java向excel 写入海量数据内存溢出问题的解决

java向excel 写入海量数据内存溢出问题的解决

由于项目中有导出海量数据的需求，在谷歌和百度也没有找到好的解决办法，经过仔细研究发现poi-3.8版本以上提供新的模式可以满足这个需求。

以下是测试代码:

import java.io.FileOutputStream;

import ng.exception.ExceptionUtils;import ermodel.Cell;import ermodel.Row;import ermodel.Sheet;import ermodel.Workbook;import org.apache.poi.ss.util.CellReference;import

org.apache.poi.xssf.streaming.SXSSFWorkbook;import

ermodel.XSSFWorkbook;

public class Test {

/*** @param args*/public static void main(String[] args) {if (args[0].equals("hssf")) {hssfTest();}if (args[0].equals("sxssf")) {sxssfTest();}

}

public static void sxssfTest() {Workbook wb = new SXSSFWorkbook(100); // keep 100 rows in memory,// exceeding rows will be// flushed to diskSheet sh = wb.createSheet();int rownum = 0;try {while (true) {Row row = sh.createRow(rownum);for (int cellnum = 0; cellnum < 10; cellnum++) {Cell cell = row.createCell(cellnum);String address = new CellReference(cell).formatAsString();cell.setCellValue(address);}System.out.println(rownum );rownum++;if (rownum >= 1000000)break;}

FileOutputStream out = new FileOutputStream("c:/sxssf.xlsx");wb.write(out);out.close();} catch (Exception e) {System.out.println(ExceptionUtils.getFullStackTrace(e));}

}

public static void hssfTest() {XSSFWorkbook wb = new XSSFWorkbook();Sheet sh = wb.createSheet();int rownum = 0;try {while (true) {Row row = sh.createRow(rownum);for (int cellnum = 0; cellnum < 10; cellnum++) {Cell cell = row.createCell(cellnum);String address = new CellReference(cell).formatAsString();cell.setCellValue(address);}System.out.println(rownum );rownum++;if (rownum >= 1000000)break;}

FileOutputStream out = new FileOutputStream("c:/hssf.xlsx");wb.write(out);out.close();} catch (Exception e) {System.out.println(ExceptionUtils.getFullStackTrace(e));}}}

将工程打包成jar到C：，然后用命令行java -jar -Xms128m -Xmx512m -XX:PermSize=128M -XX:MaxPermSize=512M test.jar hssf 执行，在命令行窗口输出到45000之后，输出明显减慢，

很快输出如下异常：

5028850289502905029150292Exception i n thread “main” ng.reflect.InvocationTargetExceptionat

sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at ng.reflect.Method.invoke(Method.java:585)at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)Caused by:

ng.OutOfMemoryError: Java heap space

继续用命令行java -jar -Xms128m -Xmx512m -XX:PermSize=128M -XX:MaxPermSize=512M test.jar sxssf执行，

命令行窗口输出速度一直保持不变，直到循环完了，并最终生成四十多M的excel—sxssf.xlsx