系統需要用到一個匯入excel檔案的功能，使用poi元件常規方式讀取excel時，記憶體耗盡，OutOfMemoryError,或者讀取非常慢
所以寫了一個工具類，使用poi sax方式讀取excel，速度快很多，記憶體消耗可以接受。

測試結果如下：
.xlsx檔案，35M大小，總4個sheel，
只讀取第一個，37434行，54列

總行數：37434
讀取耗時：39秒
列印耗時：17秒

主要程式碼如下：

ExcelUtils.class 主入口

package com.xxx.bi.utils.excel;

import java.util.List;
import java.util.Objects;

import org.apache.commons.lang3.StringUtils;

import com.google.common.collect.Lists;

public class ExcelUtils {
  /** logger日誌. */
  // public static final Logger LOGGER = Logger.getLogger(ExcelUtils.class);

  public ExcelUtils() {
  }

  /**
   * 獲取excel的表頭
   * 
   * @param filePath
   *      檔案路徑
   * @param headerNum
   *      表頭所在行數
   * @return
   */
  public static List<String> getHeader(String filePath,int headerNum) {
    if (StringUtils.isBlank(filePath)) {
      throw new IllegalArgumentException("傳入檔案路徑不能為空");
    }
    if (Objects.isNull(headerNum) || headerNum < 1) {
      headerNum = 1;
    }
    try {
      return LargeExcelFileReadUtil.getRowFromSheetOne(filePath,headerNum);
    } catch (Exception e) {
      // LOGGER.info("獲取excel[" + filePath + "]表頭失敗，原因:",e);
      e.printStackTrace();
    }
    return Lists.newArrayList();
  }

  /**
   * 獲取excel的所有資料<br/>
   * 所有資料型別都是String<br/>
   * 會以第一行資料的列數為總列數，所以第一行的資料必須都不為空，否則可能出java.lang.IndexOutOfBoundsException
   * 
   * @param filePath
   *      檔案路徑
   * @param headerNum
   *      表頭所在行數
   * @return
   */
  public static List<List<String>> getAllData(String filePath) {
    if (StringUtils.isBlank(filePath)) {
      throw new IllegalArgumentException("傳入檔案路徑不能為空");
    }
    try {
      return LargeExcelFileReadUtil.getRowsFromSheetOne(filePath);
    } catch (Exception e) {
      // LOGGER.info("獲取excel[" + filePath + "]表頭失敗，原因:",e);
      e.printStackTrace();
    }
    return Lists.newArrayList();
  }

  public static void main(String[] args) {
    long start = System.currentTimeMillis();
    String filepath = "C:/Users/Administrator/Desktop/05-作業調配表 -快遞.xlsx";
    // List<String> result = ExcelUtils.getHeader(filepath,1);
    // for (String col : result) {
    // System.out.println(col);
    // }

    List<List<String>> result = ExcelUtils.getAllData(filepath);
    long end = System.currentTimeMillis();
    for (List<String> list : result) {
      System.out.println(list.toString());
    }
    long end1 = System.currentTimeMillis();
    try {
      Thread.sleep(1000l);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    System.err.println("總行數：" + result.size());
    System.err.println(("讀取耗時：" + (end - start) / 1000) + "秒");
    System.err.println(("列印耗時：" + (end1 - end) / 1000) + "秒");
  }
}

LargeExcelFileReadUtil.class 真正的工具類

package com.xxx.bi.utils.excel;

import java.io.InputStream;
import java.util.List;
import java.util.Objects;

import org.apache.log4j.Logger;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.xssf.eventusermodel.XSSFReader;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;

public class LargeExcelFileReadUtil {
  /** logger日誌. */
  public static final Logger LOGGER = Logger.getLogger(LargeExcelFileReadUtil.class);

  // 處理一個sheet
  public static List<String> getRowFromSheetOne(String filename,Integer rowNum) throws Exception {
    InputStream inputStream = null;
    OPCPackage pkg = null;
    SingleRowHandler singleRowHandler = null;
    try {
      pkg = OPCPackage.open(filename);
      XSSFReader r = new XSSFReader(pkg);
      SharedStringsTable sst = r.getSharedStringsTable();
      singleRowHandler = new SingleRowHandler(sst,rowNum);
      XMLReader parser = XMLReaderFactory.createXMLReader("com.sun.org.apache.xerces.internal.parsers.SAXParser");
      parser.setContentHandler(singleRowHandler);
      inputStream = r.getSheet("rId1");
      InputSource sheetSource = new InputSource(inputStream);
      parser.parse(sheetSource);
      return singleRowHandler.getRow();
    } catch (Exception e) {
      String message = e.getMessage();
      if (Objects.nonNull(rowNum) && Objects.nonNull(singleRowHandler)
          && SingleRowHandler.FINISH_ROW_MESSAGE.equalsIgnoreCase(message)) {
        // 獲取某一行資料完成 ，暫時不知道怎麼能終止excel解析，直接丟擲了異常，實際是成功的
        return singleRowHandler.getRow();
      }
      throw e;
    } finally {
      if (Objects.nonNull(pkg)) {
        pkg.close();
      }
      if (Objects.nonNull(inputStream)) {
        inputStream.close();
      }
    }
  }

