POI 生成excel(大数据量) SXSSF

使用POI 的SXSSF (Streaming Usermodel API)生成较大的excel，同时开启压缩

 import junit.framework.Assert;
 import org.apache.poi.ss.usermodel.Cell;
 import org.apache.poi.ss.usermodel.Row;
 import org.apache.poi.ss.usermodel.Sheet;
 import org.apache.poi.ss.usermodel.Workbook;
 import org.apache.poi.ss.util.CellReference;
 import org.apache.poi.xssf.streaming.SXSSFWorkbook;

     public static void main(String[] args) throws Throwable {
         SXSSFWorkbook wb = new SXSSFWorkbook(100); // keep 100 rows in memory, exceeding rows will be flushed to disk
         Sheet sh = wb.createSheet();
         for(int rownum = 0; rownum < 1000; 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("/temp/sxssf.xlsx");
         wb.write(out);
         out.close();

         // dispose of temporary files backing this workbook on disk
         wb.dispose();
     }

遇到的问题：

错误是NPE错误，类似如下，原因是缺少字体或者环境变量未设置，需要安装"ttf-dejavu"字体，具体可以参考：

https://stackoverflow.com/questions/30626136/cannot-load-font-in-jre-8

https://www.jianshu.com/p/c05b5fc71bd0

 java.lang.NullPointerException
     at sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1264)
     at sun.awt.FontConfiguration.readFontConfigFile(FontConfiguration.java:219)
     at sun.awt.FontConfiguration.init(FontConfiguration.java:107)
     at sun.awt.X11FontManager.createFontConfiguration(X11FontManager.java:774)
     at sun.font.SunFontManager$2.run(SunFontManager.java:431)
     at java.security.AccessController.doPrivileged(Native Method)
     at sun.font.SunFontManager.<init>(SunFontManager.java:376)
     at sun.awt.FcFontManager.<init>(FcFontManager.java:35)
     at sun.awt.X11FontManager.<init>(X11FontManager.java:57)
     at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
     at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
     at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
     at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
     at java.lang.Class.newInstance(Class.java:442)
     at sun.font.FontManagerFactory$1.run(FontManagerFactory.java:83)
     at java.security.AccessController.doPrivileged(Native Method)
     at sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:74)
     at java.awt.Font.getFont2D(Font.java:495)
     at java.awt.Font.canDisplayUpTo(Font.java:2080)
     at java.awt.font.TextLayout.singleFont(TextLayout.java:470)
     at java.awt.font.TextLayout.<init>(TextLayout.java:531)
     at org.apache.poi.ss.util.SheetUtil.getDefaultCharWidth(SheetUtil.java:275)
     at org.apache.poi.xssf.streaming.AutoSizeColumnTracker.<init>(AutoSizeColumnTracker.java:117)
     at org.apache.poi.xssf.streaming.SXSSFSheet.<init>(SXSSFSheet.java:79)
     at org.apache.poi.xssf.streaming.SXSSFWorkbook.createAndRegisterSXSSFSheet(SXSSFWorkbook.java:656)
     at org.apache.poi.xssf.streaming.SXSSFWorkbook.createSheet(SXSSFWorkbook.java:677)
     at org.apache.poi.xssf.streaming.SXSSFWorkbook.createSheet(SXSSFWorkbook.java:83)

还有一种，easyexcel，没用过，可以参考https://github.com/alibaba/easyexcel