优化Excel自定义格式样式重复创建问题

ruoyi-common/ruoyi-common-core/src/main/java/com/ruoyi/common/core/utils/poi/ExcelUtil.java

@@ -79,6 +79,11 @@ public class ExcelUtil<T>
 
     public static final String[] FORMULA_STR = { "=", "-", "+", "@" };
 
+    /**
+     * 单元格样式缓存
+     */
+    private Map<String, CellStyle> cellStyleCache = new HashMap<String, CellStyle>();
+
     /**
      * Excel sheet最大行数，默认65536
      */
@@ -1042,9 +1047,16 @@ public class ExcelUtil<T>
      */
     private CellStyle createCellStyle(CellStyle cellStyle, String format)
     {
+        String key = cellStyle.getIndex() + "|" + format;
+        CellStyle cached = cellStyleCache.get(key);
+        if (cached != null)
+        {
+            return cached;
+        }
         CellStyle style = wb.createCellStyle();
         style.cloneStyleFrom(cellStyle);
         style.setDataFormat(wb.getCreationHelper().createDataFormat().getFormat(format));
+        cellStyleCache.put(key, style);
         return style;
     }