fix: 空指针异常

Author: 尤志强

easyexcel-core/src/main/java/com/alibaba/excel/metadata/csv/CsvSheet.java

@@ -136,9 +136,12 @@ public void removeRow(Row row) {
 
     @Override
     public Row getRow(int rownum) {
+        if (rowCache == null) {
+            return null;
+        }
         int actualRowIndex = rownum - (lastRowIndex - rowCache.size()) - 1;
         if (actualRowIndex < 0 || actualRowIndex > rowCache.size() - 1) {
-            throw new UnsupportedOperationException("The current data does not exist or has been flushed to disk\n.");
+            return null;
         }
         return rowCache.get(actualRowIndex);
     }

easyexcel-test/src/test/java/com/alibaba/easyexcel/test/demo/rare/CsvTest.java

@@ -0,0 +1,60 @@
+package com.alibaba.easyexcel.test.demo.rare;
+
+import com.alibaba.easyexcel.test.util.TestFileUtil;
+import com.alibaba.excel.EasyExcel;
+import com.alibaba.excel.ExcelWriter;
+import com.alibaba.excel.write.handler.SheetWriteHandler;
+import com.alibaba.excel.write.metadata.WriteSheet;
+import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
+import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.poi.ss.usermodel.Sheet;
+import org.junit.jupiter.api.Test;
+
+import org.apache.poi.ss.usermodel.Row;
+
+import org.apache.poi.ss.usermodel.Cell;
+
+import java.util.Collections;
+
+/**
+ * @author youzhiqiang
+ * @date 2024/6/14
+ */
+@Slf4j
+public class CsvTest {
+
+
+    @Test
+    public void customer() {
+        String fileName = TestFileUtil.getPath() + "sheetWriteHandlerForCsv" + System.currentTimeMillis() + ".csv";
+        // 这里 需要指定写用哪个class去写
+        ExcelWriter excelWriter = EasyExcel.write(fileName)
+                .registerWriteHandler(new SheetWriteHandler() {
+                    @Override
+                    public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
+                        Sheet sheet = writeSheetHolder.getSheet();
+
+                        for (int column = 0; column < 10; column++) {
+                            for (int rowIndex = 0; rowIndex < 20; rowIndex++) {
+                                Row row = sheet.getRow(rowIndex);
+                                if (row == null) {
+                                    row = sheet.createRow(rowIndex);
+                                }
+
+                                Cell cell = row.getCell(column);
+                                if (cell == null) {
+                                    cell = row.createCell(column);
+                                }
+                                cell.setCellValue("测试" + column + ":" + rowIndex);
+                            }
+                        }
+                    }
+                })
+                .build();
+        WriteSheet writeSheet = EasyExcel.writerSheet("模板").build();
+        excelWriter.write(Collections.emptyList(), writeSheet);
+        excelWriter.finish();
+    }
+
+}