Java读取操作大数据excel

工作需要，读取大数据量的excel。用Apache poi的普通模式读取，会抛内存溢出。查询文档得知有另外一种模式--用户模式。该模式不会一下子整个文件load进来放在内存里，而是一行一行的读取，这样就能避免内存溢出了。

上码：

package com.ism.excel.pkg07;

import java.io.InputStream;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.poi.xssf.eventusermodel.XSSFReader;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.apache.poi.xssf.usermodel.XSSFRichTextString;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;

/**
 * XSSF and SAX (Event API)
 */
public abstract class XxlsAbstract extends DefaultHandler {
	private SharedStringsTable sst;
	private String lastContents;
	private boolean nextIsString;

	private int sheetIndex = -1;
	private List<String> rowlist = new ArrayList<String>();
	private int curRow = 0;		//当前行
	private int curCol = 0;		//当前列索引
	private int preCol = 0;		//上一列列索引
	private int titleRow = 0;	//标题行，一般情况下为0
	private int rowsize = 0;	//列数

	//excel记录行操作方法，以sheet索引，行索引和行元素列表为参数，对sheet的一行元素进行操作，元素为String类型
	public abstract void optRows(int sheetIndex,int curRow, List<String> rowlist) throws SQLException;

	//只遍历一个sheet，其中sheetId为要遍历的sheet索引，从1开始，1-3
	/**
	 *
	 * @param filename
	 * @param sheetId  sheetId为要遍历的sheet索引，从1开始，1-3
	 * @throws Exception
	 */
	public void processOneSheet(String filename,int sheetId) throws Exception {
		OPCPackage pkg = OPCPackage.open(filename);
		XSSFReader r = new XSSFReader(pkg);
		SharedStringsTable sst = r.getSharedStringsTable();

		XMLReader parser = fetchSheetParser(sst);

		// rId2 found by processing the Workbook
		// 根据 rId# 或 rSheet# 查找sheet
		InputStream sheet2 = r.getSheet("rId"+sheetId);
		sheetIndex++;
		InputSource sheetSource = new InputSource(sheet2);
		parser.parse(sheetSource);
		sheet2.close();
	}

	/**
	 * 遍历 excel 文件
	 */
	public void process(String filename) throws Exception {
		OPCPackage pkg = OPCPackage.open(filename);
		XSSFReader r = new XSSFReader(pkg);
		SharedStringsTable sst = r.getSharedStringsTable();

		XMLReader parser = fetchSheetParser(sst);

		Iterator<InputStream> sheets = r.getSheetsData();
		while (sheets.hasNext()) {
			curRow = 0;
			sheetIndex++;
			InputStream sheet = sheets.next();
			InputSource sheetSource = new InputSource(sheet);
			parser.parse(sheetSource);
			sheet.close();
		}
	}

	public XMLReader fetchSheetParser(SharedStringsTable sst)
			throws SAXException {
		XMLReader parser = XMLReaderFactory.createXMLReader();
				//.createXMLReader("org.apache.xerces.parsers.SAXParser");
		this.sst = sst;
		parser.setContentHandler(this);
		return parser;
	}

	public void startElement(String uri, String localName, String name,
			Attributes attributes) throws SAXException {
		// c => 单元格
		if (name.equals("c")) {
			// 如果下一个元素是 SST 的索引，则将nextIsString标记为true
			String cellType = attributes.getValue("t");
			String rowStr = attributes.getValue("r");
			curCol = this.getRowIndex(rowStr);
			if (cellType != null && cellType.equals("s")) {
				nextIsString = true;
			} else {
				nextIsString = false;
			}
		}
		// 置空
		lastContents = "";
	}

	public void endElement(String uri, String localName, String name)
			throws SAXException {
		// 根据SST的索引值的到单元格的真正要存储的字符串
		// 这时characters()方法可能会被调用多次
		if (nextIsString) {
			try {
				int idx = Integer.parseInt(lastContents);
				lastContents = new XSSFRichTextString(sst.getEntryAt(idx))
						.toString();
			} catch (Exception e) {

			}
		}

		// v => 单元格的值，如果单元格是字符串则v标签的值为该字符串在SST中的索引
		// 将单元格内容加入rowlist中，在这之前先去掉字符串前后的空白符
		if (name.equals("v")) {
			String value = lastContents.trim();
			value = value.equals("")?" ":value;
			int cols = curCol-preCol;
			if (cols>1){
				for (int i = 0;i < cols-1;i++){
					rowlist.add(preCol,"");
				}
			}
			preCol = curCol;
			rowlist.add(curCol-1, value);
		}else {
			//如果标签名称为 row ，这说明已到行尾，调用 optRows() 方法
			if (name.equals("row")) {
				int tmpCols = rowlist.size();
				if(curRow>this.titleRow && tmpCols<this.rowsize){
					for (int i = 0;i < this.rowsize-tmpCols;i++){
						rowlist.add(rowlist.size(), "");
					}
				}
				try {
					optRows(sheetIndex,curRow,rowlist);
				} catch (SQLException e) {
					e.printStackTrace();
				}
				if(curRow==this.titleRow){
					this.rowsize = rowlist.size();
				}
				rowlist.clear();
				curRow++;
				curCol = 0;
				preCol = 0;
			}
		}
	}

	public void characters(char[] ch, int start, int length)
			throws SAXException {
		//得到单元格内容的值
		lastContents += new String(ch, start, length);
	}

	//得到列索引，每一列c元素的r属性构成为字母加数字的形式，字母组合为列索引，数字组合为行索引，
	//如AB45,表示为第（A-A+1）*26+（B-A+1）*26列，45行
	public int getRowIndex(String rowStr){
		rowStr = rowStr.replaceAll("[^A-Z]", "");
		byte[] rowAbc = rowStr.getBytes();
		int len = rowAbc.length;
		float num = 0;
		for (int i=0;i<len;i++){
			num += (rowAbc[i]-'A'+1)*Math.pow(26,len-i-1 );
		}
		return (int) num;
	}

	public int getTitleRow() {
		return titleRow;
	}

	public void setTitleRow(int titleRow) {
		this.titleRow = titleRow;
	}
}