EasyExcel linux环境NullPointerException

原因：主要是因为Alpine Linux中OpenJDK无法使用字体控件fontconfig

解决方案：

1.将openjdk更换成oraclejdk

2.在dockerfile构建文件中，安装 fontconfig 和 ttf-dejavu字体。

3.开启内存处理模式，由于容易OOM需要慎重考虑。

EasyExcel.write(fileName, DemoData.class).inMemory(Boolean.TRUE).sheet("模板").doWrite(data());

报错：

[2022-11-22 19:06:14.916][http-nio-9121-exec-6][ERROR][DirectJDKLog:175][][]: Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
        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 java.lang.reflect.Constructor.newInstance(Constructor.java:423) [3 skipped]
        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:491)
        at java.awt.Font.canDisplayUpTo(Font.java:2060)
        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:273)
        at org.apache.poi.xssf.streaming.AutoSizeColumnTracker.<init>(AutoSizeColumnTracker.java:117)
        at org.apache.poi.xssf.streaming.SXSSFSheet.<init>(SXSSFSheet.java:82)
        at org.apache.poi.xssf.streaming.SXSSFWorkbook.createAndRegisterSXSSFSheet(SXSSFWorkbook.java:684)
        at org.apache.poi.xssf.streaming.SXSSFWorkbook.createSheet(SXSSFWorkbook.java:705)
        at org.apache.poi.xssf.streaming.SXSSFWorkbook.createSheet(SXSSFWorkbook.java:88)
        at com.alibaba.excel.util.WorkBookUtil.createSheet(WorkBookUtil.java:84)
        at com.alibaba.excel.context.WriteContextImpl.createSheet(WriteContextImpl.java:223)
        at com.alibaba.excel.context.WriteContextImpl.initSheet(WriteContextImpl.java:203)
        at com.alibaba.excel.context.WriteContextImpl.currentSheet(WriteContextImpl.java:135)
        at com.alibaba.excel.write.ExcelBuilderImpl.addContent(ExcelBuilderImpl.java:54)
        at com.alibaba.excel.ExcelWriter.write(ExcelWriter.java:70)
        at com.alibaba.excel.ExcelWriter.write(ExcelWriter.java:47)
        at com.alibaba.excel.write.builder.ExcelWriterSheetBuilder.doWrite(ExcelWriterSheetBuilder.java:62)
        at com.tencent.derive.midderive.web.util.EasyExcelUtil.download(EasyExcelUtil.java:74)
        at com.tencent.derive.midderive.web.derive.DeriveTaskController.downloadDeriveAsyncTask(DeriveTaskController.java:97)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [14 skipped]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [1 skipped]
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [2 skipped]
        at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:108) [10 skipped]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [20 skipped]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748) [1 skipped]