今天在做excel文件上传时，发现数据量超过10万条后，系统会出现内存溢出。
跟踪代码发现程序卡在如下代码这里：
Workbook workbook=WorkbookFactory.create(new File(path));通过poi的api发现此方法属于能对excel读写，但是内存消耗大，速度较慢。
在poi的官方文档中找到了读取大量数据的方法，但只能读数据，不能进行写操作。
代码整理如下
import java.io.InputStream;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.xssf.eventusermodel.XSSFReader;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.apache.poi.xssf.usermodel.XSSFRichTextString;
import org.junit.Test;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
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;
/**
* 数据量比较大(8万条以上)的excel文件解析，将excel文件解析为 行列坐标-值的形式存入map中，此方式速度快，内存耗损小 但只能读取excle文件
* 提供处理单个sheet方法 processOneSheet(String filename) 以及处理多个sheet方法 processAllSheets(String filename)
* 只需传入文件路径+文件名即可 调用处理方法结束后，只需 接收LargeExcelFileReadUtil.getRowContents()返回值即可获得解析后的数据
*
*/
public class LargeExcelFileReadUtil {
private LinkedHashMap<String, String>rowContents=new LinkedHashMap<String, String>();
private SheetHandler sheetHandler;
public LinkedHashMap<String, String> getRowContents() {
return rowContents;
}
public void setRowContents(LinkedHashMap<String, String> rowContents) {
this.rowContents = rowContents;
}
public SheetHandler getSheetHandler() {
return sheetHandler;
}
public void setSheetHandler(SheetHandler sheetHandler) {
this.sheetHandler = sheetHandler;
}
//处理一个sheet
public void processOneSheet(String filename) throws Exception {
InputStream sheet2=null;
OPCPackage pkg =null;
try {
pkg = OPCPackage.open(filename);
XSSFReader r = new XSSFReader(pkg);
SharedStringsTable sst = r.getSharedStringsTable();
XMLReader parser = fetchSheetParser(sst);
sheet2 = r.getSheet("rId1");
InputSource sheetSource = new InputSource(sheet2);
parser.parse(sheetSource);
setRowContents(sheetHandler.getRowContents());
}catch (Exception e) {
e.printStackTrace();
throw e;
}finally{
if(pkg!=null){
pkg.close();
}
if(sheet2!=null){
sheet2.close();
}
}
}
//处理多个sheet
public void processAllSheets(String filename) throws Exception {
OPCPackage pkg =null;
InputStream sheet=null;
try{
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()) {
System.out.println("Processing new sheet:\n");
sheet = sheets.next();
InputSource sheetSource = new InputSource(sheet);
parser.parse(sheetSource);
}
}catch (Exception e) {
e.printStackTrace();
throw e;
}finally{
if(pkg!=null){
pkg.close();
}
if(sheet!=null){
sheet.close();
}
}
}
public XMLReader fetchSheetParser(SharedStringsTable sst) throws SAXException {
XMLReader parser =
XMLReaderFactory.createXMLReader(
"com.sun.org.apache.xerces.internal.parsers.SAXParser"
);
setSheetHandler(new SheetHandler(sst));
ContentHandler handler = (ContentHandler) sheetHandler;
parser.setContentHandler(handler);
return parser;
}
/**
* See org.xml.sax.helpers.DefaultHandler javadocs
*/
//测试
@Test
public void test ()throws Exception {
Long time=System.currentTimeMillis();
LargeExcelFileReadUtil example = new LargeExcelFileReadUtil();
example.processOneSheet("C:/Users/Desktop/2018041310024112.xlsx");
Long endtime=System.currentTimeMillis();
LinkedHashMap<String, String> map=example.getRowContents();
Iterator<Entry<String, String>> it= map.entrySet().iterator();
int count=0;
String prePos="";
while (it.hasNext()){
Map.Entry<String, String> entry=(Map.Entry<String, String>)it.next();
String pos=entry.getKey();
if(!pos.substring(1).equals(prePos)){
prePos=pos.substring(1);
count++;
}
System.out.println(pos+";"+entry.getValue());
}
System.out.println("解析数据"+count+"条;耗时"+(endtime-time)/1000+"秒");
}
}
/**
SheetHandler 类中处理从excle获取的数据，官方文档中 SheetHandler以内部类形式，为保证更新代码减少内部类class文件忘记打包，改为一般java类
*/
import java.util.LinkedHashMap;
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 SheetHandler extends DefaultHandler{
private SharedStringsTable sst;
private String lastContents;
private boolean nextIsString;
private String cellPosition;
private LinkedHashMap<String, String>rowContents=new LinkedHashMap<String, String>();
public LinkedHashMap<String, String> getRowContents() {
return rowContents;
}
public void setRowContents(LinkedHashMap<String, String> rowContents) {
this.rowContents = rowContents;
}
public SheetHandler(SharedStringsTable sst) {
this.sst = sst;
}
public void startElement(String uri, String localName, String name,
Attributes attributes) throws SAXException {
if(name.equals("c")) {
// System.out.print(attributes.getValue("r") + " - ");
cellPosition=attributes.getValue("r");
String cellType = attributes.getValue("t");
if(cellType != null && cellType.equals("s")) {
nextIsString = true;
} else {
nextIsString = false;
}
}
// 清楚缓存内容
lastContents = "";
}
public void endElement(String uri, String localName, 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("lastContents:"+cellPosition+";"+lastContents);
//数据读取结束后，将单元格坐标,内容存入map中
if(!(cellPosition.length()==2)||(cellPosition.length()==2&&!"1".equals(cellPosition.substring(1)))){//不保存第一行数据
rowContents.put(cellPosition, lastContents);
}
}
}
public void characters(char[] ch, int start, int length)
throws SAXException {
lastContents += new String(ch, start, length);
}
}
亲测可用，20多万条数据，4秒解析完，执行结果
poi jar包如下：