  // 處理一個sheet
  public static List<List<String>> getRowsFromSheetOne(String filename) throws Exception {
    InputStream inputStream = null;
    OPCPackage pkg = null;
    MultiRowHandler multiRowHandler = null;
    try {
      pkg = OPCPackage.open(filename);
      XSSFReader r = new XSSFReader(pkg);
      SharedStringsTable sst = r.getSharedStringsTable();
      multiRowHandler = new MultiRowHandler(sst);
      XMLReader parser = XMLReaderFactory.createXMLReader("com.sun.org.apache.xerces.internal.parsers.SAXParser");
      parser.setContentHandler(multiRowHandler);
      inputStream = r.getSheet("rId1");
      InputSource sheetSource = new InputSource(inputStream);
      parser.parse(sheetSource);
      return multiRowHandler.getRows();
    } catch (Exception e) {
      throw e;
    } finally {
      if (Objects.nonNull(pkg)) {
        pkg.close();
      }
      if (Objects.nonNull(inputStream)) {
        inputStream.close();
      }
    }
  }
}

SingleRowHandler.class 當行處理類，可以只獲取表頭或表格中的某一行資料

package com.xxx.bi.utils.excel;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.regex.Pattern;

import org.apache.poi.xssf.model.SharedStringsTable;
import org.apache.poi.xssf.usermodel.XSSFRichTextString;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class SingleRowHandler extends DefaultHandler {
  public final static String FINISH_ROW_MESSAGE = "row data process finish";

  private Integer rowNum = null;// rowNum不為空時則標示只需要獲取這一行的資料
  private int curRowNum = 1;
  private String cellType = "";
  private SharedStringsTable sst;
  private String lastContents;
  private boolean nextIsString;
  private String cellPosition;
  private List<String> row = new ArrayList<>();

  public List<String> getRow() {
    return row;
  }

  public SingleRowHandler(SharedStringsTable sst,Integer rowNum) {
    this.sst = sst;
    this.rowNum = rowNum;
  }

  public void startElement(String uri,String localName,String name,Attributes attributes) throws SAXException {
    if (name.equals("c")) {
      cellPosition = attributes.getValue("r");
      // 這是一個新行
      if (Pattern.compile("^A[0-9]+$").matcher(cellPosition).find()) {
        curRowNum = Integer.valueOf(cellPosition.substring(1));
      }
      cellType = "";
      cellType = attributes.getValue("t");
      if ("s".equals(cellType)) {
        nextIsString = true;
      } else {
        nextIsString = false;
      }
    }
    // 清楚快取內容
    lastContents = "";
    if (Objects.nonNull(rowNum) && curRowNum > rowNum) {
      // 獲取某一行資料完成 ，暫時不知道怎麼能終止excel解析，直接丟擲了異常，實際是成功的
      throw new SAXException(FINISH_ROW_MESSAGE);
    }
  }

  public void endElement(String uri,String name) throws SAXException {
    if (nextIsString) {
      int idx = Integer.parseInt(lastContents);
      lastContents = new XSSFRichTextString(sst.getEntryAt(idx)).toString();
      nextIsString = false;
    }

    if (name.equals("v")) {
      if (Objects.isNull(rowNum) || rowNum == curRowNum) {
        row.add(lastContents);
      }
    }
  }

  public void characters(char[] ch,int start,int length) throws SAXException {
    lastContents += new String(ch,start,length);
  }
}

