取字节流时，将取到的字节流写入到文件中，首先我们要打开流，用完之后将流关闭，在关闭的操作过程中很容易产生错误，比如，我们在进行try，catch的时候，即使遇到异常，但是并做不了什么。

TWR的优势： 改变了语法，减少了错误发生的可能行。

Java7资源管理语法

try (OutputStream out = new FileOutputStream(file);     InputStream is = url.openStream() ) {  byte[] buf = new byte[4096];  int  len;  while ((len = is.read(buf)) > 0) {    out.write(buf, 0, len);  }}

具体实现代码

import com.yinglian.java.core.entities.ResultMessage;import lombok.extern.apachecommons.CommonsLog;import org.apache.poi.hssf.usermodel.HSSFDateUtil;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.xssf.usermodel.XSSFWorkbook;import org.springframework.util.StringUtils;import java.io.*;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.regex.Matcher;import java.util.regex.Pattern;/** * @author gmh * @ClassName: ExcelUtil * @Description: Ｅxcel表格数据获取工具类 * @date 2017年3月31日 下午6:18:08 */@CommonsLogpublic class ExcelUtil {    private String filPath;    private String sheetName;    private List<String> headlist;    private List<Map<String, String>> maplist;    public ExcelUtil(String filPath) {        this.filPath = filPath;    }    /**     * 获取excel数据信息     *     * @return     */    public List<Map<String, String>> getMaplist() {        return maplist;    }    /**     * 获取表头信息     *     * @return     */    public List<String> getHead() {        return headlist;    }    /**     * 获取excel所有的数据信息集合     *     * @return　 返回excel中的所有数据信息集合     */    public List<Map<String, String>> getContents() {        log.info("开始读取Ｅxcel表中数据信息");        ArrayList<ArrayList<String>> rows = null;        Workbook rwb = null;        Sheet sheet = null;        File file = new File(this.filPath);        try (FileInputStream stream = new FileInputStream(file)) {            if (checkFileFormat(filPath)) {                rwb = new HSSFWorkbook(stream);            } else {                rwb = new XSSFWorkbook(stream);            }            sheet = rwb.getSheetAt(0);            sheetName = sheet.getSheetName();            int totalRows = sheet.getPhysicalNumberOfRows();            if (totalRows > 0 && sheet.getRow(0) != null) {                int totalCells = sheet.getRow(0).getPhysicalNumberOfCells();                rows = readExcel(sheet, totalRows, totalCells);                if (rows.size() == 0) {                    log.info("excel表格中没有数据信息");                    return null;                }                headlist = getPerRowInfo(0, totalCells, sheet);                //log.info("开始将Ｅxcel表中处理后信息进行封装到Map中");                maplist = new ArrayList<>();                //循环行，然后封装进map                for (int k = 0; k < rows.size(); k++) {                    //log.info("开始封装第" + (k + 1) + "行．．．．．．．．．．．．．．．．．．．．");                    HashMap<String, String> map = PerRowInfoToMap(k, headlist, rows);                    maplist.add(map);                }            }        } catch (FileNotFoundException e) {            log.error("excel文件不存在", e);        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                file.delete();                log.info("读取Ｅxcel表中数据信息完成");            } catch (Exception e) {                log.error("本地文件删除出错",e);            }        }        return maplist;    }    /**     * 写入excel文件     * @param localPath     *          本地存储地址     * @param faildatalist     *          失败数据集合     */    public ResultMessage<String> writeExcel(String localPath, List<Map<String, String>> faildatalist) {        ResultMessage<String> resultMessage = new ResultMessage<>();        log.info(String.format("开始向文件:%s写入数据",localPath));        Row row = null;        Workbook rwb = null;        int cellnum = 0;        try (FileOutputStream outputStream = new FileOutputStream(localPath)) {            rwb = new XSSFWorkbook();            Sheet sheet = rwb.createSheet(sheetName);            //表格列数            cellnum = headlist.size();            //填入表头            row = sheet.createRow(0);            for (int i = 0; i < cellnum; i++) {                Cell cell = row.createCell(i);                cell.setCellValue(headlist.get(i));            }            //填入内容            for (int i = 0; i < faildatalist.size(); i++) {                row = sheet.createRow(i + 1);                for (int j = 0; j < cellnum; j++) {                    Cell cell = row.createCell(j);                    cell.setCellValue(faildatalist.get(i).get(headlist.get(j)));                }            }            rwb.write(outputStream);            log.info("写入数据结束");            resultMessage.setSuccess(true);        } catch (Exception e) {            resultMessage.setSuccess(false);            resultMessage.setMessage("保存错误数据为Excel文件时出错" + e.getMessage());            log.error("保存错误数据为Excel文件时出错", e);        }        return resultMessage;    }        /**         * 获得excel的Sheet表         *         * @param filePath excel文件的地址         *         * @return 返回判断结果         */    private boolean checkFileFormat(String filePath) {        boolean is = false;        Pattern p = Pattern.compile("\\.