fix: fix Copilot review issue

Author: milixiang

fesod/src/main/java/org/apache/fesod/excel/write/executor/AbstractExcelWriteExecutor.java

@@ -161,13 +161,16 @@ protected void converterAndSet(CellWriteHandlerContext cellWriteHandlerContext)
                 Object o = dynamicColumnMap.get(key);
                 String originalVariable = cellWriteHandlerContext.getOriginalVariable();
                 if(originalVariable.contains(".")){
-                    key = originalVariable.split("\\.")[1];
-                    Object itemBean = o;
-                    if (null == itemBean) {
-                        o = null;
-                    }else{
-                        BeanMap beanMap = BeanMapUtils.create(itemBean);
-                        o = beanMap.get(key);
+                    int dotIndex = originalVariable.indexOf('.');
+                    if (dotIndex > 0) {
+                        key = originalVariable.substring(dotIndex + 1);
+                        Object itemBean = o;
+                        if (null == itemBean) {
+                            o = null;
+                        }else{
+                            BeanMap beanMap = BeanMapUtils.create(itemBean);
+                            o = beanMap.get(key);
+                        }
                     }
                 }
 

fesod/src/main/java/org/apache/fesod/excel/write/executor/ExcelWriteFillExecutor.java

@@ -173,7 +173,11 @@ private void shiftCellsIfNecessary(FillConfig fillConfig, Collection<?> collecti
                 List<String> variableList = analysisCell.getVariableList();
                 for (String fieldName : dynamicFieldMap.keySet()) {
                     for (String variable : variableList) {
-                        String variableFieldName = variable.split("\\.")[0];
+                        int dotIndex = variable.indexOf('.');
+                        if (dotIndex <= 0) {
+                            continue;
+                        }
+                        String variableFieldName = variable.substring(0, dotIndex);
                         if (StringUtils.equals(fieldName, variableFieldName)) {
                             List<String> headers = fillConfig.getDynamicColumnInfo(fieldName).getKeys();
                             Integer columnGroupSize = fillConfig.getDynamicColumnInfo(fieldName).getGroupSize();
@@ -280,7 +284,10 @@ private void doFill(
                 } else if (dataKeySet.contains(variable)) {
                     value = dataMap.get(variable);
                 } else if (variable.contains(COLLECTION_PREFIX)) {
-                    variable = variable.split("\\.")[0];
+                    int dotIndex = variable.indexOf('.');
+                    if (dotIndex > 0) {
+                        variable = variable.substring(0, dotIndex);
+                    }
                     value = dataMap.get(variable);
                 }
                 ExcelContentProperty excelContentProperty = ClassUtils.declaredExcelContentProperty(
@@ -479,7 +486,7 @@ private void createCell(
             cellWriteHandlerContext.getCellMap().put(lastRowIndex + "_" + lastColumnIndex, cellWriteHandlerContext);
             DynamicColumnInfo dynamicColumnInfo = fillConfig.getDynamicColumnInfo(field.getName());
             if (null == dynamicColumnInfo || CollectionUtils.isEmpty(dynamicColumnInfo.getKeys())) {
-                throw new ExcelGenerateException(String.format("Plase set dynamic column keys for %s in fillConfig", field.getName()));
+                throw new ExcelGenerateException(String.format("Please set dynamic column keys for %s in fillConfig", field.getName()));
             }
             for (int i = 1; i < dynamicColumnInfo.getKeys().size(); i++) {
                 switch (fillConfig.getDirection()) {

fesod/src/main/java/org/apache/fesod/excel/write/metadata/fill/FillConfig.java

@@ -77,6 +77,9 @@ public class FillConfig {
      * @return dynamic column info
      * */
     public DynamicColumnInfo getDynamicColumnInfo(String fieldName) {
+        if (null == dynamicColumnInfoMap) {
+            return null;
+        }
         if (null == fieldName || !dynamicColumnInfoMap.containsKey(fieldName)) {
             return dynamicColumnInfoMap.get(DEFAULT_DYNAMIC_INFO_KEY);
         }else{