MultiRowHandler.class 獲取excel所有行的資料

package com.xxx.bi.utils.excel;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.regex.Pattern;

import org.apache.commons.lang3.StringUtils;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.apache.poi.xssf.usermodel.XSSFRichTextString;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * 獲取完整excel資料的handler<br/>
 * 
 * @author Administrator
 *
 */
public class MultiRowHandler extends DefaultHandler {
  private int curRowNum = 0;// 行號，從1開始
  private int curColIndex = -1;// 列索引，從0開始
  private int colCnt = 0;// 列數，取第一行列數做為列總數
  private String cellType = "";
  private SharedStringsTable sst;
  private String lastContents;
  private boolean nextIsString;
  private String cellPosition;
  private List<String> head = null;
  private List<String> curRowData = null;
  private boolean curRowIsBlank = true;// 當前是個空行
  private List<List<String>> rows = new ArrayList<>();

  public List<List<String>> getRows() {
    return rows;
  }

  public MultiRowHandler(SharedStringsTable sst) {
    this.sst = sst;
  }

  @Override
  public void startElement(String uri,Attributes attributes) throws SAXException {
    if (name.equals("c")) {
      cellPosition = attributes.getValue("r");
      curColIndex = getColIndex(cellPosition);
      // 這是一個新行
      if (isNewRow(cellPosition)) {
        curRowNum = getRowNum(cellPosition);
        if (2 == curRowNum && Objects.nonNull(curRowData)) {
          head = curRowData;
          colCnt = head.size();
        }
        curRowData = getBlankRow(colCnt);
      }
      cellType = "";
      cellType = attributes.getValue("t");
      if ("s".equals(cellType)) {
        nextIsString = true;
      } else {
        nextIsString = false;
      }
    }
    // 清楚快取內容
    lastContents = "";
  }

  private boolean isNewRow(String cellPosition) {
    // 座標以A開頭，後面跟數字 或者座標行和當前行不一致的
    boolean newRow = Pattern.compile("^A[0-9]+$").matcher(cellPosition).find();
    if (!newRow) {
      int cellRowNum = getRowNum(cellPosition);
      newRow = (cellRowNum != curRowNum);
    }
    return newRow;
  }

  /**
   * 根據列座標獲取行號，從1開始，返回0時標示出錯
   * 
   * @param cellPosition
   *      列座標，為A1,B23等
   * @return 行號，從1開始，返回0是為失敗
   */
  private static int getRowNum(String cellPosition) {
    String strVal = Pattern.compile("[^0-9]").matcher(cellPosition).replaceAll("").trim();// 獲取座標中的數字
    if (StringUtils.isNotBlank(strVal)) {
      return Integer.valueOf(strVal);
    }
    return 0;
  }

  /**
   * 根據列座標返回當前列索引，從0開始，返回-1時標示出錯<br/>
   * A1->0; B1->1...AA1->26
   * 
   * @param cellPosition
   *      列座標，為A1,B23等
   * @return 列索引，從0開始，返回-1是為失敗,A1->0; B1->1...AA1->26
   */
  private static int getColIndex(String cellPosition) {
    int index = -1;
    int num = 65;// A的Unicode碼
    int length = cellPosition.length();
    for (int i = 0; i < length; i++) {
      char c = cellPosition.charAt(i);
      if (Character.isDigit(c)) {
        break;// 確定指定的char值是否為數字
      }
      index = (index + 1) * 26 + (int) c - num;
    }
    return index;
  }

  /**
   * 返回一個全部為空字串的空行
   * 
   * @param cnt
   * @return
   */
  private List<String> getBlankRow(int cnt) {
    List<String> result = new ArrayList<>(cnt);
    for (int i = 0; i < cnt; i++) {
      result.add(i,"");
    }
    curRowIsBlank = true;
    return result;
  }

  @Override
  public void endElement(String uri,String name) throws SAXException {
    if (nextIsString) {
      int idx = Integer.parseInt(lastContents);
      lastContents = new XSSFRichTextString(sst.getEntryAt(idx)).toString();
      nextIsString = false;
    }

    if (name.equals("v")) {
      // System.out.println(MessageFormat.format("當前列定位:{0},當前行:{1},當前列:{2},當前值:{3}",// cellPosition,curRowNum,// curColIndex,lastContents));
      if (Objects.isNull(head)) {
        curRowData.add(lastContents);
      } else {
        curRowData.set(curColIndex,lastContents);
      }
      curRowIsBlank = false;
      // 這是一個新行
      if (isNewRow(cellPosition)) {
        if (Objects.nonNull(curRowData)) {
          if (curRowIsBlank) {
            curRowData.clear();// 如果當前行是空行，則清空當前行資料
          }
          rows.add(curRowData);
        }
      }

    }
  }

  @Override
  public void endDocument() throws SAXException {
    if (Objects.nonNull(curRowData) && !curRowIsBlank) {
      rows.add(curRowData);// 最後一行在上面不好加入,最後一行全是空行的不加入
    }
    super.endDocument();
  }

  @Override
  public void characters(char[] ch,length);
  }

  @Override
  public void ignorableWhitespace(char[] ch,int length) throws SAXException {
    lastContents += "";
  }

  public static void main(String[] args) {
    System.out.println(getColIndex("BC2"));
  }
}

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。