在实际项目中，经常会用到POI3.8来导出excel。而导出excel的时候，会因为残留大量以.xml结尾的文件而导致服务器存储空间急剧增长，最后导致系统挂了。为此，该怎么办呢？
.xml后缀残留文件示例
通过大量的翻阅资料，目前有两种解决方式：
方式1：手动清除临时文件
POI3.8并没有提供方法来清除临时文件，为此，这里可以自己手动进行清除：
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi</artifactId>
<version>3.9</version>
</dependency>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.9</version>
</dependency>
package com.jack.shx.MySpringBoot; import java.io.File; import java.lang.reflect.Field; import org.apache.poi.ss.usermodel.Sheet; import org.apache.poi.xssf.streaming.SXSSFSheet; import org.apache.poi.xssf.streaming.SXSSFWorkbook; import org.apache.poi.xssf.streaming.SheetDataWriter; public class SXSSFTempFilesDelete { /*** * Returns a private attribute of a class * @param containingClass The class that contains the private attribute to retrieve * @param fieldToGet the name of the attribute to get * @return The private attribute * @throws NoSuchFieldException * @throws IllegalAccessException */ public static Object getPrivateAttribute( Object containingClass, String fieldToGet) throws NoSuchFieldException, IllegalAccessException { // get the field of the containingClass instance Field declaredField = containingClass.getClass().getDeclaredField(fieldToGet); declaredField.setAccessible(true); // access it Object get = declaredField.get(containingClass); // return it! return get; } /*** * Deletes all temporary files of the SXSSFWorkbook instance * @param workbook * @throws NoSuchFieldException * @throws IllegalAccessException */ public static void deleteSXSSFTempFiles(SXSSFWorkbook workbook) throws NoSuchFieldException, IllegalAccessException { int numberOfSheets = workbook.getNumberOfSheets(); // iterate through all sheets (each sheet as a temp file) for (int i = 0; i <= numberOfSheets; i++) { Sheet sheetAt = workbook.getSheetAt(i); // delete only if the sheet is written by stream if (sheetAt instanceof SXSSFSheet) { SheetDataWriter sdw = (SheetDataWriter) getPrivateAttribute(sheetAt, "_writer"); File f = (File) getPrivateAttribute(sdw, "_fd"); try { f.delete(); } catch (Exception ex) { // could not delete the file } } } } }
或者
方式2：将POI3.8替换成更高的版本，并利用dispose方法清除临时文件
目前，更高版本的POI已经提供了清除临时文件的方法，具体可以参考官网：http://poi.apache.org/apidocs/org/apache/poi/xssf/streaming/SXSSFWorkbook.html
此时，我们在使用的时候就可以方便的清除临时文件，避免空间爆满了：
/** * 大数据量导出 * @throws IOException */ @Test public void text2() throws IOException { XSSFWorkbook xssfWorkbook = new XSSFWorkbook(Thread.currentThread().getContextClassLoader().getResourceAsStream("bigdata.xlsx")); SXSSFWorkbook wb = new SXSSFWorkbook(xssfWorkbook, 1000); //内存中保留 1000 条数据，以免内存溢出，其余写入 硬盘 专门处理大数据 Sheet sh = wb.getSheetAt(0); for(int rownum = 1; rownum < 75537; rownum++){ 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); } } // // Rows with rownum < 900 are flushed and not accessible // for(int rownum = 0; rownum < 900; rownum++){ // Assert.assertNull(sh.getRow(rownum)); // } // // // ther last 100 rows are still in memory // for(int rownum = 900; rownum < 1000; rownum++){ // Assert.assertNotNull(sh.getRow(rownum)); // } FileOutputStream out = new FileOutputStream("D:\\sxssf.xlsx"); wb.write(out); out.close(); // dispose of temporary files backing this workbook on disk wb.dispose();
请注意 就这个一句话 wb.dispose();