(xls)$");        Matcher m = p.matcher(filePath);        if (m.find()) {            is = true;        }        return is;    }    /**     * 获取sheet表中的每一行信息集合     *     * @param rownum excel表格信息的行数     * @param cells  excel表格总共的列数     * @param sheet  excel第一张Sheet表     * @return 返回每行数据信息集合     */    private ArrayList<String> getPerRowInfo(int rownum, int cells, Sheet sheet) {        ArrayList<String> rowlist = null;        int emptynum = 0;        try {            rowlist = new ArrayList<>();            for (int j = 0; j < cells; j++) {                String rightTypeCell = "";                Cell cell = sheet.getRow(rownum).getCell(j);                rightTypeCell = getRightTypeCell(cell);                if (StringUtils.isEmpty(rightTypeCell)) {                    emptynum++;                }                rowlist.add(rightTypeCell);            }            if (emptynum == cells) {                return null;            }        } catch (Exception e) {            log.error("获取sheet表中第" + (rownum + 1) + "行信息集合失败", e);        }        return rowlist;    }    /**     * 读取excel所有数据信息     *     * @param sheet      sheet表     * @param totalRows  总行数     * @param totalCells 总列数     * @return 返回excel中的数据集合     */    private ArrayList<ArrayList<String>> readExcel(Sheet sheet, int totalRows, int totalCells) {        ArrayList<ArrayList<String>> conlumlist = new ArrayList<>();        for (int i = 1; i < totalRows; i++) {            ArrayList<String> perRowInfo = getPerRowInfo(i, totalCells, sheet);            if (perRowInfo != null) {                conlumlist.add(perRowInfo);            }        }        return conlumlist;    }    /**     * 将所读取数据的每行信息封装入map     *     * @param rownum   行数     * @param headList 头信息     * @param crows    已读取的数据信息     * @return 返回每行数据的map集合     */    private HashMap<String, String> PerRowInfoToMap(int rownum, List<String> headList,                                                    ArrayList<ArrayList<String>> crows) {        HashMap<String, String> permap = null;        try {            permap = new HashMap<>();            ArrayList<String> rowStr = crows.get(rownum);            for (int num = 0; num < headList.size(); num++) {                permap.put(headList.get(num).trim(), rowStr.get(num));            }        } catch (Exception e) {            log.error("将excel中第" + rownum + "行数据封装进map出错", e);        }        return permap;    }    /**     * @param cell 一个单元格的对象     * @return 返回该单元格相应的类型的值     */    private String getRightTypeCell(Cell cell) {        if (cell == null) {            return "";        }        String object = null;        switch (cell.getCellType()) {            case Cell.CELL_TYPE_NUMERIC: // 数字                if (HSSFDateUtil.isCellDateFormatted(cell)) {                    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");                    return sdf.format(HSSFDateUtil.getJavaDate(cell.getNumericCellValue())).toString();                } else {                    cell.setCellType(Cell.CELL_TYPE_STRING);                }                object = cell.getStringCellValue() + "";                break;            case Cell.CELL_TYPE_STRING: // 字符串                object = cell.getStringCellValue();                break;            case Cell.CELL_TYPE_BOOLEAN: // Boolean                object = cell.getBooleanCellValue() + "";                break;            case Cell.CELL_TYPE_FORMULA: // 公式                object = cell.getCellFormula() + "";                break;            case Cell.CELL_TYPE_BLANK: // 空值                object = "";                break;            case Cell.CELL_TYPE_ERROR: // 故障                object = "非法字符";                break;            default:                object = "未知类型";                break;        }        return object;    }    public static void main(String[] args) throws IllegalAccessException, InstantiationException {        String upload = "https://ohle6xur4.qnssl.com/o_1bcjm8tondu3hlpac110e0i2pe.xlsx";        String filePath = "/home/gmh/test1.xlsx";        String filePath1 = "/home/gmh/test2.xlsx";        long starttime = System.currentTimeMillis();        ExcelUtil excelUtil = new ExcelUtil(filePath);        List<Map<String, String>> head = excelUtil.getContents();        excelUtil.writeExcel(filePath1, head);        long endtime = System.currentTimeMillis();        log.info("工具类运行共耗时：" + (endtime - starttime) + "毫秒");    }}

参考文章：http://www.ituring.com.cn/article/9288